FIRE AND SMOKE PROTECTION FEATURES

Section 703 Fire-Resistance Ratings and Fire Tests

Section 704 Fire-Resistance Rating of Structural Members

Section 705 Exterior Walls

Section 706 Fire Walls

Section 707 Fire Barriers

Section 708 Fire Partitions

Section 709 Smoke Barriers

Section 710 Smoke Partitions

Section 711 Floor and Roof Assemblies

Section 712 Vertical Openings

Section 713 Shaft Enclosures

Section 714 Penetrations

Section 715 Joint Systems

Section 716 Opening Protectives

Section 717 Ducts and Air Transfer Openings

Section 718 Concealed Spaces

Section 719 Fire-Resistance Requirements for Plaster

Section 720 Thermal- and Sound-Insulating Materials

Section 721 Prescriptive Fire Resistance

Section 722 Calculated Fire Resistance

Key Points

Section 703 Fire-Resistance Ratings and Fire Tests

It is the intent of the IBC that materials and methods used for fire-resistance purposes are limited to those specified in this chapter. Materials and assemblies tested in accordance with ASTM E 119 or UL 263 are considered to be in full compliance with the code, as are building components whose fire-resistance rating has been achieved by one of the alternative methods specified in Section 703.3.

703.2   Fire-resistance ratings.   This section indicates that building elements are considered to have a fire-resistance rating when tested in accordance with the procedures of ASTM E 119 or UL 263. Figures 703-1 through 703-5 depict the fundamental testing requirements of the two standards. The intent of the IBC is that any material or assembly that successfully passes the end-point criteria depicted for the specified time period shall have its fire-endurance rating accepted and the assembly classified in accordance with the time during which the assembly successfully withstood the test.

Figure 703-1   Test furnaces.

Figure 703-2   Floor assembly fire test.

Figure 703-3   Conditions of acceptance—wall fire test.

Figure 703-4   Combustible assembly for determining finish rating.

Figure 703-5   Alternative fire test of steel column protection.

Although early fire testing in the United States began as long ago as the 1890s, the standard fire-endurance test procedure using a standard time-temperature curve and specifying fire-endurance ratings in hours was developed in 1918. The significance of 1918 and later standards is the fact that they were and are intended to be reproducible so that the test conducted at one testing facility can be compared with the test of the same assembly conducted at any other testing facility. An often-expressed criticism of a standard such as ASTM E 119 or UL 263 is that “it does not represent the real world.” This is true in many cases, and for that reason it should not be thought of as representing the absolute behavior of a fire-resistance-rated assembly under most actual fires in buildings. There are too many variables that affect the fire endurance of an assembly during an actual fire, such as fuel load, room size, rate of oxygen supply, and restraint, to consider that the test establishes absolute values of the real-world fire endurance of an assembly. However, it is a severe test of the fire-resistive qualities of a material or an assembly, and because of its reproducibility, it provides a means of comparing assemblies.

In addition to the fire-endurance fire ratings obtained from the standard fire tests of ASTM E 119 and UL 263, it is also possible to obtain, as expressed in the standard, the protective membrane performance for walls, partitions, and floor or roof assemblies. In the case of combustible walls or floor or roof assemblies, it is also referred to as the finish rating. Although the test standard does not limit the determination of the protective membrane performance to combustible assemblies, its greatest significance is with combustible assemblies.

The end-point criteria for determining the finish rating are that the average temperature at the surface of the protected materials shall not be greater than 250°F (121°C) above the beginning temperature. Furthermore, the maximum temperature at any measured point shall not be greater than 325°F (163°C) above the beginning temperature. These temperatures relate to the lower limit of ignition temperatures for wood. Figure 703-4 illustrates the determination of the finish rating for a wall assembly, which is usually determined during a fire-endurance test of the assembly.

The conditions of acceptance, also referred to as failure criteria and end-point criteria, of fire-resistance-rated assemblies are as follows:

1.   For load-bearing assemblies, the applied load must be successfully sustained during the time period for which classification is desired. There shall be no passage of flame or gases hot enough to ignite cotton waste on the unexposed surfaces.

2.   The average temperature rise on the unexposed surface shall not be more than 250°F (121°C) above the initial temperature during the time period of the test.

3.   The maximum temperature on the unexposed surface shall not be more than 325°F (163°C) above the initial temperature during the time period of the test.

4.   Walls or partitions shall withstand the hose-stream test without passage of flame or gases hot enough to ignite cotton waste on the unexposed side or the projection of water from the hose stream beyond the unexposed surface.

In addition to the conditions of acceptance just described, load-carrying structural members in roof and floor assemblies are subject to special end-point temperatures for:

1.   Structural steel beams and girders—1,100°F (593°C) average at any cross section and 1,300°F (704°C) for any individual thermocouple, for unrestrained assemblies.

2.   Reinforcing steel in cast-in-place reinforced concrete beams and girders—1,100°F (593°C) average at any section.

3.   Prestressing steel in prestressed concrete beams and girders—800°F (427°C) average at any section.

4.   Steel deck floor and roof units—1,100°F (593°C) average on any one span.

As columns are exposed to fire on all surfaces, the standard has special temperature and testing criteria for these members:

1.   The column is loaded so as to develop (as nearly as practicable) the working stresses contemplated by the structural design. The condition of acceptance is simply that the column sustain the load for the duration of the test period for which a classification is desired.

2.   Alternatively, a steel column may be tested without load, and the column will be tested in the furnace to determine the adequacy of the protection on the steel column. The test and end points are depicted in Figure 703-5.

The exception to this section is intended to modify the acceptance criteria for exterior bearing walls so that the walls will receive a rating based on which of the two following sets of criteria occurs first during the test:

1.   Heat transmission or flame and hot gases transmission for nonbearing walls.

2.   Structural failure or hose-stream application failure.

The first set of end points measures the wall’s ability to prevent the spread of fire from one side to the opposite side. It is considered overly restrictive to require that exterior bearing walls comply with this first set of end points for a longer time than would be required for a nonbearing wall located at the same distance from the lot line if it is still structurally capable of carrying the superimposed loads.

703.2.1   Nonsymmetrical wall construction.   At times, an interior wall or partition is constructed nonsymmetrically as far as its fire protection is concerned, with the membrane on one side of the wall differing from that on the opposing side. Where the wall is to be fire-resistance rated, it must be tested from both sides in order to determine the fire-resistance rating to be assigned to the assembly. Based on the two tests, the shortest time period is determined to be the wall’s rating. An assembly tested from only one side may be approved by the building official, provided there is adequate evidence furnished to show that the wall was tested with the least fire-resistive side exposed to the furnace. The provisions for exterior walls of nonsymmetrical construction differ somewhat from those addressing interior walls and are regulated by Section 705.5.

703.2.3   Restrained classification.   A dual classification system is used in ASTM E 119 and UL 263 for roof and floor assemblies, including their structural members. This dual classification system involves the use of the terms restrained and unrestrained. The use of the word restrained entails the concept of thermal restraint (restrained against thermal expansion as well as against rotation at the ends of an assembly or structural member).

For example, if a structural beam of a uniform cross section is subjected to heat on its bottom surface, such as would be the case in the standard test furnace, it will attempt to expand in all directions with the longitudinal expansion being the primary component. If the beam is restrained at the ends so that it cannot expand, compressive stresses will build up within the beam, and it will in effect behave in similar fashion as a prestressed beam. As a result, the thermal restraint will be beneficial in terms of improving the beam’s ability to sustain the applied load during the fire test. If the same beam is restrained only for the lower one-half of its cross section, it will tend to deflect upward owing to the conditions of restraint. This upward deflection tendency is also considered to enhance the beam’s ability to sustain the applied load during a fire-endurance test.

Conversely, if the end restraint is applied only to the upper half of the beam’s cross section, the beam will tend to deflect downward and, in this case, the restraint will be detrimental to the beam’s ability to sustain the applied load during the fire-endurance test. As the heat is applied to the bottom surface during a fire, it creates a downward deflection, and the two downward deflections are additive. In an actual building, this could lead to premature failure. It can be seen, then, that thermal restraint may be either beneficial or detrimental to the fire-resistant assembly, depending on its means of application in the building.

General guidance for the building official is provided in ASTM E 119 and UL 263 as to what conditions in the constructed building provide restraint. It is generally agreed that an interior panel of a monolithically cast-in-place reinforced-concrete floor slab would be considered to have thermal restraint. Also, Footnote k to Table 721.1(1) provides that “interior spans of continuous slabs, beams and girders may be considered restrained.” Conversely, because the restraint present in many construction systems cannot be determined so neatly, the IBC requires that these assemblies be considered unrestrained unless the registered design professional shows by the requisite analysis and details that the system qualifies for a restrained classification. Furthermore, the code requires that any construction assembly that is to be considered restrained be identified as such on the drawings.

703.3   Methods for determining fire resistance. In addition to those assemblies and materials considered fire-resistance-rated construction based on designs certified by an approved agency, a number of other methods for determining fire resistance are set forth in this section. Where it can be determined that the fire-resistance rating of a building element is in conformance with one of the six listed methods or procedures, such a rating is considered acceptable. The fire exposure and acceptance criteria of ASTM E 119 or UL 263 are the basis for applying all of the methods, enabling consistent and compliant application regardless of the method used.

703.4   Automatic sprinklers.   As a general rule, the fire-resistance ratings of building elements, components, and assemblies established through the code are to be determined in accordance with the test procedures set forth in ASTM E 119 or UL 263. Any of the methods for determining fire resistance listed in Section 703.3 are acceptable where such methods are based on the fire exposure and acceptance criteria specified in ASTM E 119 or UL 263. A fire suppression system is not permitted to be included as part of the tested element, component, or assembly in order to establish the fire-resistance rating. It has been generally accepted that the various fire-resistance ratings mandated throughout the code have been established based on an assumption that the fire assembly would pass the standardized tests without the assistance of water cooling during fire exposure. This provision clarifies the assumption.

It is important to note that these provisions are not intended to limit the use of Section 104.11 by building officials for the approval of alternative methods on a case-by-case basis. While the prescriptive provisions of the code are based on fire-resistance ratings established without the benefit of any automatic fire-suppression system, the building official has the authority to evaluate and approve alternative materials, designs, and methods of construction that meet the intent and purpose of the code.

703.5   Noncombustibility tests.   Throughout the IBC, particularly in Chapter 6, the terms combustible and noncombustible are used. Under many different conditions, limits are placed on the use of combustible building materials, particularly in buildings of Type I or II construction. This section sets forth the two methods for determining if a material is noncombustible.

For most materials, ASTM E 136 is the test standard used to determine if a material is noncombustible. Composite materials such as gypsum board are also considered noncombustible if they comply with the criteria of Section 703.5.2. Such materials must have a structural base of noncombustible materials with a surfacing limited in thickness and flame spread.

Note that the term noncombustible does not apply to surface finish materials.

703.6   Fire-resistance-rated glazing.   The use of fire-resistance-rated glazing typically only occurs where the limitations placed on fire-protection-rated glazing make it undesirable or impractical. Fire-resistance-rated glazing is subjected to the ASTM E 119 or UL 263 testing criteria, which include stringent limitations on temperature rise through the assembly. Because the glazing is regulated as a wall assembly rather than an opening protective, its use is not limited by any of the provisions of Section 716. It is only regulated under the appropriate code requirements for a fire-resistance-rated wall assembly.

The labeling requirements specific to fire-resistance-rated glazing are set forth in Table 716.3. The table indicates that glazing intended to meet the wall assembly criteria be identified with the marking “W-XXX.” The “W” indicates that the glazing meets the requirements of ASTM E 119 or UL 263, thus qualifying the glazing to be used as part of a wall assembly. It also indicates that the glazing meets the fire-resistance, hose-stream, and temperature-rise requirements of the test standard. The fire-resistance rating of the glazing will then follow the “W” designation.

703.7   Marking and identification.   The integrity of fire and/or smoke separation walls is subject to compromise during the life of a building. During maintenance and remodel activities, it is not uncommon for new openings and penetrations to be installed in a fire or smoke separation without the recognition that the integrity of the construction must be maintained or that some type of fire or smoke protective is required. The reduction or elimination of protection that occurs is typically not malicious. Rather, the installation of an inappropriate air opening, or the penetration of the separation without the proper firestopping, is often done due to the lack of information regarding the wall assembly’s function and required fire rating.

Through the identification of fire and smoke separation elements, it is possible for tradespeople, maintenance workers, and inspectors to recognize the required level of protection that must be maintained. The requirements apply to all wall assemblies where openings or penetrations are required to be protected. This would include exterior fire-resistance-rated walls as well as fire walls, fire barriers, fire partitions, smoke barriers, and smoke partitions. The identifying markings must be located within 15 feet (4,572 mm) of the ends of the wall and at maximum 30-foot intervals (9,144-mm) to increase the possibility that they would be visible during any work on the wall assemblies. A minimum letter height of 3 inches (76 mm) is also prescribed along with sample language for the marking. See Figure 703-6.

Figure 703-6   Identification sign for fire barrier.

It is intended that the identification marks be located in areas not visible to the general public. Specific locations set forth in the provisions indicate that the identification is to be provided within those concealed spaces that are accessible, such as above suspended ceilings and in attic areas.

Section 704 Fire-Resistance Rating of Structural Members

Structural frame members such as columns, beams, and girders are regulated for fire resistance based on a building’s type of construction. Some types of constructions mandate a higher level of fire endurance for structural members and assemblies on account of the critical nature of their function. Type of construction considerations is based primarily on the potential for building collapse when subjected to fire. Therefore, the structural frame is specifically addressed in Table 601 as to the required fire-resistance ratings. This section provides further details for the protection of structural members.

Figure 704-1 provides simple details of fire protection of structural members that indicate the principle of mass effect. Mass effect is beneficial to the protection requirements for structural members of a heavy cross section. In the case of steel members, the amount of protection depends on the weight of the structural steel member. A heavy, massive structural steel cross section behaves such that the heat applied to the surface during a fire is absorbed away from the surface, resulting in lower steel surface temperatures. Thus, the insulating thicknesses indicated by tests or in Table 721.1(1) should not be used for members with a smaller weight than that specified in the test or table.

Figure 704-1   Mass effect.

704.2   Column protection.   Primary structural frame members require fire-resistive protection in buildings of Type I, IIA, IIIA, and VA construction. Under all conditions, columns considered as a part of the primary structural frame system must be protected by individual encasement. This protection must occur on all sides of the column and extend for the column’s full height. Where a ceiling is provided, the fire resistance of the column is to be continuous from the top of the foundation or floor/ceiling assembly below through the ceiling space to the top of the column. The fire protection required for the column shall also be provided at the connections between the column and any beams or girders. Where the column is located within a fire-resistance-rated wall assembly as shown in Figure 704-2, the mandated column protection must still be provided through individual encasement. It is not acceptable to simply place an unprotected column within a fire-resistance-rated wall assembly and consider the column as fire-resistant rated.

Figure 704-2   Individual protection of structural columns.

704.3   Protection of the primary structural frame other than columns.   The code intends that the fire-resistive protection for primary structural frame members be applied to the individual structural member. This is based on the differences in both the testing procedure and the conditions of acceptance that were discussed in Section 703. In other words, the code does not intend that a primary structural frame member be protected by a wall assembly or fire-resistance-rated horizontal assembly, except as permitted by this section.

Under certain restrictions, the code allows the use of a floor/ceiling or roof/ceiling assembly to provide protection for structural members, rather than requiring that they be individually protected. The criteria for use of alternative membrane protection in lieu of individual encasement are depicted as follows:

1.   The use of the ceiling protection applies only to horizontal structural members, such as girders, trusses, beams, or lintels. (See Section 704.2 for column protection.)

2.   The structural members shall not support directly applied loads from more than two floors or one floor and roof, or support a load-bearing wall or a non-load-bearing wall more than two stories in height.

3.   The required fire-resistance rating of the assembly shall be at least equal to that required by the code for the individual protection of the structural members.

Examples of various conditions are shown in Figure 704-3.

Figure 704-3   Protection of primary structural frame members.

704.4   Protection of secondary members. Secondary members, as defined in Section 202, may be protected in the same manner as primary structural frame members where a fire-resistance rating is required. Such elements can be individually encased or protected by a membrane or ceiling of a horizontal assembly. Floor joists and roof joists are examples of secondary members that are permitted to be protected by the horizontal assembly in which they are located. In light-frame construction, membrane protection is also permitted for studs and similar elements that are integral elements in load-bearing walls.

704.5   Truss protection. It is the intent of the IBC that this provision be applied to trusses that are a part of the primary structural frame as defined in Section 202. In this case, the code permits the encapsulation with fire-resistive materials of the entire truss assembly. It is the intent of the code that the thickness and details of construction of the fire-resistive protection be based on the results of full-scale tests or of tests on truss components. Approved calculations based on such tests that show that the truss components provide the fire endurance required by the code are also acceptable. One application of this concept is in the use of the encapsulated trusses as dividing partitions between hotel rooms in multistory steel-frame buildings. Because the truss becomes part of the primary structural frame where it used to span between exterior wall columns, it provides a column-free interior. The fire-resistive design of the encapsulated protection can be based either on tests or on analogies derived from fire tests.

Additional criteria for the protection of primary structural members are illustrated in Figures 704-4 and 704-5, which depict details for attached metal members and reinforcing discussed in Sections 704.6 and 704.7. The provisions of Section 704.9 for impact protection are also illustrated in Figure 704-6.

Figure 704-4   Protection of structural steel column.

Figure 704-5   Reinforcing steel in concrete joists.

Figure 704-6   Impact protection.

704.10   Exterior structural members. The code provides that structural frame elements in the exterior wall or along the outer lines of a building must be protected based on the higher rating of three criteria. The minimum fire-resistance rating is determined by evaluating the requirements for (1) the structural frame per Table 601, (2) exterior bearing walls per Table 601, and (3) fire separation distance per Table 602. The highest of these three ratings is the minimum required rating of the structural members. See Application Example 704-1.

The intent of the provisions is that the structural frame should never have a lower fire rating than that required to protect the frame from internal fires. Nevertheless, if the exposure hazard from an external source is so great as to require exterior wall protection, a higher rating may be required.

704.11   Bottom flange protection.   Exempted from the requirements for fire protection in buildings of fire-resistance-rated construction are the bottom flanges of short-span lintels, and shelf angles or plates that are part of the structural frame. It is assumed by the code that the arching action of the masonry or concrete above the lintel will prevent anything more than just a localized failure. Furthermore, only the bottom flange is permitted to be unprotected and, as a result, the wall supported by the lintel will act as a heat sink to draw heat away from the lintel and thereby increase the length of time until failure that is due to heat. This latter rationale also applies to shelf angles and plates that are not considered a part of the structural frame. The limitation to spans no greater than 6 feet 4 inches (1,931 mm) is intended to allow such unprotected lintels and angles where a pair of 36-inch (914-mm) doors is installed in the opening.

Application Example 704-1

Section 705 Exterior Walls

Because of the potential for radiant heat exposure from one building to another, either on adjoining sites or on the same site, the IBC regulates the construction of exterior walls for fire resistance. Opening protection in such walls may also be required based on the fire separation distances involved. In addition to the regulation of exterior walls and openings in such walls, the code addresses associated projections, parapets, and joints.

705.2   Projections. Architectural considerations quite often call for projections from exterior walls such as cornices, eave overhangs, and balconies. Where these projections are from walls that are in close proximity to a lot line, they create problems that are due to trapping the convected heat from a fire in an adjacent building. As this trapped heat increases the hazard for the building under consideration, the code mandates a minimum distance the leading edge of the projecting element must be separated from the line used to determine fire separation distance. The permitted extent of projections is established by Table 705.2 and based solely on the clear distance between the building’s exterior wall and an interior lot line, centerline of a public way, or assumed imaginary line between two buildings on the same lot. Where the distance is less than 2 feet (609 mm), all types of projections are prohibited. As the clear distance increases to 2 feet (609 mm) and beyond, projections are permitted; however, the extent of such projections is regulated.

The reference to multiple buildings on the same lot is intended to address only those projections that extend beyond the opposing exterior walls of the adjacent buildings. For those exterior walls that directly oppose each other, the limits on projecting elements are not applicable where the two buildings are being considered as a single building under Exception 1 to Section 705.3. However, those projections that occur at exterior walls not located in opposition to those exterior walls of an adjacent building are to be regulated by the provisions of Section 705.2. The application of the exception to Section 705.2 is shown in Figure 705-1.

Figure 705-1   Two buildings regulated as a single building on the lot.

Projections from buildings are further regulated in order to prevent a fire hazard from inappropriate use of combustible materials attached to exterior walls. Thus, the IBC requires that projections from walls of Type I or II buildings be of noncombustible materials. However, it should be noted that certain combustible materials are permitted for balconies and similar projections as well as bay windows and oriel windows in accordance with Sections 1406.3 and 1406.4.

For buildings that the code considers to be of combustible construction (Type III, IV, or V construction), both combustible and noncombustible materials are permitted in the construction of projections. Where combustible projections are used and they extend into an area directly adjacent to an adjoining lot, the code requires that they be of at least 1-hour fire-resistance-rated construction, of heavy-timber construction, constructed of fire-retardant-treated wood, or as required in Section 1406.3 for balconies and similar projections. This requirement is based on a potential for a severe exposure hazard and, consequently, the code intends that combustible materials be protected or, alternatively, be of heavy-timber construction, which has comparable performance when exposed to fire. An example is shown in Figure 705-2.

Figure 705-2   Protection of combustible projections.

The criteria require that combustible projections be of 1-hour construction, Type IV construction, or fire-retardant-treated wood, or alternatively comply with Section 1406.3, where the projection extends within a distance of 5 feet (1,524 mm) to the line where fire separation distance is measured (interior lot line, centerline of a public way, or assumed imaginary line between two buildings on the same lot).

Because projections are typically regulated independent of the roof construction, it is entirely possible that their construction types may be inconsistent. For example, Figure 705-3 shows two situations where the roof construction and resulting projections may differ in their required protection. Figure A relates a Type VA building with a 1-hour fire-resistance-rated roof system but a nonrated projection. On the other hand, Figure B indicates a Type VB building with nonrated roof construction but a minimum 1-hour-protected projection. In each case, the roof construction and its projection are regulated differently because of the concept of fire resistance being applied.

Figure 705-3   Projection versus roof protection.

705.3   Buildings on the same lot. The IBC regulates exterior wall construction, opening protection, and projection extent and protection based on the proximity of the exterior walls to lot lines, either real or assumed. This section provides the code requirements for the establishment of imaginary lines between buildings on the same lot. Where two or more buildings are to be erected on the same site, the determination of the code requirements for protection of the exterior walls is based on placing an assumed imaginary line between buildings. Figure 705-4 illustrates an example of two nonsprinklered Type IIIB buildings housing Group S-2 occupancies sharing a 30-foot-wide (9,144-mm) yard, and it is noted that the imaginary line can be located anywhere between the two buildings so that the best advantage can be taken of wall and opening protection, depending on the use and architectural considerations for the exterior walls of the buildings. For example, if unprotected openings amounting to 25 percent of the area of the exterior walls of each nonsprinklered building were desired, the imaginary line would be located so that the distance between it and each building would permit such an amount of unprotected openings. Thus, the code would require that each building be placed at least 15 feet (4,572 mm) from the imaginary line in order to have unprotected openings totaling 25 percent of each opposing wall area. If one of the buildings were to have no openings in the exterior wall, the imaginary line could be placed at the exterior wall of the building without openings. The other building would be located at a distance of 30 feet (9,144 mm) or more from the imaginary line and the other building. In the first case described, the opposing nonbearing exterior walls would both be required to be of minimum 1-hour fire-resistance-rated construction as they are each located less than 30 feet (9,144 mm) from the imaginary line. However, the wall located 30 feet (9,144 mm) from the imaginary line would not require any fire rating. Also, in the last example, Section 705.11 could possibly require that the exterior wall on the assumed lot line be provided with a parapet. See discussion of Section 705.11.

Figure 705-4   Buildings on the same lot.

In the case where a new building is to be erected on the same lot as an existing building, the same rationale applies as depicted in Figure 705-4, except that the exterior wall, opening, and projection protection of the existing building determine the location of the assumed imaginary line. As shown in Figure 705-5, the exterior wall and opening protection of the existing building must remain in compliance with the provisions of the IBC.

Figure 705-5   Buildings on the same lot.

As an alternative, where two or more buildings are located on the same lot, they may be considered to be a single building subject to specified limitations. For further discussion of this condition, see the commentary on Section 503.1.2.

705.5   Fire-resistance ratings.   The IBC requires that exterior walls conform to the required fire-resistance ratings of Tables 601 and 602. Bearing walls must comply with the more restrictive requirements of both tables, whereas nonbearing exterior walls need only comply with Table 602. Table 601 is intended to address the fire endurance of bearing walls necessary to prevent building collapse that is due to fire for a designated time period. Table 602 is used to determine the required fire-resistance ratings that are due to exterior fire exposure from adjacent buildings, as well as the interior fire exposure that adjacent buildings are exposed to on account of the uses sheltered by the exterior walls. Where structural frame members are located within exterior walls, reference to Section 704.10 is required. Examples of the use of these provisions are shown in Application Examples 601-1 and 704-1.

Section 703.2.1 addresses nonsymmetrical interior wall construction, whereas this section of the code addresses nonsymmetrical construction for exterior walls. This method of construction, which provides for a different membrane on each side of the supporting elements, is much more typical for exterior applications. As an example, a nonsymmetrical exterior wall may consist of wood studs covered with gypsum board on the inside, with sheathing and siding on the exterior side. See Figure 705-6. Where exterior walls have a fire separation distance of more than 10 feet (3,048 mm), the fire-resistance rating is allowed to be determined based only on interior fire exposure. This recognizes the reduced risk that is due to the setback from the lot line. For fire separation distances greater than 10 feet (3,048 mm), the hazard is considered to be predominantly from inside the building. See Figure 705-7. Thus, fire-resistance-rated construction whose tests are limited to interior fire exposure is considered sufficient evidence of adequate fire resistance under these circumstances. However, at a distance of 10 feet (3,048 mm) or less, there is the additional hazard of direct fire exposure from a building on the adjacent lot and the possibility that it may lead to self-ignition at the exterior face of the exposed building. Therefore, exterior walls located very close to any lot line must be rated for exposure to fire from both sides. The listings of various fire-resistance-rated exterior walls will indicate if they were only tested for exposure from the inside, usually by a designation of “FIRE SIDE” or similar terminology. Where so listed, their use is limited to those applications where the wall need only be rated from the interior side. It should be noted that this allowance is applicable regardless of why the wall requires a rating. Using a Type VA building as an example, those exterior bearing walls required by Table 601 to be minimum 1-hour walls need only be rated for exposure to fire from the interior side if they are located such that the fire separation distance is more than 10 feet (3,048 mm).

Figure 705-6   Nonsymmetrical exterior wall construction.

Figure 705-7   Nonsymmetrical exterior wall ratings.

705.6   Structural stability. This section refers the code user to Section 705.11 for parapets in determining the required height of exterior walls. It also addresses the two conditions regarding elements used to brace the exterior wall. Where such elements are located within the plane of the wall (as part of the wall assembly) or on the outside of the wall, the bracing members are to be regulated for both external fire exposure and internal fire exposure based on the references to Tables 601 and 602. Those bracing elements that occur within the building, such as floor joists and/or roof joists that frame into the exterior wall, are also required to be protected from internal fire exposure if mandated by Table 601. However, external fire exposure concerns addressed in Table 602 are not specifically addressed. Floor systems, roof systems, and other elements that provide lateral bracing from the interior side of an exterior wall are only required to be fire-resistance rated when required by Table 601.

705.7   Unexposed surface temperature.   The provisions of this section provide a reduction of the prescriptive fire-resistance requirements for exterior walls under certain conditions. A fire-resistance-rated wall is generally required to meet the conditions of acceptance of ASTM E 119 or UL 263 for fire endurance and hose-stream tests on the surface exposed to the test fire, and heat-transmission limits on the unexposed surface. At fire separation distances beyond the point where no openings are allowed, typically 3 feet (914 mm), two more options are available:

1.   Where opening protection is required, but the percentage of opening protection is not limited [typically a fire-separation distance of more than 20 feet (6,096 mm)], compliance with the heat-transmission limits of ASTM E 119 or UL 263 is not required. This recognizes that, although heat transmission is an important consideration for interior walls, the fire hazard that the limit addresses is substantially reduced once the exterior wall of a building is set back far enough that the fire hazard it presents to (and receives from) a building on an adjacent lot does not warrant a limit on the percentage of opening protection to limit the hazard. It has the effect of compliance with the conditions of acceptance for fire assemblies of the same hourly rating.

According to NFPA 252 for fire door assemblies and NFPA 257 for fire window assemblies, nearly identical conditions of acceptance for fire endurance and hose-stream tests are required, but not limits on heat transmission. Because an unlimited percentage of opening protection is allowed, the lack of a heat transmission limit for exterior walls is consistent with that for fire door and fire window assemblies. An exterior wall that does not meet the heat transmission limits is considered equivalent to an opening protective of the same hourly rating in its reduced ability to limit heat transmission.

2.   Where the percentage of opening protection is limited [typically having a fire separation distance between 3 feet (914 mm) and 20 feet (6,096 mm)], a similar reduction is possible, provided a correction is made according to the formula presented in this section. The formula converts the actual proposed area of protected openings to an increased equivalent area in proportion to the area of exterior wall surface under consideration that lacks adequate control of heat transmission. It places additional limits on the allowable percentage of opening protection.

The formula increases the required percentage of opening protection, whereas Section 705.8 sets limits on the percentage. Relative to the limitations of Section 705.8, this method allows for a smaller percentage of opening protection at the same fire separation distance. Thus, a greater fire separation distance is required to maintain the same percentage of opening protection. The reduction of the heat transmission capacity of the exterior walls is compensated by a reduction in the allowable percentage of opening protection. Without this provision, a fire-resistance-rated exterior wall that does not meet the heat transmission limits would not be allowed.

If actual test results or other substantiating data are available, they may be used in the computations. In their absence, the standard time-temperature curve of ASTM E 119 and UL 263 would be used, which results in an equivalent area of protected openings equal to the actual area of protected openings plus the exterior wall area without adequate control of heat transmission per ASTM E 119 and UL 263. This is converted into a percentage of opening protection and compared to the limits of Section 705.8. The use of actual test results may reduce this effect. See Section 705.8 for the basic limits prior to modification by this provision.

705.8.1   Allowable area of openings.   Openings in an exterior wall typically consist of windows and doors. Occasionally, air openings such as vents are also present. The maximum area of either protected or unprotected openings permitted in each story of an exterior wall is regulated by this section. In addition, both unprotected and protected openings are permitted in the same exterior wall based on a unity formula. The term protected in this section refers to those elements such as fire doors, fire windows, and fire shutters regulated in Section 716. Protected openings have the mandated fire-protection rating necessary to perform their function. Unprotected openings are simply those exterior openings that do not qualify as protected openings. Opening protection presents a higher fire risk than fire-resistance-rated construction insofar as it does not meet the heat transmission limits of ASTM E 119 or UL 263, as previously discussed. At increasing distances from where openings are no longer prohibited, the hazard from heat radiation decreases, allowing the percentage of openings, both protected and unprotected, to increase. The high hazard of heat exposure at small fire separation distances justifies the prohibition of openings in order to limit the percentage of wall area without adequate heat transmission limits. As the fire separation distance increases, the percentage of openings is allowed to increase in compensation. At greater distances, the limit on the percentage of opening protection is eliminated. This recognizes that, at greater distances, the lack of adequate control of heat transmission does not pose a significant hazard to adjacent buildings, but containment of the fire to its origin inside the exposed building is still important.

There is a distance from lot lines where the hazard is reduced to such a degree that all opening limitations are no longer warranted. At this point, exposure to and from adjacent buildings is not significant and the need for fire resistance at exterior walls is reduced to fire protection of bearing walls and structural members in order to delay building collapse in the event of fire. Arguably the most important provision is Exception 2 to Section 705.8.1. It indicates that if the exterior wall of the building and its primary exterior structural frame are not required by the code to have a fire-resistance rating, then unlimited unprotected openings are permitted. In other words, if the wall does not require a rating, any openings in the wall are unregulated for area and fire protection. An example is shown in Figure 705-8.

Figure 705-8   Unlimited unprotected openings.

Although not stated in the exception, only when Table 602 requires a fire-resistance rating does Table 705.8 limit the maximum area of exterior openings. Where some other provision of the code mandates a fire-resistance-rated exterior wall, such as an exterior bearing wall supporting a fire-resistance-rated horizontal assembly, the limitations of Table 705.8 do not apply. It is also not necessary to review Table 601 to apply the exception as the conditions are established in such a manner that Table 602 provides all of the necessary information. Directly stated, if Table 602 does not mandate a fire-resistance-rated exterior wall, an unlimited amount of unprotected openings are permitted.

The limitation on exterior openings is also not applicable for first-story openings in buildings of other than Group H as indicated in Exception 1 to Section 705.8. Limited in application, this exception allows an unlimited amount of unprotected openings at the first story under specified circumstances. Applicable only to those buildings that require a fire-resistance-rated exterior wall where the fire separation distance equals or exceeds 10 feet (3,048 mm), the provisions are often used for opposing buildings having storefront systems. See Figure 705-9.

Figure 705-9   Unlimited openings in the first story exterior wall.

How are exterior openings regulated in fully sprinklered buildings? Table 705.8 also recognizes an increase in the allowable area of unprotected exterior openings for those buildings that are provided with an automatic sprinkler system throughout. For example, the fire-resistance-rated exterior wall of a fully sprinklered building having a fire separation distance of 15 feet (4,572 mm) may have 75 percent of its surface area consisting of unprotected openings. If the building is not sprinklered, the limit on unprotected openings is only 25 percent. In other than higher-level Group H occupancies, the maximum permitted area of unprotected openings in an exterior wall is allowed to be the same as the tabulated limitations for protected openings, provided the building is protected throughout with an NFPA 13 automatic sprinkler system. The increased areas permitted due to sprinkler protection are all incorporated directly into Table 705.8. It is important to note that the presence of an automatic sprinkler system does not increase the maximum allowable opening area for protected openings. Whereas the benefits of such an increase would seem justifiable because of the increased level of protection, such an allowance is not addressed in the code. In addition, the unity formula (Equation 7-2) is not applicable to fully sprinklered buildings insofar as the code provides an increased allowance for unprotected openings to the amount permitted for protected openings.

705.8.2   Protected openings.   Section 716.6 is referenced for identifying the level of protection required for windows needing opening protection. It further references Section 716.5 for fire doors and fire shutters. The use of sprinklers and water curtains to eliminate the required opening protection is addressed in the exception. It indicates that where the building is sprinklered throughout, those openings protected by an approved water curtain do not need to be fire-protective assemblies. However, the exception has virtually no application when the provisions of Table 705.8 are implemented, as the table allows for the elimination of protected openings in sprinklered buildings without the need for water curtains. There are a number of provisions throughout the IBC where the exception could be used. For example, Section 1028.4.2 typically mandates ¾-hour fire-protected openings in walls of egress courts less than 10 feet (3,048 mm) in width. In a fully sprinklered building, the use of a complying water curtain would eliminate the need for such openings to have a fire-protection rating. Other provisions where the exception might be applied include Section 1009.7.2 for exterior areas for assisted rescue and Section 1023.7 for interior exit stairways and ramps.

705.8.4   Mixed openings.   Table 705.8 specifies the maximum allowable percentage of protected and unprotected openings, considered separately and based on fire separation distance alone. The unity formula (Equation 7-2) as set forth in Section 705.8.4 determines the maximum allowable area of protected and unprotected openings where they are proposed together in an exterior wall at an individual story of a nonsprinklered building. It offers a traditional interaction relationship, namely, the sum of the actual divided by the sum of the allowable cannot exceed one. An example of the determination of the maximum area of exterior wall openings, where both protected and unprotected openings are used, is provided in Application Example 705-1. The use of this table is limited to those buildings that are not provided with an NFPA sprinkler system throughout. Where the building is fully sprinklered, the code provides no advantage where protected openings are provided.

Application Example 705-1

705.8.5   Vertical separation of openings. The intent of this section is to limit the vertical spread of fire from floor to floor at the exterior wall of the building. The code requires exterior flame barriers projecting out either from the wall or in line with the wall. These flame barriers are intended to prevent the leap-frogging effect of a fire at the outside of a building. See Figure 705-10. However, there are three exceptions that eliminate the required barriers. The first is for buildings three stories or less in height. The second is for fully sprinklered buildings. The third exception is for open parking garages. It is probable that this provision will have very limited application, as it is doubtful there will be much new construction of four stories or more without sprinkler protection. Provisions addressing the spread of fire from floor to floor on the interior side of an exterior wall, such as at the intersection of a floor and curtain wall system, are found in Section 715.4.

Figure 705-10   Flame barriers.

705.8.6   Vertical exposure.   The scope of this section is limited to buildings located on the same lot and to the issue of the protection of openings in the exterior wall of a higher building above the roof of a lower building. It requires each opening in the exterior wall that is less than 15 feet (4,572 mm) above the roof of the lower building to be protected if the horizontal fire separation distance of the opening in the exterior wall of the higher building is less than 15 feet (4,572 mm) from the exterior wall of the lower building. See Figure 705-11. There is an exception that applies where the roof construction has at least a 1-hour fire-resistance rating, also illustrated in Figure 705-11. Application of this provision potentially mandates a higher level of protection than that required by the code for two buildings on separate adjoining lots. The presence of a lot line between two buildings institutes the concept of fire separation distance in the regulation of the opposing exterior walls and any openings in such walls. On a single lot with two buildings, the same concept is applied owing to the requirement for the placement of an assumed imaginary line between the buildings. This line is also the basis for regulating exterior wall and opening protection that is due to fire separation distance. The provisions of Section 705.8.6 introduce additional requirements that may not be mandated on account of the fire separation distance concept. In addition, where two buildings are located on the same lot, the provisions of Sections 705.3 and 503.1.2 permit them to be considered a single building if the aggregate area of the buildings is within the limits of Chapter 5 for a single building. For consistent application of the fire separation distance concept, it would appear that the methodology for buildings on the same lot could be permitted to be used rather than the vertical exposure provisions of Section 705.8.6.

Figure 705-11   Vertical exposure.

It appears that the provision is intended to mirror the termination requirements and allowances for fire walls where located in stepped buildings as established in Section 706.6.1. It would be logical to assume that if a fire wall is not necessary to obtain code compliance, resulting in no required application of the fire wall termination requirements, the same concept should be considered when applying this provision to buildings on the same lot that can be regulated as a single building.

705.11   Parapets.   This section intends that the exterior walls of buildings shall extend a minimum of 30 inches (762 mm) above the roof to form a parapet. There are two reasons for the parapet:

1.   To prevent the spread of fire from the roof of the subject building to a nearby adjacent building.

2.   To protect the roof of a building from exposure that is due to a fire in an adjacent nearby building.

Most buildings do not have complying parapets, and those that do typically use them to hide the roof slope or roof-top equipment. Therefore, the exceptions to this section tend to become the general rule. Three of the six exceptions listed in the code—1, 3, and 6—involve cases where the parapet would serve no useful purpose. In Exception 2, a concession is made to the small-floor-area building, and in Exceptions 4 and 5, an alternative method for providing equivalent protection is delineated. It is not necessary that all of the exceptions listed apply. Compliance with only one of the exceptions is all that is necessary for the elimination of a complying parapet.

Certainly, walls not required to be of fire-resistance-rated construction would not benefit from a parapet. In the case of walls that terminate at 2-hour fire-resistance-rated roofs or roofs constructed entirely of noncombustible materials, the parapet would be of little benefit, as the construction of the roof would prevent the spread of fire from or into the building. The exception for noncombustible roof construction is not intended to preclude the use of a classified roof covering.

In the case of walls permitted to have unprotected openings in conformance with Exception 6, the code assumes that the exterior wall will be far enough away from either an exposing building or an exposed building so that the protection provided by the parapet will not be necessary. This distance will vary based on the presence of a sprinkler system in the building, as shown in Figure 705-12.

Figure 705-12   Parapet exception.

The fourth exception makes a provision for 1-hour fire-resistance-rated exterior walls that are constructed similar to 2-hour fire walls that terminate at the underside of the roof sheathing, deck, or slab. This provides designers with an alternative to the use of parapets while recognizing that these walls provide adequate protection of the structure and its occupants as well as consistency with Section 706.6 for fire walls. See Figure 705-13. Exception 5 applies only to Group R-2 and R-3 occupancies and is intended to protect at the roof line through the use of a noncombustible roof deck, fire-retardant-wood sheathing, or a gypsum-board underlayment.

Figure 705-13   Parapet alternative.

705.11.1   Parapet construction.   In addition to having the same degree of fire resistance as required for the wall, the code also requires that the surface of the parapet that faces the roof be of noncombustible materials for the upper 18 inches (457 mm). Thus, a fire that might be traveling along the roof and reaching the parapet will not be able to continue upward along the face of the parapet and over the top and expose a nearby adjacent building. The requirement only applies to the upper 18 inches (457 mm) of the parapet to allow for extending the roof covering up the base of the parapet so that it can be effectively flashed. The 18-inch (457-mm) figure is based on a parapet height of at least 30 inches (762 mm).

As stated in the code, the 30-inch (762-mm) requirement is measured from the point where the roof surface and wall intersect. Therefore, when a cricket is installed adjacent to the parapet, the 30-inch (762-mm) dimension would be taken from the top of the cricket.

In those cases where the roof slopes upward away from the parapet and slopes greater than 2 units vertical in 12 units horizontal (16.7-percent slope), the parapet is required to extend to the same height as any portion of the roof that is within the distance where protection of openings in the exterior wall would be required. However, in no case shall the height of the parapet be less than 30 inches (762 mm). See Figure 705-14 for an illustration of this requirement.

Figure 705-14   Parapet requirements.

Section 706 Fire Walls

The IBC permits fire walls to be installed within a building, thereby creating one or more smaller-area buildings. It further intends that each portion of the structure so separated may be considered a separate building for all purposes of the code. The concept is based on buildings on adjoining lots having a common party wall or two separate fire-resistance-rated walls located on the lot line. The high level of fire-resistance-rated construction between the two buildings, along with other controls, is deemed adequate for the protection of one building from its neighboring building. The use of one or more fire walls within a building is optional, based on a decision by the designer. The code never mandates a fire wall be used, but rather offers it as an alternative to other mandated provisions. There are various reasons for using fire walls within buildings; however, there are three such reasons that are quite common:

1.   Allowable building area. The installation of one or more fire walls reduces the floor area in each of the separated buildings. Smaller floor areas can result in a reduction in the type of construction for one or more of the smaller buildings.

2.   Multiple construction types. By separating a structure into separate buildings, they each are regulated independently for type of construction. Thus, not all of the structure would need to be classified based on the lowest construction type involved.

3.   Automatic sprinkler systems. Fire walls can be used to reduce building size for the purpose of eliminating a requirement for the installation of an automatic sprinkler system.

Examples of these various uses of fire walls are shown in Application Examples 706-1 through 706-3. A fourth application of the fire wall concept is found in Appendix B of the International Fire Code® (IFC®) relating to fire-flow requirements for buildings. Where structures are separated by fire walls without openings, the divided portions may be considered separate fire-flow calculation areas. There are numerous other applications for fire walls, all based on the concept of reducing hazards in buildings of a smaller size.

Application Example 706-1

Application Example 706-2

Application Example 706-3

706.1   General.   As previously mentioned, one or more fire walls may be constructed in a manner such that the code considers the portions separated by the fire walls to be separate buildings. Because a fire wall is such a critical element in the prevention of the spread of fire from one separated building to another, it is of great importance that the wall be situated and constructed properly. It must provide a complete separation. It should be noted that when a wall serves both as a fire barrier separating occupancies and a fire wall, the most restrictive requirements of each separation shall apply. The code also prohibits any openings in fire walls that are constructed on lot lines (defined as party walls).

706.1.1   Party walls.   A common wall located on the lot line between two adjacent buildings is considered a party wall under this provision of the code. Regulated as a fire wall in accordance with the provisions of Section 706, a party wall can be considered in lieu of separate and distinct exterior walls adjacent to the lot line. The hazard created by neighboring buildings adjacent to each other is further addressed through the requirement that no openings be permitted in a party wall. For purposes of this section, and consistent with the general provisions of Section 503.1 for structures containing fire walls, separate buildings are created.

706.2   Structural stability.   The objective of a fire wall is that a complete burnout can occur on one side of the wall without any effects of the fire being felt on the opposite side. Furthermore, the only damage to the wall will be the effects of fire and the shock of hose-stream application on the fire side. The code is very clear that fire walls should remain in place for the expected time period. Therefore, structural failure on either side of the wall shall not cause the collapse of the wall, nor can the required fire-resistance rating be diminished. In addition, structural members (especially members that conduct heat) that penetrate fire walls could limit their effectiveness and do not comply with this provision. Any structural member that passes through a fire wall could also adversely affect the integrity of the required fire-resistance-rated construction.

The intent of this section can be partially traced back to Section 101.3, which states that one of the goals of the code is to provide safety to fire fighters and emergency responders during emergency operations. During a fire, a fire wall provides a safe haven on the nonfire side for fire fighters to stage and fight a fire. It is critical that the fire wall does not pose a threat of collapse to the fire department personnel. This is more easily achieved where the fire wall is a nonbearing wall and is not penetrated by load-bearing elements. However, where a fire wall is proposed as a bearing wall, the building official should ensure that those structural members that frame into the wall will not cause the premature collapse of the fire wall prior to the hourly rating established for the wall. The structural engineer of record should provide evidence to this fact. If all structural elements framing into the fire wall, as well as their supporting members, have the same fire-resistance rating as the fire wall, it is reasonable to assume that the intent of the provision has been met.

As an option to a single fire wall, the code permits the use of a double fire wall if designed and constructed in accordance with NFPA 221. Double fire walls are simply two back-to-back walls, each having an established fire-resistance rating. While acceptable for use in a new structure, double fire walls are most advantageous where an addition is being constructed adjacent to an existing building and the intent is to regulate the addition as a separate building under the fire wall provisions. The exterior wall of the existing building, if compliant, can be used as one wall of the double wall system, with the new wall of the addition providing the second wall.

Double fire wall assemblies are to comply with the applicable provisions of NFPA 221, Standard for High Challenge Fire Walls, Fire Walls, and Fire Barrier Walls. This standard addresses a number of criteria for double fire walls, including fire-resistance rating, connections, and structural support. In order to meet the minimum fire-resistance rating for a fire wall as set forth in IBC Table 706.4, each individual wall of a double fire wall assembly is permitted to be reduced to 1 hour less than the minimum required rating for a single fire wall. For example, where IBC Table 706.4 requires the use of a minimum 3-hour fire wall, two minimum 2-hour fire-resistance-rated (double) fire walls are required. Similarly, two 3-hour fire walls in a double wall system can be considered as a single 4-hour fire wall, and two 1-hour fire walls used as a double wall qualify as a single 2-hour fire wall.

Since the intended goal of fire wall construction is to allow collapse of a building on either side of the fire wall while maintaining an acceptable level of fire separation, the only connection permitted by NFPA 221 between the two walls that make up the double fire wall is the flashing, if provided. Illustrated in the explanatory material to the standard, the choice of flashing methods must provide for separate flashing sections in order to maintain a complete physical separation between the walls. Each individual wall of the double wall assembly must be supported laterally without any assistance from the adjoining building. In addition, a minimum clear space between the two walls is recommended by NFPA 221 in order to allow for thermal expansion between unprotected structural framework, where applicable, and the wall assemblies that make up the double fire wall.

NFPA 221 can also be used as the design standard for the construction of other types of fire walls. Two other high challenge (HC) fire walls are addressed in NFPA 221, cantilevered HC fire walls and tied HC fire walls. Cantilever HC fire walls must be fully self-supported and nonbearing, with no connections to the buildings on either side other than flashing. Tied HC fire walls are limited to one-story conditions and supported laterally by the building framework with flexible anchors. Centered on a single column line or between a double column line, a tied HC fire wall shall be constructed such that the framework on each side of the wall shall be continuous or tied together through the wall.

706.3   Materials.   In buildings of other than Type V construction, fire walls shall be constructed of noncombustible materials. The high degree of protection expected from a fire wall mandates that noncombustible construction be used for all but the lowest type of construction.

706.4   Fire-resistance rating.   It is obvious that a fire wall performs the very important function of acting as a barrier to fire spread so that a fire on one side of the wall will not be transmitted to the other. On this basis, the fire wall must have a fire-resistance rating commensurate with the occupancy and type of construction of which it is constructed. The IBC provides that fire walls be of either 2-hour, 3-hour, or 4-hour fire-resistance-rated construction as specified in Table 706.4. Where the type of construction and/or occupancy group that occurs on one side of a fire wall is inconsistent with that on the other side, the more restrictive fire-resistance rating set forth in Table 706.4 shall apply. See Figure 706-1. Permitted openings in fire walls are addressed in Section 706.8.

Figure 706-1   Fire-resistance rating.

706.5   Horizontal continuity. A fire wall must not only separate the interior portions of the building but must also extend at least 18 inches (457 mm) beyond the exterior surfaces of exterior walls. See Figure 706-2. A number of exceptions permit the fire wall to terminate at the interior surface of the exterior finish material, with Exception 1 illustrated in Figure 706-3. Where combustible sheathing or siding materials are used, the wall must be protected for at least 4 feet (1,220 mm) on both sides of the fire wall by minimum 1-hour construction with any openings protected at least 45 minutes. If the sheathing, siding, or other finish material is noncombustible, such noncombustible materials shall extend at least 4 feet (1,220 mm) on both sides of the fire wall; however, unlike the previous exception, no opening protection is required. As an option, where the separate buildings created by the fire wall are sprinklered, the fire wall may simply terminate at the interior surface of noncombustible exterior sheathing.

Figure 706-2   Horizontal continuity.

Figure 706-3   Horizontal continuity.

706.5.1   Exterior walls. Where a fire wall creating separate buildings intersects with the exterior wall, there is the potential for direct fire exposure between the buildings at the exterior. Unless the intersection of the exterior wall and the fire wall forms an angle of at least 180 degrees (3.14 rad), such as a straight exterior wall with no offsets, a condition occurs similar to that of two buildings located on the same site. The proximity of the two buildings may be such that the distance between them would allow for direct fire or substantial radiant heat to be transferred from one building to the other. This condition is also possible where the two buildings on the lot are portions of a larger structure with fire wall separations.

Where the fire wall intersects the exterior wall to form an angle of less than 180 degrees (3.14 rad), the exterior wall for at least 4 feet (1,220 mm) on both sides of the fire wall shall be of minimum 1-hour fire-resistance-rated construction, and all openings within the 4-foot (1,220-mm) portions of the exterior wall are to be protected with 45-minute fire assemblies. See Figure 706-4. As an option, an imaginary lot line may be assumed between the two buildings created by the fire wall and the exterior wall, and opening protection would be based on the fire separation distances to the imaginary lot line. This method is consistent with the provisions of Section 705.3 for addressing two buildings on the same lot. An example is shown in Figure 706-5.

Figure 706-4   Fire wall intersection with exterior walls.

Figure 706-5   Imaginary lot line at extension of fire wall.

706.5.2   Horizontal projecting elements. Under the conditions where a horizontal projecting element such as a roof overhang or balcony is located within 4 feet (1,220 mm) of a fire wall, the wall must extend to the outer edge of the projection. This general requirement provides for a complete separation by totally isolating all building elements, including projections, on either side of a fire-resistance-rated wall. However, such a condition is typically not visually pleasing. Therefore, the code indicates the fire wall is not required to extend to the leading edge of the projecting element if constructed in compliance with one of three exceptions. The protection must extend through the projecting element unless the projection has no concealed spaces. Where the projecting element is combustible and has concealed spaces, the fire wall shall extend through the concealed area, whereas in noncombustible construction, the extension need only be 1-hour fire-resistance-rated construction. Under all of the exceptions, the exterior wall behind and below the projecting element is to be of 1-hour fire-resistance-rated construction for a distance not less than the depth of the projecting element on both sides of the wall. All openings within the rated exterior wall are to be protected by fire assemblies having a minimum fire-protection rating of 45 minutes. Figure 706-6 depicts these various conditions addressed in the exceptions.

Figure 706-6   Horizontal projecting elements.

706.6   Vertical continuity.   Having established the intent of the IBC that fire walls prevent the spread of fire around or through the wall to the other side, the IBC further ensures the separate building concept by specifying that the wall shall extend continuously from the foundation to (and through) the roof to a point 30 inches (762 mm) or more above the roof. The 30-inch (762-mm) parapet prevents the spread of fire along the roof surface from the fire side to the other side of the wall.

Several exceptions, some of which are illustrated in Figure 706-7, allow the fire wall to terminate at the underside of the roof sheathing, deck, or slab, rather than terminate in a parapet. The basis for such exceptions includes:

Figure 706-7   Termination of fire walls.

1.   Equivalent protection being provided by an alternative construction method;

2.   Aesthetic considerations, as parapets disrupt the appearance of the roof; or

3.   A combination of the two previous reasons.

It is emphasized that the term fire wall also limits its use to vertical walls. Therefore, there can be no horizontal offsets nor can the plan view of the wall change from level to level. See Figure 706-8.

Figure 706-8   Fire wall vertical community.

706.6.1   Stepped buildings.   Quite often, a fire wall is provided at a point in the building where the roof changes height. Under such conditions, the fire wall must extend above the lower roof for a minimum height of 30 inches (762 mm). In addition, the exterior wall shall be of at least 1-hour fire-resistance-rated construction for a total height of 15 feet (4,572 mm) above the lower roof. The exterior wall shall be of fire-resistance-rated construction from both sides. Any opening that is located in the lower 30 inches (762 mm) of the wall shall be regulated based on the rating of the fire wall. Openings above the 30-inch (762-mm) height, but not located above a height of 15 feet (4,572 mm), shall have a minimum fire-protection rating of 45 minutes. An illustration of this provision is depicted in Figure 706-9.

Figure 706-9   Stepped buildings.

An alternative is described in the exception that allows the fire wall to terminate at the underside of the roof sheathing, deck, or slab of the lower roof. It is very similar to Exception 2 in Section 706.6. Because the greatest exposure occurs from a fire penetrating the lower roof and exposing the adjacent exterior portion of the fire wall, the code mandates that all protection be applied to the roof assembly of the lower roof. As shown in Figure 706-10, the lower roof assembly within 10 feet (3,048 mm) of the wall shall be of minimum 1-hour fire-resistance-rated construction. In addition, no openings are permitted in the lower roof within 10 feet (3,048 mm) of the fire wall.

Figure 706-10   Stepped buildings.

Section 707 Fire Barriers

A common function of a fire barrier is to totally isolate one portion of a floor level from another through the use of fire-resistance-rated walls and opening protectives. Fire-resistance-rated horizontal assemblies are also often used in conjunction with fire barriers in multistory buildings in order to isolate areas vertically. This section identifies the different uses for fire barriers, as well as the method in which fire barriers are to be constructed.

707.3   Fire-resistance rating.   A fire barrier shall be used to provide the necessary separation for the following building elements or conditions:

1.   Shaft enclosure. The minimum required degree of fire-resistance for fire barriers used to create a shaft enclosure is based primarily on the number of stories connected by the enclosure. A minimum 2-hour fire-resistance rating is mandated where four or more stories are connected, with only a 1-hour rating required where connecting only two or three stories. In all cases, the rating of the fire barriers creating a shaft enclosure must equal or exceed that of the floor assembly that is penetrated by the enclosure.

2.   Interior exit stairway construction. The separation between an interior exit stairway (stair enclosure) and the remainder of the building shall be accomplished with fire barriers having either a 1- or 2-hour fire-resistance rating, as required by Section 1023.2. Similar enclosures are required for interior exit ramps.

3.   Exit access stairway enclosures. Where exit access stairways are required to be enclosed by Section 1019.3, the enclosure shall include the use of fire barriers.

4.   Exit passageway. An exit passageway must be isolated from the remainder of the building by minimum 1-hour fire-resistance-rated fire-barrier walls. Where horizontal enclosure is also required, minimum 1-hour fire-resistance-rated horizontal assemblies must also be used to totally isolate the exit passageway. Where an exit passageway is a continuation of an interior exit stairway, it must, at a minimum, maintain the fire-resistance rating of the stairway enclosure.

5.   Horizontal exit. A minimum 2-hour fire-resistance-rated fire barrier may be used to create a horizontal exit when in compliance with all of the other provisions of Section 1026. The fire barrier creates protected compartments where occupants of the building can travel to escape the fire incident.

6.   Atrium. Unless a complying glazing system or ¾-hour glass block construction is used, minimum 1-hour fire barriers are required when isolating an atrium from surrounding spaces.

7.   Incidental uses. Table 509 indicates the required separation or protection required for special hazard areas such as waste and linen collection rooms, laboratories, and furnace rooms. Where a 1- or 2-hour fire-resistance-rated wall is required, it shall be a fire barrier.

8.   Control areas. Table 414.2.4 identifies the minimum required fire-resistance rating for fire barriers used to create control areas in buildings housing hazardous materials. A minimum rating of 1 hour is mandated for separating control areas located on the first three floor levels above grade plane, whereas minimum 2-hour fire barriers are required for control area separations on all floor levels above the third level.

9.   Separated occupancies. The separation of dissimilar occupancies in the same building is accomplished by fire barriers. Table 508.4 is used to determine the required fire-resistance rating of the required fire barriers, ranging from 1 hour through 4 hours.

10.   Fire areas. Where a building is divided into fire areas by fire barriers in order to not exceed the limitations of Section 903.2 for requiring an automatic sprinkler system, the minimum required fire-resistance ratings of the fire barriers are set forth in Table 707.3.10. Ranging from a minimum of 1 hour to a maximum of 4 hours, the fire-resistive requirements are based solely on the occupancy classification of the fire areas. The provisions are applicable to both single-occupancy and mixed-occupancy conditions. See the discussion on Section 901.7 for further information.

Note also that fire barriers are required as separation elements in other miscellaneous locations identified by the code, such as stage accessory areas (Section 410.5) and flammable finish spray rooms (Section 416.2). Throughout the code, references are made to fire barriers as the method of providing the appropriate fire-resistance-rated separation intended. In addition, many of the other International Codes also address the use of fire barriers to create protected areas.

707.5   Continuity.   Fire barriers must begin at the floor and extend uninterrupted to the floor or roof deck above. Where there is a concealed space above a ceiling, the fire barrier must continue through the above-ceiling space. See Figure 707-1. Fireblocking, required only in combustible construction, must be installed at every floor level if the fire barrier contains hollow vertical spaces. The intent of a fire barrier is to provide a continuous separation so as to completely isolate one area from another. As with many other fire-resistance-rated elements, the supporting construction must be of an equivalent rating to the fire barrier supported. A reduction relates to 1-hour incidental use separations in nonrated construction.

Figure 707-1   Fire barrier continuity.

707.6   Openings.   The provisions of Section 716 regulate the protection of openings in fire barriers. The fire-protection ratings mandated for fire-barrier openings in Tables 716.5 and 716.6 vary depending on the fire-resistance rating of the fire barrier as well as its purpose. The required rating may be as little as ¾ hour to as much as 3 hours.

707.9   Voids at intersections. It is not uncommon for a void to be created at the joint between a fire barrier and the floor or roof deck above. Where the joint occurs at a fire-resistance-rated floor or roof deck, Section 715.1 mandates that the joint be protected by an approved fire-resistant joint system. Section 715.1 is also applicable where the joint occurs between a fire barrier and a nonfire-rated floor. Section 707.9 is only intended to address those situations where the roof assembly is not fire-resistance rated. The void need only be protected with an approved material that is securely installed and capable of retarding the passage of fire and hot gases.

Section 708 Fire Partitions

This section regulates the design and construction of fire partitions installed in the listed locations. The IBC identifies six locations where fire partitions are required:

1.   Walls separating dwelling units per Section 420.2

2.   Walls separating sleeping units per Section 420.2

3.   Walls separating tenant spaces in covered and open mall buildings as required by Section 402.4.2.1

4.   Walls of fire-resistance-rated corridors per Section 1020.1

5.   Elevator lobby separation as required by Section 3006.2

6.   Egress balcony separation as required by Section 1019.2

708.3   Fire-resistance rating.   The minimum fire-resistance rating of fire partitions is to be 1 hour, unless a reduction is permitted by one of two exceptions. Exception 1 refers to Table 1020.1, which identifies the required fire-resistance rating of a corridor based on three factors—the occupancy classification of the area served by the corridor, the occupant load the corridor serves, and whether or not the building is sprinklered. Where conditions warrant, the table indicates that the corridor needs only a ½-hour fire-resistance rating. If no fire-resistance rating is mandated, fire partitions are not required and none of the provisions of Section 708 are applicable. The second exception applies to walls separating dwelling units and sleeping units in buildings of nonrated construction. The presence of an automatic sprinkler system complying with NFPA 13 reduces the required fire-partition rating to 30 minutes. It should be noted that the exception does not permit this reduction where an NFPA 13R system is installed.

708.4   Continuity.   Consistent with the required continuity of fire barriers, the general requirement for fire partitions is that they must extend from the floor to the floor or roof deck above. However, unlike the provisions for fire barriers, an alternative construction method is permitted where fire partitions may terminate short of the floor or roof deck under various conditions. Where a fire-resistance-rated floor/ceiling or roof/ceiling is provided, a fire partition need only extend to, and be securely attached to, the ceiling membrane. For an example of this provision as it relates to corridor construction, refer to Figure 708-1. Under this condition in combustible construction, fireblocking or draftstopping must be installed at the partition line in the concealed space above the ceiling. Any supporting construction is to be at least 1-hour fire-resistance rated, except for tenant and sleeping unit separation walls and corridor walls in buildings of Type IIB, IIIB, and VB construction.

Figure 708-1   Corridor fire partitions.

The following exceptions modify the continuity provisions of this section:

1.   Where a crawl space exists below a floor assembly of at least 1-hour fire-resistance-rated construction, the fire partition does not need to extend into the underfloor space. See Figure 708-2.

2.   The arrangement shown in Figure 708-3 would meet the code requirement for adequately enclosing a corridor. The corridor walls are protected on the side of the occupied use spaces by a fire-resistance-rated membrane extending from the floor to the floor or roof above. In this case, the ceiling over the corridor may be considered part of a fire-resistance-rated floor or roof assembly, and the corridor side of the ceiling protected by appropriate ceiling materials would satisfy the fire-resistance rating for the assembly.

3.   The code provides that the corridor ceiling may be of the same construction as permitted for corridor walls as shown in Figure 708-4. In all probability, typical wall construction might not pass the 1-hour test when tested in a horizontal position. However, this arrangement, generally referred to as tunnel construction, is considered to be adequate protection for the corridor separating it from the spaces above.

By establishing various methods for the enclosure of fire-resistance-rated corridors, the code is essentially attempting to get a minimal separation between the exit corridor and the occupied-use spaces. Any arrangement of the 1-hour fire-resistance-rated construction that effectively intervenes between these use spaces and the corridor would satisfy this requirement.

4.   In covered mall buildings, fire partitions separating tenant spaces may terminate at the underside of a ceiling, even if the ceiling is not part of a fire-resistance-rated assembly. No type of extension of the fire partition is required by this section for attics and similar spaces above the ceiling.

5.   In attic areas of Group R-2 occupancies less than five stories in height above grade plane, the draftstopping or fireblocking required by this section may be omitted where the attic area is subdivided by draftstopping into areas not exceeding two dwelling units or 3,000 square feet (279 m²), whichever is less. This exception is also found in Section 718.4.2.

6.   In combustible buildings where the fire partitions stop at the fire-resistance-rated ceiling membrane, fireblocking or draftstopping is not required at the partition line if the building is fully sprinklered. Under this exception, sprinklers must be installed in the combustible floor/ceiling and roof/ceiling spaces. Exceptions in Sections 718.3.2 and 718.4.2 provide the same criteria.

Figure 708-2   Fire partitions above a crawl space.

Figure 708-3   Corridor construction.

Figure 708-4   Tunnel corridor.

Section 709 Smoke Barriers

Smoke barriers, both vertical and horizontal, are occasionally mandated by the code to resist the passage of smoke from one area to another. The use of smoke barriers is assigned to those portions of buildings intended to provide refuge to occupants who may not be able to exit the building in a timely manner. In such cases, relocation, rather than evacuation, is the initial approach to an emergency condition. For example, smoke barriers are used in areas of refuge (Section 1009.6.4), in smoke-control systems (Section 909.5), in Group I-3 occupancies (Section 408.6), and in various other building areas where smoke transmission is a concern. By far the most common use of smoke barriers is in Group I-2 occupancies, where they are used to create smoke compartments (Section 407.5). Smoke barriers must not only resist the passage of smoke, they must also be of minimum 1-hour fire-resistance-rated construction. In Group I-3 occupancies, an exception permits the use of 0.10-inch-thick (2.5-mm) steel in lieu of 1-hour construction.

The key to the construction of a smoke barrier is that all avenues for smoke to travel outside of the compartment created by the smoke barrier are eliminated. This requires the membrane to be continuous from outside wall to outside wall where creating smoke compartments in Group I-2 and I-3 occupancies, and from the floor slab to the floor or roof deck above. The smoke barriers must continue through all concealed spaces, such as those above ceilings, unless the ceilings provide the necessary resistance against fire and smoke passage. In buildings of rated construction, all smoke barriers shall be supported by construction consistent with the fire-resistance rating of the wall or floor supported.

All door openings in smoke barriers are to be protected with assemblies having a minimum fire-protection rating of 20 minutes, per Table 716.5. In cross-corridor situations in Group I-2 occupancies, the code mandates a pair of opposite-swinging doors installed without a center mullion. Such doors shall be provided with an approved vision panel; be close fitting; have no louvers or grilles; and undercuts are limited to ¾ inch. Although positive latching is not required, the doors are to have head and jamb stops, astragals, or rabbets at meeting edges, and automatic-closing devices.

Smoke barriers, like smoke partitions regulated by Section 710, are only mandated where specifically identified by the code. As an example, Section 509.4.2 requires the use of “construction capable of resisting the passage of smoke” as a potential physical separation for incidental uses. Thus, only construction that will perform the intended function is required, and not necessarily a smoke barrier or smoke partition.

Section 710 Smoke Partitions

Unlike the other separation elements used in the code, such as fire walls and smoke barriers, smoke partitions are not specifically defined. Their definition is simply a function of the requirements of Section 710. The purpose of a smoke partition is limited to the concerns of smoke movement under fire conditions, with no intent to regulate for the resistance to flame and heat.

Smoke partitions are mandated by the code in limited applications, most commonly in the construction of corridors in Group I-2 occupancies. As such, corridors in hospitals, nursing homes, and similar Group I-2 occupancies are regulated by the provisions of both Sections 710 and 407.3. It requires a comparison of the two sections to determine the requirements for corridor systems, particularly corridor doors and air openings.

710.5   Openings. This section prohibits the installation of louvers in doors in smoke partitions. This is consistent with the provisions of Section 407.3.1 mandating an effective barrier against the transfer of smoke. The provisions of this section also require that doors in smoke partitions be tested in accordance with UL 1784 and be self-closing or automatic closing, but only where required elsewhere in the code. A review of Section 407.3.1 regulating corridor doors in Group I-2 occupancies does not require the UL test, and it specifically states that self-closing or automatic-closing devices are not required. In this case, the provisions in Section 407.3.1 take precedence.

710.8   Ducts and air transfer openings.   The provisions of both Sections 717.5.7 and 710.8 mandate the need for smoke dampers in air transfer openings that occur in smoke partitions. Smoke dampers are not required at duct penetrations of smoke partitions, but only at unducted air openings.

Section 711 Floor and Roof Assemblies

This section is applicable where floor and roof assemblies are required to have a fire-resistance rating. This will occur where the type of construction mandates protected floor and roof assemblies, such as in Type I, IIA, IIIA, and VA construction, and where the floor assembly is used to separate occupancies or create separate fire areas. For example, in a building of Type IIA construction, Table 601 requires minimum 1-hour fire-resistance-rated floor construction. As another example, where the floor separates a Group A-2 occupancy from a Group B, Table 508.4 addressing separated occupancies mandates a 1- or 2-hour separation.

As referenced in Section 420.3, complementary to the provisions of Section 708 for fire partitions, floor assemblies separating dwelling units or sleeping units are required to be of at least 1-hour fire-resistance-rated construction. The exception to Section 711.2.4.3 reduces the required level of protection for the floor assembly to ½ hour in buildings of Type IIB, IIIB, or VB construction, provided the building is protected by an automatic sprinkler system.

711.2.3   Supporting construction.   As a general rule, horizontal assemblies must be supported by structural members or walls having at least the equivalent fire rating as that for the horizontal assembly. For example, in a Type IIA school building of two stories where the floor construction is required to be a 2-hour fire-resistance-rated assembly in order to separate fire areas, any walls or structural members in the first story supporting the second floor would be required to also be of 2-hour fire-resistance-rated construction. This would be the case even though the building generally is required to be only of 1-hour fire-resistance-rated construction. Obviously, if the horizontal assembly is not supported by equivalent fire-resistance-rated construction, the intent and function of the separation are negated if its supports fail prematurely.

711.2.5   Ceiling panels. The protection of a ceiling membrane also includes the adequacy of the panelized ceiling system to withstand forces generated by a fire and other forces that may try to displace the panels. These forces can generate positive pressures in a fire compartment that need to be counteracted. As a result, lay-in ceiling panels that provide a portion of the fire resistance of the floor/ceiling or roof/ceiling assembly should be capable of resisting this upward or positive pressure so that the panels stay in position and continue to maintain the integrity of the system. The code defines the pressure to be resisted as 1 pound per square foot (48 Pa).

711.2.6   Unusable space.   Figure 711-1 illustrates how this provision is applied in regard to unusable spaces such as crawl spaces and attics. For 1-hour fire-resistance-rated floor construction over a crawl space, the ceiling membrane is not necessary in the crawl-space area. Similarly, in 1-hour fire-resistance-rated roof construction, the floor membrane is not required in the attic. Note that the elimination of the membranes in the attic and crawl space is only applicable where the required rating of the floor or roof assembly is a maximum of 1 hour.

Figure 711-1   Omission of ceiling or floor membrane.

Section 712 Vertical Openings

It is well known that one of the primary means for the spread of fire in multistory buildings, particularly older buildings, has been the transmission of hot gases and fire upward through unprotected or improperly protected vertical openings. The primary cause of death in the hotel portion of the MGM Grand Hotel in Las Vegas, Nevada, as a result of the fire in November 1980, was the upward transmission of smoke through inadequately protected elevator shafts, stair shafts, and heating and ventilating shafts. It is because of this potential for fire spread vertically through buildings that this section requires that vertical openings be appropriately regulated. This section identifies the following applications for addressing vertical openings:

1.   The use of a shaft enclosure to protect vertical openings is a time-honored method recognizing that the fire-resistance-rated enclosure of a floor opening provides a near equivalency to a floor with no openings. The shaft enclosure is intended to replace the floor construction with an equal or better degree of fire resistance. A shaft enclosure is often used for vertical opening protection simply because none of the other applications listed in this section are applicable. The specific requirements for shaft enclosures are set forth in Section 713.

2.   Within individual dwelling units, unconcealed vertical openings are permitted provided they connect no more than four stories. The allowance for openings is intended to apply to units that are open vertically with unenclosed stairways and floor spaces, such as lofts. Concealed spaces used for the installation of ducts, piping, and conduit between stories do not fall under this allowance.

3.   In fully sprinklered buildings, the vertical openings created for an escalator may be protected by one of the following two methods:

3.1.   By limiting the size of the openings, along with the installation of draft curtains and closely spaced sprinklers, the code assumes that the vertical openings in sprinklered buildings do not present an untenable condition. The purpose of the required draft curtain is to trap heat so that the sprinklers will operate and cool the gases that are rising. The curtain is not a fabric; it is constructed of materials consistent with the type of construction of the building. In other than mercantile and business occupancies, the use of this method is limited to openings connecting four or fewer stories.

3.2.   Approved power-operated automatic shutters may also be used to cut off the openings between floors. Required to have a minimum fire-protection rating of at least 1½ hours, the shutters shall close immediately upon activation of a smoke detector. Obviously, operation of an escalator must stop once the shutter begins to close.

4.   Penetrations of cables, conduit, tubing, piping, vents, and similar penetrating items are permitted provided the penetrations are protected in conformance with the provisions of Section 714.4. The allowance for vent penetrations only applies to those vents that convey products of combustion as defined in the International Mechanical Code® (IMC®) and is not intended to apply to exhaust ducts.

5.   Joints protected by a fire-resistant joint system, like other building elements protected by approved methods, do not create any additional hazard that needs to be addressed.

6.   As an alternative to the use of shaft enclosures for ducts penetrating floor systems, the provisions of Section 717.6 also regulate the penetration of ducts through horizontal assemblies. If the provisions of Section 717.6 do not mandate the installation of a damper, the provisions of Sections 713.1.1 and Sections 714.2 through 714.3.3 are applicable. Where Section 717.6 mandates a damper in the duct or air transfer opening, then Section 717 applies.

7.   Atriums are intended to be open vertically. Where such special building features are designed and constructed in compliance with their own unique provisions, other means of vertical opening protection are not required. The use of an atrium is a design option, voluntarily applied by the designer, and thus typically provided as an alternative to a shaft enclosure. For further information, see the discussion of Section 404.

It is a widely held belief that the allowance for atriums is also applicable to covered mall buildings that meet the special requirements of Section 402. However, there is no specific provision in Section 712 that specifically addresses multistory covered mall buildings. Vertical openings in the mall portion of the building could be regulated under the provisions of Sections 712.1.7, 712.1.9, and 712.1.12, but a general allowance for the entire building is not available.

The use of Section 712.1.7 is typically limited to those buildings where the floor openings connect three or more stories. Where a floor opening connects only two stories, Sections 712.1.9 and 712.1.12 are commonly applied.

8.   A masonry chimney extending through one or more floor levels is permitted where the annular space around the chimney is protected in the manner specified by Section 718.2.5.

9.   This provision permits two adjacent stories to intercommunicate with each other without protection of the openings between the two stories, except in the case of Group I-2 and I-3 occupancies. As long as these intercommunicating openings serve only the one adjacent floor, no protection is required. This provision is commonly used where multistory office buildings have a lobby that extends up through the second story so that individuals on the second floor may look down over a guard into the lobby below. It is important that the unprotected floor opening be appropriately separated from floor openings serving other floors.

In addition, the opening between floor levels cannot be concealed within the construction of a wall or floor-ceiling assembly. The limitation on concealment is intended to prevent unprotected openings that are completely enclosed by walls, partitions, chases, or floor/ceiling assemblies. Where the openings are concealed in this manner, they permit a fire within the concealed space to burn undetected and distribute products of combustion to the upper floor.

10.   Automobile ramps in both enclosed and open parking garages, when in compliance with the provisions of Sections 406.5 and 406.6, respectively, are permitted. Because the nature of these uses makes it impractical for enclosures, other safeguards are provided by the code in Section 406.

11.   The enclosure of elevator hoistways in open parking garages and enclosed parking garages is not required for those hoistways that only serve the parking garage.

12.   Vertical opening protection is not mandated for the enclosure of mechanical exhaust and supply duct systems in both types of garage facilities. The protection of vertical openings provided to accommodate elevators, as addressed in Section 712.1.10.2, as well as exhaust ducts and supply ducts, is unnecessary since the vehicle ramps of open and enclosed parking garages are permitted to be open at all levels.

13.   By definition, a complying mezzanine is intended to be open into the room below. As such, unenclosed floor openings between the mezzanine and the lower floor are permitted.

14.   Exit access stairways in compliance with an exception to Section 1019.3 do not require enclosure. For example, under Exception 1, stairways may be unenclosed provided they connect no more than two stories and are not open to any other stories in the building.

15.   Floor fire door assemblies and ceiling access doors are permitted to protect vertical openings where tested in accordance with the applicable standard.

16.   In a Group I-3 occupancy, openings in floors within a housing unit are permitted without a shaft enclosure provided four specific conditions established in Section 408.5 are met.

17.   The installation of unprotected skylights and other penetrations through the roof deck of a fire-resistance-rated roof assembly is permitted, provided the structural integrity of the roof construction is maintained.

18.   Throughout the code, there may be other allowances for floor penetrations or openings that are adequately regulated as vertical openings. Where permitted, these openings must comply with the specifics of their use.

Section 713 Shaft Enclosures

The use of a shaft enclosure has long been an acceptable means to protect vertical openings between stories. The enclosure construction is considered to be equivalent to the floor system and thus is permitted to protect any opening that occurs. Although using a shaft enclosure is just one of many applications listed in Section 712.1 for addressing vertical openings, its use is very common, particularly in buildings with a substantial number of stories. In some buildings, the use of a shaft enclosure is the only viable application available.

713.4   Fire-resistance rating.   To provide an acceptable level of protection for vertical openings between floors, this section mandates that all shaft enclosures have a fire-resistance rating at least equivalent to the rating of the floor being penetrated, but never less than 1 hour. Therefore, in Type I construction, or where the shaft enclosure connects four or more stories, a minimum 2-hour enclosure is mandated. A shaft enclosure is never required to have a higher fire-resistance rating than 2 hours.

713.5   Continuity. Shaft enclosures are required to be constructed as fire barriers, extending from the top of the floor/ceiling assembly below to the underside of the floor or roof deck above, except as permitted by Sections 713.11 and 713.12. It is important that the walls continue through any concealed spaces such as the area above a ceiling, and that any hollow vertical spaces within the shaft wall be fireblocked at each floor level in buildings of combustible construction. In addition, the supporting elements of any shaft enclosure construction must be of fire-resistance-rated construction equivalent to that of the shaft construction. The enclosure, fire-resistance-wise, should be continuous from the lowest floor opening through to its termination.

713.6   Exterior walls.   Unless required to be fire-resistance rated because of the proximity to an exterior exit balcony, interior exit stairway or ramp, or an exterior exit stairway or ramp, the exterior walls of a shaft enclosure need only be protected because of their location on the lot as regulated by Section 705.

713.11   Enclosure at the bottom.   Many shafts do not extend to the bottom of the building or structure. Therefore, it is necessary to provide an approved method for maintaining the integrity of the shaft enclosure at its lowest point. This section identifies three methods for enclosing the bottom of a shaft enclosure. First, the shaft can be enclosed with fire-resistance-rated construction equivalent to that for the lowest floor penetrated, with a minimum rating consistent with that of the shaft enclosure. Second, a termination room related to the purpose of the shaft can be considered to be the enclosure at the bottom, provided the room is separated from the remainder of the building with fire-resistance-rated construction and opening protectives equivalent to those of the shaft enclosure. Third, approved horizontal fire dampers can be used to protect openings at the lowest floor level in lieu of the enclosure at the bottom of the shaft enclosure. See Figures 713-1a, b, and c.

Figure 713-1   Enclosure at shaft bottom.

The first of the three exceptions eliminates the fire-resistance-rated room separation where there are no other openings into the shaft enclosure other than at the bottom. All portions of the enclosure bottom must be closed off except for the penetrating items, unless the room is provided with an automatic fire-suppression system. An example of this concept would be a vent enclosure. The second exception requires that a shaft enclosure containing a refuse or laundry chute be used for no other purpose and shall end in a termination room per Section 713.13.4. Exception 3 applies where the shaft enclosure contains no combustible materials. In this situation, there is no need for either the fire-resistance-rated room separation or protection at the bottom of the enclosure. An example would be a light well that extends through several floor levels to the roof, as illustrated in Figure 713-2. It would be considered an extension of the floor below the level of the floor opening.

Figure 713-2   Vertical shafts—bottom enclosure.

713.12   Enclosure at the top. Most shafts extend to or through the roof deck at the exterior, where there is no requirement to maintain the fire-resistance rating of the shaft enclosure construction. However, where the enclosure does not extend to the roof, the top of the shaft must be enclosed. The required fire-resistance rating of the shaft lid shall be equivalent to the rating of the topmost floor penetrated by the shaft, but in no case less than the fire-resistance rating required for the shaft. See Figure 713-3 for two examples that illustrate the termination requirements.

Figure 713-3   Top enclosure of shaft.

713.13   Refuse and laundry chutes.   The requirements of this section are intended to further strengthen the shaft-enclosure provisions where chutes and discharge rooms for refuse or laundry are constructed. Refuse and laundry areas are often poorly maintained, with a greater potential for a fire incident than most other areas of a building. Coupled with the shaft conditions that are created by the chutes, these types of areas pose hazards that exceed those typically encountered. See Figure 713-4. To further secure the intent, Section 903.2.11.2 requires sprinkler protection for the chutes and termination rooms.

Figure 713-4   Rubbish and linen chutes.

Refuse and laundry chutes are regulated by both the IBC and Chapter 5 of NFPA 82, Standard on Incinerators and Waste and Linen Handling Systems and Equipment. In order to eliminate any inconsistencies between the IBC and NFPA 82 regarding such chutes, the standard is directly referenced in lieu of the IBC for the applicable construction requirements.

Section 714 Penetrations

The integrity of fire-resistance-rated horizontal and vertical assemblies is jeopardized where penetrations of such assemblies are not properly addressed. Cables, cable trays, conduit, tubing, vents, pipes, and similar items are those types of penetrating items regulated by the code. This section of the IBC identifies the appropriate materials and methods of construction used to protect both membrane penetrations and through penetrations.

714.1.1   Ducts and air transfer openings.   Section 717.5 identifies the various conditions under which fire-resistance-rated wall assemblies penetrated by ducts or air transfer openings must be provided with fire and/or smoke dampers. There are a limited number of locations where a damper is not required, such as that permitted by Exception 3 of Section 717.5.2 for fire barrier penetrations and Exception 4 of Section 717.5.4 for fire partitions. See Figure 714-1. In such situations, it is necessary that the penetrations be protected in accordance with the appropriate provisions of Section 714 in order to maintain the integrity of the fire-resistive assembly.

Figure 714-1   Duct penetration of 1-hour fire barrier.

714.2   Installation details.   As illustrated in Figure 714-2, sleeves used in the process of creating a through-penetration of a fire-resistance-rated building element must be properly installed. They must be securely fastened to the assembly that is being penetrated. In addition, both the space between the sleeve and the assembly and the space between the sleeve and the penetrating item must be appropriately protected.

Figure 714-2   Penetration sleeve.

714.3   Fire-resistance-rated walls. This section regulates the penetration into or through fire walls, fire barriers, fire partitions, and smoke barrier walls. The protection of penetrations in fire-resistance-rated exterior walls is not addressed; however, where such exterior walls are bearing walls it is necessary to consider penetration protection in order to maintain the structural integrity of the walls during fire conditions. Fire-resistance-rated interior bearing walls are also not specifically identified as elements regulated for penetrating items; however, any penetrations of such walls should be addressed in order to maintain the necessary structural fire resistance. For the most part, membrane penetrations are addressed in the same manner as through penetrations.

714.3.1   Through-penetrations.   As a general rule, through-penetrations (where the penetrating items pass through the entire assembly) are required to be firestopped with approved through-penetration firestop systems when the penetrations pass through fire-resistance-rated walls, unless the approved wall assembly is tested with the penetrations as a part of the assembly. The firestop system is required to have an F rating at least equivalent to that of the fire-resistance rating of the wall penetrated, as shown in Figure 714-3. There is no requirement for a T rating on a wall penetration, justified on the basis that there is no need for such a restrictive temperature rating for the penetration of wall assemblies.

Figure 714-3   F rating required.

The IBC contains an exception to the general rule for firestopped wall penetrations allowing small noncombustible penetrating items no larger than 6-inch (152-mm) nominal diameter to penetrate concrete or masonry walls, provided the full thickness of the wall, or the thickness required to maintain the fire resistance, is filled with concrete, grout, or mortar. The size of the opening is limited to 144 square inches (0.0929 m²). A second exception that is used extensively will allow the annular space around the same type of noncombustible penetrating item to be filled with a material that prevents the passage of flame or hot gases sufficient to ignite cotton waste when tested under the time-temperature fire conditions of ASTM E 119 or UL 263, and under a positive pressure differential of 0.01-inch (0.25-mm) water column. When properly installed around the penetrations of noncombustible items, these materials provide adequate firestopping between the penetrating item and the fire-resistive membrane of the wall. See Figure 714-4.

Figure 714-4   Through-penetrations of wall.

714.3.2   Membrane penetrations. This section addresses penetrations through a single membrane of fire-resistance-rated walls. For the most part, a membrane penetration is to be protected by one of the methods established for through-penetrations as previously described. However, there are some membrane penetrations that are allowed without a specific firestopping material in the annular space around such penetrations. Openings for steel electrical boxes are specifically addressed where located in walls with a maximum 2-hour rating, provided that they are no more than 16 square inches (0.0103 m²) in area and the aggregate area of the boxes does not exceed 100 square inches (0.0645 m²) for any 100 square feet (9.29 m²) of wall area. The annular space between the wall membrane and any edge of the electrical box is limited to ⅛ inch (3.1 mm). Also, to prevent an indirect through-penetration, electrical boxes on opposing sides of a fire-resistance-rated wall shall be horizontally separated by no less than 24 inches (610 mm). As an alternative, boxes may be separated horizontally by the depth of the cavity if the cavity is filled with cellulose loose-fill, rockwool, or slag mineral wool insulation; by solid fireblocking in accordance with Section 718.2.1; by protection of both outlet boxes with listed putty pads; or by any other listed methods and materials. Examples of several of these methods are illustrated in Figure 714-5.

Figure 714-5   Penetration of fire-resistance-rated walls.

A second exception for membrane penetrations of electrical-outlet boxes allows outlet boxes of any material, provided they are tested for use in fire-resistance-rated assemblies and installed in accordance with the instructions for the listing. Limitations are also placed on the annular space surrounding the box and conditions where the boxes are placed on opposite sides of the wall. Exception 3 allows for penetrations by electrical boxes of any size or type provided they are listed as a part of a wall opening protective material system, while Exception 4 addresses boxes, other than electrical boxes, that have annular space protection provided by an approved membrane penetration firestop system. The fifth exception permits the annular space created by the penetration of a fire sprinkler to be unprotected, provided that such a space is covered by a metal escutcheon plate. Because the escutcheon is a part of the listed sprinkler, it is inappropriate to require firestopping at this location. It should be noted that this exception applies to the penetration of sprinklers, not simply sprinkler piping or cross mains that might be penetrating fire-resistance-rated construction. See Figure 714-6. Exception 6 addresses steel electrical boxes that exceed 16 square inches (0.0103 m²) in area as well as those where the aggregate area of the boxes exceed 100 square inches (0.0645 m²) in any 100 square feet (9.29 m²) of wall area.

Figure 714-6   Membrane penetration protection.

714.3.3   Dissimilar materials.   This provision is intended to limit the occasional practice of using a noncombustible penetrating item (such as a short metal coupling) to penetrate a fire-resistance-rated wall, then connect to a combustible item (such as plastic piping or conduit) on the room side of the wall. The building official can accept such a condition where it is demonstrated that the fire-resistive integrity of the wall will be maintained. See Figure 714-7.

Figure 714-7   Membrane penetrations of walls.

714.4   Horizontal assemblies. The shaft enclosure provisions of Section 713 intend to maintain a level of protection that is compromised when one or more openings occur in a floor or floor/ceiling assembly. However, penetrations by pipes, tubes, conduit, wire, cable, and vents are permitted without shaft enclosure protection where in compliance with this section. In addition, this section addresses penetrations that occur in the ceiling of a roof/ceiling assembly. Penetrations occurring in both fire-resistance-rated horizontal assemblies and nonfire-resistance-rated assemblies are addressed.

714.4.1   Through-penetrations. The protection requirements for the through-penetration of fire-resistance-rated horizontal assemblies are very similar to those required for vertical elements. The general provisions state that the penetrations are to be installed as tested in an approved fire-resistance-rated assembly or protected by an approved through-penetration firestop system. Where a firestop system is used, it must have both an F rating and a T rating equivalent to the floor penetrated, but in no case less than 1 hour. Only an F rating is needed if the penetrating item, as it passes through the floor, is contained within a wall cavity above or below the floor. See Figure 714-8. Exception 2 indicates that a T rating is also not required where the floor penetration is a floor drain, tub drain, or shower drain.

Figure 714-8   Through-penetrations of horizontal assemblies.

Noncombustible penetration items are granted exceptions to the general requirements as previously discussed for fire-resistance-rated walls. Where only a single fire-resistance-rated floor is penetrated, the annular space around the noncombustible penetration item need only to be protected with an approved material that fills the opening. There is no limit on the size of the penetrating items, provided they are appropriately protected. Where multiple floor assemblies are penetrated, the size of any penetrating item is limited to 6 inches (152 mm) in nominal diameter. In addition, the area of the penetration is limited to 144 square inches (92,900 mm²) in any 100 square feet (93 m²) of floor area. Figure 714-9 depicts the use of this exception. Allowances are also provided for noncombustible penetrations of concrete floors as well as for tested electrical outlet boxes.

Figure 714-9   Penetrations of horizontal assemblies.

714.4.2   Membrane penetrations. Fire-resistance-rated horizontal assemblies must be adequately protected at penetrations of the floor or ceiling membrane. Therefore, they are regulated in the same manner as through-penetrations addressed in Section 714.4.1. The code also specifies that any recessed fixtures that are installed in fire-resistance-rated horizontal assemblies shall not reduce the level of required fire resistance. Exceptions to the general requirement for approved firestop systems apply to noncombustible penetrations, steel electrical boxes, boxes listed as part of an opening protective material system, listed electrical-outlet boxes, fire sprinklers, and noncombustible items cast into concrete building elements. See Figure 714-10.

Figure 714-10   Membrane penetrations of horizontal assemblies.

Exception 7 allows for the practical application of the code where wood-framed walls extend up and attach directly to the underside of wood floor joists/trusses or roof joists/trusses for structural requirements. However, there are limits to its use. Nonfire-rated wall top plates are not allowed to interrupt the gypsum-board membrane of the floor/ceiling or roof/ceiling membrane. The allowance is only permitted where the horizontal assembly has a required fire-resistance rating of 2 hours or less, and the intersecting wall must be sheathed with Type X gypsum wallboard. Piping, conduit, and similar items within the fire-resistance-rated wall must be adequately protected where they penetrate the double-wood top plate. Compliance with the established criteria is deemed to provide for an equivalent degree of fire resistance at the discontinuous portion of the ceiling membrane at the intersection of a horizontal assembly and a fire-resistance-rated wall with a double-wood top plate. See Figure 714-11.

Figure 714-11   Horizontal assembly continuity at fire-rated wall.

714.5   Nonfire-resistance-rated assemblies.   Figure 714-12 illustrates the provisions for penetrations of those horizontal assemblies not required to have a fire-resistance rating. Section 713 for shaft enclosures will regulate such penetrations where the allowances set forth in this section are not applicable. Where penetrations connect only two stories, the annular space around the penetrating items must simply be protected with a material that resists the free passage of fire and smoke. If the penetrating items are noncombustible, up to three stories may be connected, provided the annular space is filled appropriately.

Figure 714-12   Nonfire-resistance-rated assemblies.

Section 715 Joint Systems

A fire-resistant joint system is defined in Section 202 as “an assemblage of specific materials or products that are designed, tested, and fire-resistance rated in accordance with either ASTM E 1966 or UL 2079 to resist, for a prescribed period of time, the passage of fire through joints made in or between fire-resistance-rated assemblies.” The term joint is also defined as “the linear opening in or between adjacent fire-resistance-rated assemblies that is designed to allow independent movement of the building, in any plane, caused by thermal, seismic, wind or any other loading.” The approved joint system should be designed to resist the passage of fire for a time period not less than the required fire-resistance rating of the floor, roof, or wall in or between which it is installed. See Figure 715-1.

Figure 715-1   Fire-resistant joint systems.

The code lists nine locations where it is not necessary to provide fire-resistant joint systems. For most of the applications listed, they are also locations where fire assemblies are not required to protect openings in the horizontal or vertical assemblies. Item 9 references maximum ⅝-inch (15.9-mm) control joints when tested in accordance with ASTM E 119 or UL 263.

715.4   Exterior curtain wall/floor intersection.   Vertical passages without barriers allow fire and hot gases to circumvent the protection for occupants in the floors above. When floors or floor/ceiling assemblies do not extend to the exterior face of a building, this section requires an approved barrier at the intersection at least equal to the fire resistance of the floor or floor/ceiling assembly. See Figure 715-2.

Figure 715-2   Exterior curtain wall/floor intersection.

ASTM E 2307 is identified for the specification and testing methods used to determine the necessary fire resistance. This test method measures the performance of a perimeter fire-barrier system and its ability to maintain a seal to prevent fire spread during the deflection and deformation of the exterior wall assembly and floor assembly expected during a fire condition, while resisting fire exposure from both an interior compartment and the flame plume emitted from a window burner below.

A minimum level of protection is also mandated at any voids created at the intersection of an exterior curtain wall and a nonrated floor or floor assembly. The required method is consistent with that required in the code for the penetration of ducts and other items through nonfire-resistance-rated floor systems. The protection of the annular space is provided through the installation of an approved noncombustible material that resists the free passage of flame and the products of combustion.

Section 716 Opening Protectives

In the context of the IBC, an opening protective refers to a fire door, fire shutter, or fire-protection-rated glazing, including the required frames, sills, anchorage, and hardware for its proper operation. Generally, whenever any fire door, fire shutter, or fire-protection-rated glazing is referred to, it is the intent of the code that the entire fire assembly be included.

716.2   Fire-resistance-rated glazing. This section is an extension of the provisions in Section 703.6 regarding the use of fire-resistance-rated glazing. Where such glazing is appropriately tested and labeled, its use is permitted in fire doors and fire window assemblies as specified in Table 716.5. Such glazing tested as part of a wall assembly per ASTM E 119 or UL 263 is not required to comply with the provisions of Section 716 where used as a part of the wall.

716.3.3   Fire-rated glazing that exceeds the code requirements. Both fire-resistance-rated glazing and fire-protection-rated glazing must be appropriately identified for verification of their appropriate application. These markings establish compliance with hose-stream and temperature rise requirements, while also identifying the minimum assembly rating in minutes. It is not unusual for such glazing to be marked indicating a higher degree of protection than mandated by the code. This provision clarifies that the use of glazing marked to indicate a higher level of compliance is permitted for use where such compliance is not required.

Table 716.3 defines and relates the various test standards for fire-rated glazing to the designations used to mark such glazing. The table reflects the use of the designations “W,” “OH,” “D,” “T,” “H,” and “XXX” as markings for fire-rated glazing. Tables 716.5 and 716.6 set forth the markings required for acceptance in specified applications. The marking of fire-rated glazing does not include the “NH” (not hose-stream tested) and “NT” (not temperature-rise tested) designations, as these designations correspond with test standards, not end uses.

716.5   Fire door and shutter assemblies.   This section sets forth the test standards and additional criteria necessary for the acceptance of fire door and fire shutter assemblies. In addition, Table 716.5 identifies the minimum fire-protection rating for an opening protective based on the type of assembly in which it is installed. For example, a door assembly in a 1-hour fire barrier wall separating hazardous material control areas would need to have a minimum ¾-hour fire-protective rating, whereas a 1-hour fire-resistance-rated interior exit stairway enclosure would require a minimum 1-hour door assembly.

Side-hinged or swinging doors are to be tested for conformance with NFPA 252 or UL 10C. It is important that the NFPA 252 test provides for positive pressure in the furnace as established by this section. See Figure 716-1. For other types of doors, the pressure level need only be maintained as nearly equal to the atmosphere’s pressure as possible.

Figure 716-1   Fire test of door assemblies.

716.5.3   Door assemblies in corridors and smoke barriers.   Fire door assemblies located in fire-resistance-rated corridor walls or smoke barrier walls are further regulated where required by Table 716.5 to have a 20-minute fire-protection rating. They are commonly referred to as smoke- and draft-control assemblies. Their primary purpose is to minimize smoke leakage around the door and through the opening. For this reason, these doors shall not contain louvers and must be installed in accordance with NFPA 105.

The protection of fire-rated corridors is intended to be a two-way protection. Although the general intent is to protect the corridor from smoke that might be generated by a fire occurring within the adjacent use spaces, there are occasions where it is just as important to protect the occupied use spaces from smoke in the corridor. The fire test for corridor and smoke-barrier doors is essentially the same test of the door as for other fire-door assemblies, except that the fire test for the 20-minute assembly does not include the hose-stream test. In addition, Section 716.5.3.1 requires the door assembly to be tested for smoke infiltration through the UL 1784 air leakage test and identifies the criteria for acceptance. Note that glazing other than in the door itself, such as in sidelites or transoms, must be tested with the hose-stream test as set forth in NFPA 257 or UL 9.

An exception permits the installation of a viewport through the door for purposes of observation. These viewports must be installed under the limitations of, and in accordance with, the conditions specified in the exception. Corridor door provisions are modified in Section 407.3.1 for Group I-2 occupancies and in multitheater complexes as shown in Figure 716-2. In addition, where horizontal sliding doors are used in smoke barriers of Group I-3 occupancies as specified, the 20-minute fire-protection rating is not required.

Figure 716-2   Corridor doors in a multitheater complex.

716.5.5   Doors in interior exit stairways and ramps and exit passageways.   In addition to the normal requirement for fire doors, the IBC is concerned that fire door assemblies installed in enclosures for interior exit stairways/ramps and exit passageways shall be capable of limiting the temperature transmission through the door. It specifies that the temperature rise above ambient temperature shall be limited to a maximum of 450°F (232°C) at the end of 30 minutes of the normal fire test. However, in buildings equipped with an automatic sprinkler system, the temperature limitation is not applicable.

The purpose of these highly protected exit elements and their openings is to protect the building occupants while they are exiting the building. It is intended that in a properly enclosed and protected interior exit stairway or ramp enclosure, building occupants from the floors above the fire floor will be able to pass through the fire floor inside the enclosure and eventually pass down and out of the building. The end-point limitation on temperature transmission through the fire door, then, is literally to protect the person inside the enclosure from excessive heat radiation from the fire door as he or she passes through the fire floor. In sprinklered buildings, the maximum transmitted temperature end point is not required. It is expected that a sprinkler system will limit the fire growth to the point where such extra care is unnecessary.

716.5.7   Labeled protective assemblies.   Fire doors are required to have an approved label or listing mark permanently affixed at the factory. The label must contain information that identifies the manufacturer, the third-party inspection agency, and the fire-protection rating. Where applicable, the maximum transmitted temperature end point or the smoke- and draft-control designation must be identified.

Listing agencies will typically only label door assemblies that have been tested. However, some door assemblies are too large to be tested in available furnaces. As a result, the code permits the installation of oversized fire doors under the conditions of this section. As oversized fire doors are not subjected to the standard fire test, an approved testing agency must provide a certificate of inspection from them certifying that, except for the fact that the doors are oversized, they comply with the requirements for materials, design, and construction for a fire door of the specified fire-endurance rating. An approved agency may also provide a label on the door indicating it is oversized. Where the certificate or label of an approved agency has been provided, there is assurance that the fire door will protect the opening as required by the code.

The letter “S” on a fire door indicates that it is in compliance with UL 1784, the air leakage testing. Through this identifying mark, it is possible to quickly identify the door as appropriate where smoke and draft control doors are mandated.

Individual components, such as vision panels, may be installed in labeled fire doors provided such components are listed or classified and labeled for use by a third-party agency.

716.5.8.1   Size limitations.   Fire-protection-rated glazing is permitted in wall assemblies rated at 1 hour or less when in compliance with the size limitations of NFPA 80. Where a fire wall or fire barrier requires a rating greater than 1 hour, such glazing is prohibited except for two conditions. First, fire-protection-rated glazing may be used as vision panels in swinging fire door assemblies serving as horizontal exits when limited in size. Owing to the use of a horizontal exit as a required means of egress, it is often beneficial to provide a glass light of limited size so that occupants may view the egress path ahead of them. Second, the maximum size of all types of fire-protection-rated glazing in 1½-hour fire doors is limited to 100 square inches (0.065 m²) when installed in a fire barrier.

716.5.8.3   Labeling.   Glazing used in fire door assemblies must be identified for verification of its appropriate application. As established in Table 716.3, the “D” designation indicates the glazing can be used in a fire door assembly, with the remaining identifiers providing specific information as to the glazing’s capability to meet the hose-stream test and temperature limits. See Figure 716-3.

Figure 716-3   Identification of glazing in fire doors.

716.5.9   Door closing.   The code mandates that fire doors be provided with closers to allow them to shut and protect the opening without manual operation. One exception to this broad-based requirement applies to those fire doors located in the common walls between sleeping units of hotels and motels. These doors are so seldom open that it is unreasonable to require door-closing hardware.

716.5.9.2   Automatic-closing fire door assemblies. Where automatic-closing devices are used instead of self-closing devices on fire doors, they must also comply with the provisions of NFPA 80 for self-closing action. Although they are generally held in an open position, doors equipped with automatic-closing devices become self-closing when actuated. The use of automatic-closing devices is typically a design decision; however, the code does mandate such devices in two applications. Automatic-closing devices are required by Section 709.5.1 on cross-corridor doors located in Group I-2 occupancies and ambulatory care facilities. They must also be installed on cross-corridor doors located in a horizontal exit as set forth in Section 1026.3.

716.5.9.3   Smoke-activated doors.   This section identifies 12 locations where a smoke detector is to be used to actuate the closing operation for an automatic-closing fire door where such a closing device is provided. The detectors must be installed in accordance with the provisions of Section 907.3 and, furthermore, they must be of an approved type that will release the door in the event of a power failure. Automatic-closing fire door assemblies are often used to increase the reliability of the opening protection. Swinging fire doors with self-closers are all too often propped open with wood blocks or wedges. Although this section regulates the method for activating automatic-closing fire doors, it does not identify where automatic-closing doors are mandated.

716.6   Fire-protection-rated glazing.   In many situations, it is necessary to provide glazed openings in fire-resistance-rated walls. The provisions of this section address fire window assemblies installed as opening protectives in fire partitions and exterior walls, as well as in some 1-hour fire barriers.

Fire-protection-rated glazing in fire window assemblies must be tested in accordance with NFPA 257 or UL 9. In addition, they must be installed and sized in accordance with NFPA 80. In all cases, a fire-window assembly must include an approved frame, be fixed in position, or be automatic closing.

In interior applications, fire-protection-rated glazing is limited to fire partitions, smoke barriers, and two types of fire barriers having a maximum fire-resistance rating of 1 hour. The total aggregate area of fire windows cannot exceed 25 percent of the area of the common wall between areas, as shown in Figure 716-4. In making this 25-percent calculation, it is permissible to assume the entire area of the common wall even though a portion of that area might be taken up by doors. This gross area is usable in calculating the maximum percentage of area for windows. Where the ceilings are of different heights, the lower ceiling establishes the gross area.

Figure 716-4   Glazing limitations.

Fire-protection-rated glazing is not permitted to be located in any fire wall or in any fire barrier (with two exceptions); however, Section 716.2 recognizes that glazing tested as a part of a wall assembly is permitted in all applications and, therefore, not regulated by this section. This type of glazing is referred to as fire-resistance-rated glazing, rather than fire-protection-rated glazing, and is further addressed in Section 703.6. In addition, the 25-percent area limitation is not applicable. Glazing that has a fire-resistance rating under ASTM E 119 or UL 263 that meets the fire-resistance rating of the wall may be used in more applications than fire-protection-rated glazing complying with NFPA 257 or UL 9. Also see the discussion of Section 703.6.

Section 717 Ducts and Air Transfer Openings

Where a duct or air transfer opening penetrates a fire-resistance-rated assembly, it is often necessary that a method of protection be provided to maintain the integrity of the assembly. Many times, dampers are used to protect the opening created by the duct or transfer opening. If dampers are not required to be provided under the provisions of this section, it is still necessary to protect the penetration under the provisions of Section 714.1.1.

717.2   Installation.   This section states that fire and smoke dampers shall be installed in accordance with their listing. The test standards for each of the types of damper carry specific requirements that manufacturers provide installation and operating instructions, and that a reference to these instructions shall be a part of the required marking information on the damper.

717.3.1   Damper testing.   Dampers must not only be listed but also bear a label indicating that the damper is in compliance with the appropriate standard as identified by this section. For example, for fire dampers the required information on the damper includes the hourly rating; the words “Fire Damper”; whether or not the damper is to be in a dynamic or static system (or both); maximum rated airflow and pressure differential across the closed damper for dampers intended for use in dynamic systems; an arrow showing direction of airflow for dampers intended for use in dynamic systems; the intended mounting position (vertical, horizontal, or both); top of damper; and, of course, the manufacturer’s name and model number. UL 555 (which applies to fire dampers) requires that all of this information shall be available on the damper label, which is installed at the factory, and that all labels shall be located on the internal surface of the damper and be readily visible after the damper is installed. UL 555 indicates that fire dampers tested under that standard are intended for use in HVAC duct systems passing through fire-resistive walls, partitions, or floor assemblies.

Just as fire dampers are tested for different hourly ratings, they are also tested for different installation positions. A damper listed for vertical installation cannot arbitrarily be installed in the horizontal position.

This section also states that only fire dampers labeled for use in dynamic systems shall be installed in systems intended to operate with fans on during a fire. The test standard for fire dampers states that fire dampers are intended for use in either static systems that are automatically shut down in the event of a fire, or in dynamic systems that are operational in the event of a fire. If the HVAC system has not been designed and constructed to shut down in case of a fire, then dynamically listed fire dampers are necessary. These provisions are also applicable to ceiling radiation dampers. Special attention should be paid to damper listings when smoke-control systems are installed under the provisions of Section 909.

Test standard UL 555S is to be used to determine the compliance of smoke dampers. This standard states that leakage-rated dampers (smoke dampers in the IBC) are intended to restrict the spread of smoke in HVAC systems that are designed to automatically shut down in the event of a fire, or to control the movement of smoke within a building when the HVAC system is operational in engineered smoke-control systems.

In addition to fire dampers and smoke dampers, three other types of dampers are referenced in the IBC. Where combination fire/smoke dampers are provided, they must comply with the requirements of both UL 555 for fire dampers and UL 555S for smoke dampers. Figure 717-1 illustrates the installation of an automatic-closing combination fire and smoke damper. Ceiling radiation dampers, intended for installation in air-handling openings penetrating the ceiling membranes of fire-resistance-rated floor/ceiling and roof/ceiling assemblies, are to meet the conditions of UL 555C.

Figure 717-1   Combination fire and smoke dampers.

Corridor dampers are to be utilized in a specific application, where (1) air ducts penetrate or terminate at horizontal openings, (2) provided such openings occur in the ceiling of a fire-resistance-rated corridor, and (3) if the corridor ceiling is constructed as required for corridor walls as further addressed in Exception 4 of Section 708.4. See Figure 717-2. The listing and testing of a corridor damper is different from the regular combination fire/smoke damper in that the testing is done in a wall assembly installed in the horizontal position.

Figure 717-2

717.3.2.1   Fire damper ratings. Test standard UL 555 covers fire dampers ranging from ½ hour to 3 hours. Because fire dampers carry an hourly rating, plans should reflect the rating required at a particular location if more than one rating is required within a building. Table 717.3.2.1 indicates whether a 1½-hour or 3-hour rating is required for a fire damper, based on the fire-resistance rating of the assembly in which it is installed. In all applications rated at 3 hours or greater, a 3-hour-rated damper is mandated; otherwise, a 1½-hour damper is acceptable.

717.3.2.2   Smoke damper ratings.   A Class I or Class II leakage rating is required for smoke dampers, which also must have an elevated temperature rating of at least 250°F (121°C). The class designation indicates the maximum leakage permitted in cubic feet per minute per square foot (cubic mm per minute per mm²) for the particular class. The four classes progress from Class I (least leakage or best performance) through Class IV (greatest leakage or poorest performance). The IBC requires conformance with Class I or II, so a damper rated as Class III or IV would not be acceptable. These leakage ratings are determined at ambient temperature after exposing the damper to temperature degradation at an elevated temperature, with 250°F (121°C) being the lowest elevated temperature allowed by the code. Dampers can be tested using higher degradation temperatures [one as high as 850°F (454°C)], but most listed dampers seem to have been tested at either 250°F (121°C) or 350°F (177°C).

The provisions of Section 717.3.3.2 specifically instruct the designer or installer on how to control smoke dampers. Smoke dampers are required to be closed by activation of smoke detectors installed in accordance with Section 907.3 for fire-detection systems and any of the five specified methods of control listed in this provision. These methods of control, each having benefits and drawbacks, were proposed by those individuals involved with damper installation and should provide consistent and logical control methods for the dampers.

717.4   Access and identification.   Both fire dampers and smoke dampers shall be installed so that they are accessible for inspection and servicing. It is important that any access openings in a fire-resistance-rated assembly be adequately protected in order to maintain the integrity of the assembly. This will typically involve the use of an access door having the required fire-protection rating. Permanent identification of the access points to fire-damper and smoke-damper locations is also mandated.

717.5   Where required.   This section lists those specific locations where the various dampers are required. Dampers need only be installed in ducts and transfer openings where specifically identified by this section. In some locations, both a fire damper and a smoke damper are required. This means that either two dampers must be installed or a damper listed for both heat and smoke control must be used.

717.5.1   Fire walls.   Because of the importance of maintaining the separation provided by fire walls used to divide a structure into two or more separate buildings, the code requires the use of approved fire dampers under all conditions. Such dampers are to be installed at all permitted duct penetrations and air-transfer openings of fire walls. Where the fire wall serves as a party wall as addressed in Section 706.1.1, ducts and air transfer openings are prohibited. There is no requirement for smoke dampers at duct penetrations and air openings through fire walls except for those fire walls serving as horizontal exits.

717.5.2   Fire barriers. Much like fire walls, fire barriers are designed to totally isolate one area of a building from another. Therefore, the general requirement is that all duct penetrations and air transfer openings of fire barriers be protected by complying fire dampers. There are, however, several exceptions that may eliminate the need for dampers. Of special note is the elimination of fire dampers in certain sprinklered buildings. Fire dampers are not required for duct penetrations and air openings in fire barriers where all of the following conditions exist:

1.   The penetration consists of a duct that is a portion of a ducted HVAC system.

2.   The fire-resistance rating of the fire barrier is 1 hour or less.

3.   The area is not a Group H occupancy.

4.   The building is fully protected by an automatic fire-sprinkler system.

A fire barrier that serves as a horizontal exit must also be provided with a listed smoke damper at each point a duct or air transfer opening penetrates the fire barrier.

717.5.3   Shaft enclosures.   Both a fire damper and a smoke damper, or a combination fire/smoke damper, must be installed where a duct or air transfer opening penetrates a shaft enclosure. Five exceptions identify conditions under which fire dampers are not required. As shown in Figure 717-3, the first exception permits fire dampers to be eliminated where steel exhaust subducts enter an exhaust shaft. The subducts must extend vertically at least 22 inches (559 mm), and there must be continuous air flow upward to the outside through the shaft. Smoke dampers are also not required under similar conditions, but the exception is limited to fully sprinklered Group B and R occupancies where the fan providing continuous airflow is on standby power. Exception 5 exempts fire dampers and fire/smoke dampers in kitchen and clothes dryer exhaust systems due to potential obstruction hazards. Smoke dampers are not addressed in this exception, but may be omitted when Exception 2 is applied.

Figure 717-3   Exhaust subducts penetrating shafts.

717.5.4   Fire partitions. Fire partitions are not regulated by the code as highly as fire barriers or fire walls, so it is consistent that the requirements for dampers through such partitions are not as restrictive. The general rule is that a fire damper is required in any duct or air transfer opening that penetrates a fire partition. However, where the building is fully sprinklered, ducts penetrating tenant separation walls in covered mall buildings or fire-resistance-rated corridor walls need not be fire dampered. In addition, fire dampers are not necessary for small steel ducts installed above a ceiling, provided the duct does not communicate between a corridor and adjacent rooms and does not terminate at a register in a fire-resistance-rated wall. The fourth exception is consistent with Exception 3 of Section 717.5.2 addressing fire barriers.

717.5.4.1   Corridors. Because a fire-resistance-rated corridor is intended to be an exit access component providing a limited degree of occupant protection during egress activities, it is logical that air openings into the corridor be addressed. This section mandates, with exceptions, that all corridors required to be protected with smoke- and draft-control doors shall also be provided with smoke dampers where ducts or air transfer openings penetrate the corridor enclosures. Additional protection is required where ducts and air transfer openings penetrate the ceiling of a fire-resistance-rated corridor. Either a corridor damper or a ceiling radiation damper shall be installed depending upon the method of ceiling construction. As illustrated in Figure 717-4, an important exception eliminates the need for smoke dampers where steel ducts pass through, but do not serve, the corridor.

Figure 717-4   Ducts crossing corridor.

717.5.5   Smoke barriers. Those air openings, both ducts and transfer openings, that penetrate smoke barriers are to be provided with smoke dampers at the points of penetration. Steel ducts are permitted to pass through a smoke barrier without a damper, provided the openings in the ducts are limited to a single smoke compartment. Fire dampers are not required at penetrations of smoke barriers.

717.6   Horizontal assemblies.   The code is quite restrictive when it comes to the protection of vertical openings between floor levels, particularly where the floor or floor/ceiling assembly is required to be fire-resistance rated. This section requires the use of a shaft enclosure to address the hazard that is created where a duct or air transfer opening extends through a floor, floor/ceiling assembly, or ceiling membrane of a roof/ceiling assembly. The remainder of the section modifies this general requirement for through-penetrations, membrane penetrations, and nonfire-resistance-rated assemblies.

717.6.1   Through-penetrations.   Ducts and air transfer openings that penetrate horizontal assemblies are initially regulated by the provisions of Section 713 for shaft enclosures. Permitted in all occupancies other than Groups I-2 and I-3, a shaft enclosure is not required where a duct that connects only two stories is provided with a fire damper installed at the floor line of the fire-resistance-rated floor/ceiling assembly that is penetrated. As an option, the duct may be protected in a manner prescribed in Section 714.4 for the penetration of horizontal assemblies. The code’s intent to limit fire and smoke migration between smoke compartments vertically in Group I-2 and I-3 occupancies is maintained through the limitation imposed in this section. The exception goes on to eliminate the fire damper requirement as it relates to dwelling units and sleeping units, provided the duct penetrates no more than three floors.

717.6.2   Membrane penetrations.   A shaft enclosure need not be provided where an approved ceiling radiation damper is installed at the ceiling line of a fire-resistance-rated floor/ceiling or roof/ceiling assembly penetrated by a duct or air-transfer opening. Designed to protect the construction elements of the floor or roof assembly, the ceiling damper is not required where fire tests have shown that ceiling radiation dampers are not necessary to maintain the fire-resistance rating of the assembly. Additionally, ceiling radiation dampers are not required at penetrations of exhaust ducts, provided the penetrations are appropriately protected, the exhaust ducts are contained within wall cavities, and the ducts do not pass through adjacent dwelling units or tenant spaces.

717.6.3   Nonfire-resistance-rated floor assemblies.   The elimination of shaft enclosures at vertical openings is also possible where the floor assemblies are not required to be of fire-resistance-rated construction. Two conditions are identified using the filling of the annular space between the assembly and the penetrating duct with an approved noncombustible material that will resist the free passage of fire and smoke. Where only two stories are connected, no other protective measures are necessary. In three-story conditions, a fire damper must be installed at each floor line. The code also mandates that the floor assembly be of noncombustible construction and the annular space surrounding the penetrating duct be filled with an approved noncombustible material, such as a sealant, that will resist the free passage of flame, smoke, and gases. However, the installation of such sealant or other material would typically void the listing of the damper. Under such conditions, the use of the damper’s steel mounting angles would satisfy the intended purpose of the annular space protection. An exception permits this method of protection in a dwelling unit without the installation of a fire damper.

Section 718 Concealed Spaces

Fireblocking and draftstopping are required in combustible construction to cut off concealed draft openings (both vertical and horizontal). The code requires that fireblocking form an effective barrier between floors and between the top story and attic space. The code also requires that attic spaces be subdivided, as will be discussed later, along with concealed spaces within roof/ceiling and floor/ceiling assemblies. Figures 718-1 through 718-4 depict IBC requirements for fireblocking.

Figure 718-1   Fireblocking.

Figure 718-2   Fireblocks—vertical and horizontal space connections.

Figure 718-3   Fireblocks—stairs.

Figure 718-4   Fireblocks—pipes, chimneys, etc.

Experience has shown that some of the greatest damage occurs to conventional wood-framed buildings during a fire when the fire travels unimpeded through concealed draft openings. This often occurs before the fire department has an opportunity to control the fire, and greater damage is created as a result of the lack of fireblocking.

For these reasons, the code requires fireblocking and draftstopping to prevent the spread of fire through concealed combustible draft passageways. Virtually any concealed air space within a building will provide an open channel through which high-temperature air and gases will spread. Fire and hot gases will spread through concealed spaces between joists, between studs, within furred spaces, and through any other hidden channel that is not fireblocked.

718.2   Fireblocking.   The platform framing method that is used most often today in wood-frame construction provides adequate fireblocking between stories in the stud walls, but care must be exercised to ensure that furred spaces are effectively fireblocked to prevent transmission of fire and hot gases between stories or along a wall. For this reason, the code requires that fireblocking be provided at 10-foot (3,048-mm) intervals horizontally along walls that are either furred out, of double-wall construction, or of staggered-stud construction.

Fireblocking provisions for wood flooring used typically in gymnasiums, bowling alleys, dance floors, and similar uses containing concealed sleeper spaces are found in Section 718.2.7. As long as the wood flooring described in this section is in direct contact with a concrete or masonry fire-resistance-rated floor, there is no significant hazard. However, if there is a void between the wood flooring and the fire-resistance-rated floor, a blind space is created that is enclosed with combustible materials and provides a route for the undetected spread of fire. Therefore, the code requires that where the wood flooring is not in contact with the fire-resistance-rated floor, the space shall be filled with noncombustible material or shall be fireblocked. Two exceptions to these fireblocking requirements are:

1.   The first exception exempts slab-on-grade floors of gymnasiums. In this case, the code presumes a low hazard, as gymnasiums are usually only one story in height. If the floor is at or below grade, it is unlikely that any ignition sources would be present to start a fire that would spread through the blind space under the wood flooring.

2.   Bowling lanes are exempted from fireblocking except as described in the code, which provides for areas larger than 100 square feet (93 m²) between fire blocks. Fireblocking intermittently down a bowling lane would create problems for a consistent lane surface.

Fireblocking materials are required to consist of lumber or wood structural panels of the thicknesses specified, gypsum board, cement fiber board, mineral wool, glass fiber, or any other approved materials securely fastened in place.

Batts or blankets of mineral wool and glass fiber materials are allowed to be used as fireblocking and work especially well where parallel or staggered-stud walls are used. Loose-fill insulation should not be used as a fireblocking material unless specifically tested for such use. It must also be shown that it will remain in place under fire conditions. Even in the case where it fills an entire cavity, a hole knocked into the membrane enclosure for the cavity could allow the loose-fill insulation material to fall out, negating its function. Therefore, loose-fill insulation material shall not be used as a fireblock unless it has been properly tested to show that it can perform the intended function. The main concern is that the loose-fill material, even though it may perform adequately in a fire test to show sufficient fire-retardant characteristics to meet the intent of this section, would not be adequately evaluated for various applications because of the physical instability of the material in certain orientations.

718.3   Draftstopping in floors.   Draftstops are often used to subdivide large concealed spaces within floor/ceiling assemblies of combustible construction. Figure 718-5 shows IBC requirements for draftstopping in these locations. Gypsum board, wood structural panels, particleboard, mineral wool, or glass fiber batts and blankets, and other approved materials are considered satisfactory for the purpose of subdividing floor/ceiling areas, provided the materials are of adequate thickness, are adequately supported, and their integrity is maintained.

Figure 718-5   Draftstops—floors.

Draftstops are to be installed in floor/ceiling assemblies as follows:

1.   Residential occupancies. The code requires that draftstops be installed in line with the wall separating tenants or dwelling units from each other and the remainder of the building, consistent with the provisions of Section 718.3.2 for dwelling unit and sleeping unit separations. In this case, a fire originating in a dwelling unit or hotel room will find draftstops in the concealed space blocking the transmission of fire and hot gases into another hotel room or apartment. Where the residential occupancy is fully sprinklered, draftstopping is not required. Where a residential sprinkler system is used, automatic sprinklers must also be installed in the combustible concealed floor areas.

2.   All other occupancies. For uses other than residential occupancies, the code intends that the concealed space within the floor/ceiling assembly be separated by draftstopping so that the area of any concealed space does not exceed 1,000 square feet (93 m²). An exception permits the elimination of draftstopping where automatic fire sprinklers are installed throughout the building.

718.4   Draftstopping in attics.   In attics and concealed roof spaces of combustible construction, the code requires draftstopping under certain circumstances. Consistent with the requirements for fireblocking, draftstopping is not required for spaces constructed entirely of noncombustible materials. Materials used for draftstopping purposes, such as gypsum board, plywood, or particleboard, are to be installed consistent with the provisions of Section 718.3.1 for the draftstopping of floors. The following locations are identified as those requiring draftstopping:

1.   Groups R-1 and R-2. Draftstops are to be installed above and in line with the walls separating dwelling units or between walls separating sleeping units. Figure 718-6 explains the intent of Exception 1. Exception 3 applies to Group R-2 occupancies less than five stories in height. In this case, attic areas may be increased by installing draftstops to subdivide the attic into a maximum of 3,000-square-foot (279-m²) spaces, with no area to exceed the inclusion of two dwelling units. Exception 2 eliminates the need for draftstopping in fully sprinklered buildings, while Exception 4 considers the installation of a residential sprinkler system with sprinklers in the attic as an acceptable alternative to draftstopping.

2.   Other uses. Draftstops are required by the code to be installed in attics and similar concealed roof spaces of buildings other than Groups R-1 and R-2 so that the area between draftstops does not exceed 3,000 square feet (279 m²). As permitted by the exception, draftstopping of the attic space is not required in any building equipped throughout with an automatic sprinkler system. See Figure 718-7.

Figure 718-6   Attic draftstop—Groups R-1 and R-2.

Figure 718-7   Attic draftstop—other than Group R occupancies.

718.5   Combustibles in concealed spaces in Type I or II construction. Where buildings are intended to be classified as noncombustible, it is intended that combustibles not be permitted, particularly in concealed spaces. The six exceptions to this limitation identify conditions under which a limited amount of combustible materials is acceptable. Exception 1 references Section 603, which identifies 26 applications where combustible materials are permitted in buildings of Type I or Type II construction. It is felt that the low level of combustibles permitted, as well as their control, does not adversely impact the fire-severity potential caused by the combustible materials. Exception 2 permits the use of combustible materials in plenums under the limitations and conditions imposed by IMC Section 602. The third exception allows the concealment of interior finish materials having a flame-spread index of Class A. Exception 4 addresses combustible piping, provided it is located within partitions or enclosed shafts in a complying manner. As an example, the presence of plastic pipe within the wall construction of a Type I or II building does not cause the building to be considered combustible construction. Exception 5 allows for the installation of combustible piping within concealed ceiling areas of Type I and II buildings, while Exception 6 permits combustible insulation on pipe and tubing in all concealed spaces other than plenums.

Section 719 Fire-Resistance Requirements for Plaster

Where gypsum plaster or portland cement plaster is considered a portion of the required fire-resistance rating of an assembly, it must be in compliance with this section. Appropriate fire tests shall be referenced in determining the minimum required plaster thickness. It is important that the material under consideration is addressed in the test, unless the equivalency method of Section 719.2 is used.

In noncombustible buildings, it is necessary that all backing and support be of noncombustible materials. Except for solid plaster partitions or where otherwise determined by fire tests, it is also necessary in certain plaster applications to double the required reinforcement in order to provide for additional bonding, particularly under elevated temperatures. Under specific conditions, it is permissible to substitute plaster for concrete in determining the fire-resistance rating of the concrete element.

Section 720 Thermal- and Sound-Insulating Materials

The intent of this section is to establish code requirements for thermal and acoustical insulation located on or within building spaces. This section regulates all insulation except for foam-plastic insulation, which is regulated by Section 2603: duct insulation and insulation in plenums, which must comply with the requirements of the IMC; fiberboard insulation as regulated by Chapter 23; and reflective plastic core insulation, which must comply with Section 2613.

As a general requirement, insulation, including facings used as vapor retarders or as vapor permeable membranes, must have a flame spread index not in excess of 25 and a smoke-developed index not to exceed 450. Section 720.2.1 waives the flame-spread and smoke-developed limitations for facings on insulation installed in buildings of Type III, IV, and V construction, provided that the facing is installed behind and in substantial contact with the unexposed surface of the ceiling, floor, or wall finish.

Section 721 Prescriptive Fire Resistance

In this section, there are many prescriptive details for fire-resistance-rated construction, particularly those materials and assemblies listed in Table 721.1(1) for structural parts, Table 721.1(2) for walls and partitions, and Table 721.1(3) for floor and roof systems. For the most part, the listed items have been tested in accordance with the fire-resistance ratings indicated. In addition, a similar footnote to all of the tables allows the acceptance of generic assemblies that are listed in GA 600, the Gypsum Association’s Fire-Resistance Design Manual. It is important to review all of the applicable footnotes when using a material or assembly from one of the tables.

Section 721.1.1 intends that the required thickness of insulating material used to provide fire resistance to a structural member cannot be less than the dimension established by Table 721.1(1), except for permitted modifications. An example of the minimum thickness of concrete required for a structural-steel column is shown in Figure 721-1. Note that Figure 704-4 illustrates that the edges of such members are to be adequately reinforced in compliance with the provisions of Section 721.1.3. Figure 721-2 illustrates the minimum concrete-thickness requirements for protecting reinforcing steel in concrete columns, beams, girders, and trusses. Refer to Section 704 for additional provisions regarding structural members.

Figure 721-1   Prescriptive fire resistance.

Figure 721-2   Reinforcing steel in concrete columns, beams, girders, and trusses.

As previously mentioned, the fire-resistance ratings for the fire-resistance-rated walls and partitions outlined in Table 721.1(2) are based on actual tests. Figure 721-3 shows two samples from the table. For reinforced concrete walls, it is important to note the type of aggregate as discussed earlier in this chapter. The difference in aggregates is quite significant for a 4-hour fire-resistance-rated wall, as it amounts to a difference in thickness of almost 2 inches (51 mm). For hollow-unit masonry walls, the thickness required for a particular fire-endurance rating is the equivalent thickness as defined in Section 722.3.1 for concrete masonry and Section 722.4.1.1 for clay masonry. Figure 721-4 outlines the manner in which the equivalent thickness is determined.

Figure 721-3   Walls and partitions.

Figure 721-4   Equivalent thickness of masonry walls.

Table 721.1(3) of the IBC provides fire-resistance ratings for floor/ceiling and roof/ceiling assemblies, and Figure 721-5 depicts the construction of a 1-hour fire-resistance-rated wood floor or roof assembly. Of special note is Footnote n, which exempts unusable space from the flooring and ceiling requirements. See Figure 711-1.

Figure 721-5   One-hour wood floor or roof assembly item number 21-1.1.

Often, materials such as insulation are added to fire-resistance-rated assemblies. It is the intent of the IBC to require substantiating fire test data to show that when the materials are added, they do not reduce the required fire-endurance time period. As an example, adding insulation to a floor/ceiling assembly may change its capacity to dissipate heat and, particularly for noncombustible assemblies, the fire-resistance rating may be changed. Although the primary intent of the provision is to cover those cases where thermal insulation is added, the language is intentionally broad so that it applies to any material that might be added to the assembly.

721.1.5   Bonded prestressed concrete tendons.   Figure 721-6 depicts the requirements specified in Items 1 and 2 for variable concrete cover for tendons. It must be noted that for all cases of variable concrete cover, the average concrete cover for the tendons must not be less than the cover specified in IBC Table 721.1(1).

Figure 721-6   Variable protection of bonded prestressed tendons, multiple tendons.

As prestressed concrete members are designed in accordance with their ultimate-moment capacity, as well as with their performance at service loads, Item 3 provides two sets of criteria for variable concrete cover for the multiple tendons:

1.   Those tendons having less concrete cover than specified in Table 721.1(1) shall be considered to be furnishing only a reduced portion of the ultimate-moment capacity of the member, depending on the cross-sectional area of the member.

2.   No reduction is necessary for those tendons having reduced cover for the design of the member at service loads.

As the ultimate-moment capacity of the member is critical to the behavior of the member under fire conditions, the code requires the reduction for those tendons having cover less than that specified by the code. However, behavior at service loads is less affected by the heat of a fire; therefore, the code permits those tendons with reduced cover to be assumed as fully effective.

Section 722 Calculated Fire Resistance

Fire research and the theory of heat transmission have combined to make it possible with the present state-of-the-art technology to calculate the fire endurance for certain materials and assemblies. As a result of this testing and research, this section permits the calculation of the fire-resistance rating for assemblies of structural steel, reinforced concrete, wood, concrete masonry, and clay masonry.

At the present time, it is doubtful that the fire resistance of many buildings will be based on calculations. Even so, the code users should be aware of the useful information presented in this section, including: