2 NAVIGATING THE CODE.pdf

2 Navigating the Code The key word to remember about how all building codes are developed and how they all work is intent. 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 spe...

2 Navigating the Code The key word to remember about how all building codes are developed and how they all work is intent. 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. The application of the code requires interpretation on the part of designers and the Authorities Having Jurisdiction [AHJ]. The individual’s view of intent can lead to alternative interpretations of code compliance. One of the goals of resolving an unfavorable code interpretation is to convince the AHJ that the proposed design meets the intent of the writer of the code section in question and thus complies with the code. Note that in the 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. IBC Definition Code section using the definition (in italic type) 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. intent + interpretation = • intent • intent • intent 10 / BUILDING CODES ILLUSTRATED—THE BASICS 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 keyword searches. Don’t try and memorize passages of the code, because these may change or move around inside the code over time or in various jurisdictions 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 keyword 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, solid vertical lines [ ] in the margins indicate a text change from the previous 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 consider getting 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. INTENT AND INTERPRETATION 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, mixeduse 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. ”An alternative material, design or method of construction shall be approved where the building official finds that the proposed alternative meets all of the following: 1. The alternative material, design, or method of construction is satisfactory and complies with the intent of the provisions of this code. 2. The material, method or work offered is, for the purpose intended, not less than the equivalent of that prescribed in this code as it pertains to the following: • Concrete, spray-on fireproofing, or gypsum board provide alternate means of fireproofing a structural steel member. 2.1. Quality 2.2. Strength 2.3. Effectiveness 2.4. Fire resistance 2.5. Durability 2.6. Safety” The list of words above are also the fundamental criteria for why each and every code section is included in the basic code. NAVIGATING THE CODE / 11 INTENT AND INTERPRETATION 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 aware 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. Also, 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. 12 / BUILDING CODES ILLUSTRATED—THE BASICS • Visualize code problem. • Read relevant code sections. • Interpret intent of code. • Revisualize possible solution that satisfies both design intent and intent of the code. INTENT AND INTERPRETATION 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 the start of every code analysis, research should be undertaken to determine what, if any, local code amendments are applicable to a project. 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 Occupancy Classification Fire Protection (active) Building Height (feet/stories) Building Area Type of Construction Means of Egress Allowed per Code Select from Chapter 3 Select per occupancy Allowed per proposed type Select per construction type Determine from design Select per occupancy A site plan and floor plan should be included that describe the location of the building on the property and any height, area, or construction-type credits or requirements related to location on the site and proximity to streets and other structures. The floor plan should also detail egress requirements, such as exit access widths, exit quantities and locations, and exit discharge paths to the public way. A recommended code room tag is shown below. #### Room Name Occupancy Group Area—SF Room Number Assigned Room Use Per IBC Chapter 3 “Gross” or “Net” per IBC Chapter 2 Occ. Load Factor Per IBC Table 1004.5 # of Occupants Area/OLF Door Width Width of required door(s) at least 32" (813) clear. • Occupancy classification • Location of building on property • Relationships between multiple buildings on one site • Building area • Construction type PUBLIC WAY Code Section or Table Chapter 3 Chapter 9 Tables 504.3 and 504.4 Table 506.2, as adjusted Chapters 5, 6, 7 Chapter 10 • Exit access widths • Exit locations and quantities • Exit discharge paths to a public way • Building height in stories/feet 4 3 2 1 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. 5 4 3 2 1 With these pieces of information, it is possible to determine how the code prescribes the minimum for: • Construction type—determined by calculation for allowable areas and heights. • Exit locations and quantities. • Exit access widths. • Exit discharge to a public way. NAVIGATING THE CODE / 13 USING THE CODE The following procedure is recommended as being helpful in using the International Building Code and any applicable local jurisdiction code amendments. Note that most of the major issues are interactive and that iteration of relationships will almost certainly be required to optimize design solutions and steps may not occur in precisely the same order for each iteration. The procedure can be paraphrased as follows. 1. Classify the building according to occupancy, type of construction, location on property, floor area, height, and number of stories. A. Occupancy Classification Determine the occupancy group that the use of the building or portion thereof most nearly resembles. Compute the floor area and occupant load of the building or portion thereof. See the appropriate sections in Chapter 5 for requirements for buildings with mixed occupancies. B. Sprinkler Systems C. Type of Construction Determine if the occupancy is Determine the required required to be protected by a minimum type of construction, sprinkler system and identify the or architecturally desired threshold(s). Determine if the construction type, based on the anticipated height of the building occupancy, fire protection, and will require fire sprinklers. See the designed height and area. the appropriate sections in This will dictate the materials Chapter 9 for thresholds based used and the fire resistance on the occupancy. Note also of the parts of the building as the sprinkler adjustments for limited in Chapter 6. heights and areas in Chapter 5 as described in Step “D.” The basic model IBC requires sprinklers in many conditions. Local amendments are often made to either increase or decrease sprinkler thresholds and requirements. 14 / BUILDING CODES ILLUSTRATED—THE BASICS D. Allowable Floor Area Determine the allowable floor area of the building. Use the basic allowable floor area based on occupancy group and type of construction. Determine allowable floor area of multistory buildings. Determine allowable increases based on location on property and if there is installation of an approved automatic firesprinkler system. USING THE CODE 2. Review requirements for firesprinkler protection. H 3. Review the building for conformity with the type-ofconstruction requirements in relation to desired and allowable building heights and plan areas. Iteration may be required among heights, areas, and construction types. 4. Review the effects on the building based on its location on the building site. Iteration may be required in reviewing location together with construction types and amount of openings in relation to property lines. E. Height and Number of Stories Compute the height of the building and determine the number of stories. Determine the maximum height and number of stories permitted based on occupancy group and type of construction. Determine allowable height and story increase based on the installation of an approved automatic fire-sprinkler system. F. Location on Property Determine the location of the building on the site and clearances to lot lines and other buildings from the plot plan. Determine the fire-resistance requirements for exterior walls and wall-opening requirements based on fire-separation distances to lot lines. The fireresistance requirements for exterior walls and the limitations on their openings are found in Chapter 7. G. Means of Egress Determine the requirements for means of egress from the building found in Chapter 10. 5. Review the building for conformity with egress requirements. 6. Review the building for other detailed code requirements. 7. Review the building for conformity with structural engineering regulations and requirements for materials of construction. NAVIGATING THE CODE / 15 CODE COMPONENTS 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 tradeoffs 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. 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 I II III • Increasing fire resistance and cost The following section is a review of the critical information required for a project code analysis, based on the analysis system noted above. IV V • Decreasing number of occupants and cost 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 fireresistant construction types are allowed to be of larger area and to have more stories as the fireresistance 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. 16 / BUILDING CODES ILLUSTRATED—THE BASICS 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 appropriate 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. CODE COMPONENTS Passive fire protection 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. Shaft 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. Active fire protection 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. 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. Fire-resistance standards include: 1. 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. 2. Area or Occupancy Separation Rating: Requirements of how long it will take for a fire to penetrate a wall partition, floor, or roof assembly. 3. 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. NAVIGATING THE CODE / 17 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 previously, be sure to do research about local code amendments to the model code. As noted, don’t be shy about using the table of contents, index, or keyword searches of electronic documents. 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. 18 / BUILDING CODES ILLUSTRATED—THE BASICS