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2
Navigating the Code

The key word to remember about how all building codes are developed and how they all work is intent. As we noted in the Preface, code sections have individual authors who had some problem in mind when they wrote a code-change proposal. The intent of the author of a building-code section is to solve a specific design problem with prescriptive language. Designers are usually trying to measure visual and spatial expressions against the language of the code. During this process, the designer should ask what problem or performance criteria the code section is addressing. The language will start to make more sense as one tries to go beyond the specific language to determine why the words say what they say.

Designers also have intent. They are trying to achieve certain functional or formal goals in the design of the building. Designers should measure their own intent for the design against their interpretations of the intent of the code. When examined together, the intent of the code and that of the design solution should be concurrent.

Do not try and ignore the code. Do not try and obfuscate code issues to achieve approvals. The responsibility for understanding, applying, and fulfilling the requirements of the code always rests with the design professional. Approvals by the AHJ do not relieve the designer of social and licensing responsibilities to maintain the health, safety, and welfare of society.

Intent and Interpretation

Each section of the code was developed to solve a certain problem. Code sections are typically written in relatively short paragraphs. Sections are organized into chapters based on common themes, but sections may be developed in isolation from one another with little attention to continuity of the entire document. As you look at the code, try and visualize the intent of the writer of that section and try to understand the problem they were addressing. Code language usually arises from a specific issue the code writer wishes to address based on experience or on an actual construction or life safety issue. The writer then makes the requirements general so that they will apply to more typical conditions than the specific instance that generated the concern.

The intent of the code is a crucial idea to understand. Why is a much more important question than what when you are puzzled by the actual language of a code passage. The code is a general document that must then be interpreted for its specific application to a specific project. If you know the code in general and think about its intent, you will be in a better position to formulate your own interpretation of code sections as they apply to your specific project. You will thus be in a position to help building officials see the validity of your opinion when interpretation of the code is required for a specific design condition. Confidence will come with experience in use of the code. Learning the code is vital to your success as a well-rounded designer.

Note that in the 2018 IBC certain terms are in italic type. These italicized terms appear in the definitions in Chapter 2. Where terms are used in ways intended by their definitions they are italicized in the body of the code. Italicized type is not used in this book in the same way. The code publisher's intent for this notification method is to highlight for the code user that the code's definitions should be read carefully to facilitate better understanding of how they are used in the context where they appear in italics. It is critical that the code user go back to the code definitions when attempting to understand the literal and figurative meaning of code requirements. When attempting to interpret a code section, be sure to examine the code definitions for the terms used in the code section. Do not assume that the meanings of terms are the same as in everyday speech, especially for italicized text.

While definitions occur in the IBC in Chapter 2, this book discusses definitions in context with where the defined items are used in the technical requirements in the code. We believe this makes the analysis in this book easier to follow. Defined terms from the IBC are noted in [bracketed italic type]. Thus defined terms will be found throughout the various chapters of this book. Prior editions of the code listed definitions to be found in Chapter 2. This edition has deleted those references, completing the move of definitions wholly to Chapter 2.

Learn the table of contents and use the index. It is very useful to get the code in electronic form for use in your practice. This allows key word searches. Don't try and memorize passages of the code, because these may change or move around inside the code over time as the code is amended. Learn the organization of the code and learn where to find things that way. Use the index if the table of contents doesn't get you where you want to be. Think of synonyms for the topic you are researching to facilitate key word or index searches. You may have to scan large portions of the index to locate potential items. Try to remember associations of ideas, not specific language, to facilitate your use of the code.

In the code, blue and green text indicate a text change from the 2012 code edition. There will be an arrow in the margin [—>] indicating a deletion in the section. A single asterisk [*] placed in the margin indicates that text or a table has been relocated within the code. A double asterisk [**] placed in the margin indicates that the text or table immediately following it has been relocated there from elsewhere in the code.

You should probably own a personal printed copy of the model code, and an electronic copy as well. Remember that the model code is often amended during adoption by local agencies. Be certain to find out what local code amendments to the code apply to your specific project. Also determine if the local AHJ has published written opinions regarding their interpretation of the code in their jurisdiction.

Alternative Means and Methods

§ 104.11 states that the provisions of this code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code. While written around prescriptive descriptions of tested assemblies and rated construction, the code recognizes that there may be many different ways of solving the same design problems. It recognizes that there will be innovations in building types, such as covered malls, mixed-use buildings, and atrium buildings that do not fit neatly into prescribed occupancy classifications. The code also recognizes that there will be innovations in materials and construction technology that may happen faster than code revisions are made. Thus the code sets up a method for the building official to approve proposed alternative designs. Deviations from prescribed standards must be submitted for review and approval of the building official. The criteria they are to use are spelled out in the code. We have highlighted some of the key provisions of the approval in bold italics. The alternative is to be approved when “the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method, or work offered is, for the purpose intended, not less than the equivalent of that prescribed in the code in quality, strength, effectiveness, fire resistance, durability, and safety” (emphasis added). These words are also the fundamental criteria for why each and every code section is included in the basic code.

Evaluation of Innovative Products

Innovations in construction materials and methods need to be evaluated for code compliance. Testing agencies often perform standardized tests on new products. These tests and data about the product must then be evaluated for code compliance. One popular way of demonstrating compliance to the AHJ for products or construction methods is through the use of ICC Evaluation Service reports.

ICC-ES is a nonprofit, limited liability company that does technical evaluations of building products, components, methods, and materials. Reports are prepared at the request of companies wishing their products to be evaluated by ICC-ES. Supporting data, such as product information and test reports, is reviewed by the ICC-ES technical staff for code compliance. The evaluation process culminates with the issuance of a report on code compliance. The reports are public documents, readily available on the Internet. They may be used by designers in determining whether an innovative or unusual construction material or process is code-compliant. The designer may then use the ICC-ES report to demonstrate code compliance by submitting it for review by the AHJ.

Code Interpretations

Designers and code officials approach interpretations from quite different perspectives. The designer is trying to make a functional or formal design code compliant while satisfying project requirements in an aesthetic, economical, and practical way. The AHJ examines completed drawings for compliance with code requirements. While the AHJ is not unaware of the practical requirements contained in the building design, they are charged first and foremost with protecting the health, safety, and welfare of the public by verifying code compliance. It is the responsibility of the designer to demonstrate code compliance and to modify noncompliant areas identified during plan review by the AHJ while continuing to meet the project requirements.

Both the designer and the AHJ are working to apply generalized code provisions to a specific project. It is differences in opinion about the application of the general to the specific that most often give rise to differences in interpretation. Code officials also see many more similar examples of the relationship of code sections to various designs. Thus they may generalize interpretations from one project to another even though the projects may be different in significant ways. On the other hand, designers may find that similar designs receive quite different interpretations by the AHJ in different jurisdictions. When differences of opinion about interpretation occur, the designer must work with the AHJ to reconcile the intent of the design to the interpretations of the intent of the code. If reconciliation cannot be reached, the designer must decide whether to revise the project to obtain approval or appeal the ruling of the AHJ to some civic body prescribed in the jurisdiction for hearing appeals. Often the AHJ can be requested to apply to the model-code agency that published the code for a ruling as to the publisher's opinion of the intent of the code section in question. Such appeals to the ICC are allowed to be made by any ICC member. It is thus prudent for design professionals to be ICC members to be able to access this service. In addition members receive discounts on ICC codes and have access to other interpretive and educational materials. Members may also participate in the code development process and gain deeper insights into code interpretations.

Documenting Code Interpretations

Every project should receive a detailed code analysis that is recorded as a permanent part of the permit documents. All code interpretations and citations should have a reference to the code section in question to allow retracing steps in the code analysis. Without a code section citation it is very difficult to have a productive discussion about interpretations. Recording citations focuses code issues for the designer during the design process and facilitates plan reviews by the AHJ.

At minimum the analysis should contain the following items. We recommend the following format to unify code analysis for all projects. The code section citations used should be specific for the project and sections, not as limited as in our example.

Proposed Condition	Allowed per Code	Code Section or Table
Occupancy Classification	Select from Chapter 3	Chapter 3
Fire Protection (active)	Select per occupancy	Chapter 9
Building Height (feet/stories)	Allowed per proposed type	Tables 504.3 and 504.4
Building Area	Select per construction type	Table 506.2, as adjusted
Type of Construction	Determine from design	Chapters 5, 6, 7
Means of Egress	Select per occupancy	Chapter 10

Figure depicts the coding of a building including occupancy classification, location of building on property, relationships between multiple buildings on one site, building area, exit locations and quantities, and exit discharge paths to a public way.

Figure lists building height in stories/feet.

For the designer, many elements required to determine how the code should apply to a project are a given from the program and the site or zoning constraints:

Occupancy classification—the client determines what functions they want;
Location of building on property—determined by the building footprint, zoning, natural features, etc.;
Building height and area—given the scope of the project, the designer will note how large the building needs to be and how many floors will be required.

With these pieces of information it is possible to determine how the code prescribes the minimum for:

Construction type—determined by calculation;
Exit locations and quantities;
Exit access widths;
Exit discharge to a public way.

Using the Code

The following procedure is recommended as being helpful in using the International Building Code. Note that most of the major issues are interactive and that iteration of relationships will be required to optimize design solutions. The procedure can be paraphrased as follows.

Figure depicts occupancy classification.

Code Components

The following section is a review of the critical information required for a project code analysis, based on the analysis system noted above.

Occupancy Type

Projects are almost invariably defined for the designer based on occupancy type. A client almost always comes to a designer with a defined need for a facility. The use of that facility determines the occupancy classification to which it belongs. Each occupancy classification or type has specific requirements related to allowable area, height, and exiting, with potential construction types growing out of these requirements. The codes are fundamentally use (occupancy) based. Other criteria are derived from the first basic classification by occupancy. Occupancy classifications are defined in Chapter 3.

Fire Extinguishing Systems

Fire sprinklers, standpipes, fire detection, and fire-alarm systems are an integral part of most new buildings. Use of such systems, especially automatic fire sprinklers, often results in trade-offs for additional height or area. Trade-offs are listed in the code sections related to height and areas, but other requirements are listed in separate sections of the code. Fire-protection systems are covered in Chapter 9. Note also that sprinkler system requirements are another area where local amendments are often added to the model codes. These requirements should be verified for each project. It can be critical to a trade-off to know if a system is otherwise required in the jurisdiction where you are working, as it may remove the model-code option of using some items like a sprinkler trade-off in lieu of fire rating certain parts of the building structure. Trade-offs only apply when the systems are not otherwise required by the local code to be used for a project. The idea of a trade-off recognizes that this is a mitigation measure over and above basic code requirements to achieve the desired level of safety through other means than those spelled out in the basic code.

Construction Type

Construction types are typically categorized by materials based on their resistance to fire in structural applications. The construction type gives some indication of the amount of time available for evacuation of occupants, for firefighting, and for emergency response under fire conditions. Buildings of fire-protected steel or concrete will provide more fire resistance than those of wood construction. More fire-resistant construction types are allowed to be of larger area and to have more stories as the fire-resistance increases. As a rough rule of thumb, allowable occupancy quantities and construction costs will both decrease with building type from Type I to Type V.

Types of construction are defined in Chapter 6. Table 601 gives a synopsis of the minimum fire-resistive requirements of each main element of building construction. As you go through a code analysis, you will be referring to this table and to Table 506.2 to select the optimum balance of construction type, occupancy, and area requirements for a specific project. It is typically a budget goal to minimize construction costs by selecting the least costly construction type appropriate for the proposed use of the building.

Figure depicts the water showered on the flame.

Building or Floor Area

Once the occupancy classification and construction type are known, it is important to establish the permissible area for each floor, for each use, and for the total building. Certain types of construction are limited in size based on occupancy and concentration of people. As noted, selection of the allowable area and construction type may require iteration of selections of construction type and allowable area based on occupancy requirements.

Allowable areas are tabulated in Table 506.2. See § 506 for allowable area increases based on location on the property and allowance for installation of automatic fire-sprinkler systems.

Building Height

The allowable number of floors is tied closely to construction and occupancy classification. Total height in feet and number of stories may also be limited by planning codes, not for technical reasons but as matters of public policy.

Building heights are tabulated in Tables 504.3 and 504.4. Study the definition of height and story as noted in the IBC. Also be aware that the definition of height and story is often subject to local amendment. Be certain to check these provisions with the local AHJ to be certain of the exact requirements for your project. This is especially true in older, hilly cities like San Francisco, where topography and historical development patterns may generate definitions of height or story different than in other jurisdictions. Do not confuse zoning height definitions and limits with those in the building code. They are usually different in almost all jurisdictions.

Exits/Egress

One of the most important functions of building codes is determining egress requirements and provision of safe means of egress for all of the anticipated occupants of a building. There are specific requirements for size, spacing, and travel distances for all components of the means of egress, such as floor plans, doors, corridors, and stairs. In simple terms, a means of egress consists of three components: an exit access, an exit, and an exit discharge. Chapter 10 of the IBC relates to means of egress.

Building Separations and Shafts

Where buildings have mixed occupancies, designers have the option of selecting separated occupancies, which require fire-rated partitions to separate the occupancies, or using “nonseparated” occupancies. Separations may also be used to allow more area for a particular occupancy on a single floor in certain types of construction where such sizes of use would not otherwise be permitted.

Openings between floors such as for stairs, elevators, and mechanical shafts can allow the passage of smoke, heat, and flames in a fire. Therefore the codes have requirements based on occupancy, building type, and building height related to shaft protection. Basic shaft-protection requirements are contained in Chapter 7.

Figure depicts the shaft position in a building's map.

Fire Protection

Fire protection can be divided into two broad categories: passive or active protection. Passive protection is that built into the structure, either inherent in the material or added as part of protective membranes. Thus a steel building has more inherent passive protection capability than a wood one because steel is noncombustible whereas wood is not. Active systems are ones where a fire causes a reaction in a system that serves to combat the fire. Sprinklers are a prime example of active systems. A fire causes a sprinkler system to activate and extinguish the fire before exposing the passive systems to a fire. Code analysis and design often includes trade-offs between active and passive systems.

Fire-resistance standards include:

Structure Hour Rating: Requirements for the time it takes for a fire to weaken a structural element to the point of failure. These requirements are minimums based on providing enough time for firefighting and evacuation operations to take place for a specified time period without placing emergency responders and occupants in danger.
Area or Occupancy Separation Rating: Requirements of how long it will take for a fire to penetrate a wall partition, floor, or roof assembly.
Flame Spread and Smoke Generation: Requirements of how long it takes for fire to move along the surface of a building material and how much smoke is generated under fire exposure. The density and toxicity of the smoke is also a factor to be considered in these criteria.

Fire-resistance requirements are found primarily in Chapters 7 and 8.

Engineering Requirements

A large portion of the code is devoted to engineering requirements. One of the bases of codes is structural adequacy of buildings for both static loading such as occupants and equipment, and dynamic loading such as earthquakes, snow, and wind. Requirements for both structural systems and structural materials are contained in the code. Chapters 16–18 deal with forces, inspections, and foundations. Chapters 19–23 deal with structural materials: concrete, lightweight metals, masonry, steel, and wood.

Code Analysis

Every project, no matter how small, should have a written code analysis included in the construction documents. We recommend organizing the code analysis in the same order as shown earlier in this chapter, so that the thought process you use in developing your code conclusions is revealed in the written code analysis. This should be done early in the design process so that any issues can be identified and discussed with the Authorities Having Jurisdiction.

As noted, don't be shy about using the table of contents and index to locate sections of the code. DO NOT TRY AND MEMORIZE PARTS OF THE CODE! As sections change and interpretations alter meanings, memorization is a recipe for trouble in the future. Clients may expect you to be able to rattle off requirements at a moment's notice, but it is not in the best interest of the project or the client to be able to make snap code decisions. Remember where to look up information and check your decisions each time you apply them; do not proceed on memory or analogy from other jobs. Even seasoned code professionals use the index or an electronic code to locate familiar phrases when they cannot quite recall where the phrase is located in the code. It is worthwhile for designers to remember that as a new model code edition is adopted across the nation, local code officials will often have little more hands-on experience with the IBC than design professionals.

Early Meetings

One advantage of larger projects is that they are often large enough to warrant pre-review and consultation with the building department prior to finalizing design. No matter what the size of your project, we recommend consulting with the applicable AHJ early in the process wherever it is possible, prior to commencing detailed design, even if a fee is charged. We also recommend that both the building and fire plan reviewers be at such meetings as they often do not always interpret the building and fire codes in the same way.

Do not expect the code official to do your work for you. Compliance is the responsibility of the designer. However, codes are subject to interpretation, and it is almost always in your best interest to determine what, if any, interpretations will be needed for any project. This should be done prior to expending a lot of time and energy designing a project that may be deemed not in compliance during plan review.