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Both building codes and zoning ordinances are state (governmental) interventions that restrict the freedom of property owners. In the US context, such restrictive acts by the state have been controversial, but ultimately have been upheld by supreme court rulings over the years. The US constitution gives limited powers to the federal government; states then have the ability to impose building code and zoning restrictions.
In the recent past, many states had adopted their own building codes, many — but not all — based on "model codes" such as BOCA, or the UBC (Uniform Building Code), etc. These separate model code agencies have gotten together to produce a national model code, the International Building Code (IBC) which has been adopted by most if not all 50 states. This finally gives the US a de facto national code, even though each state may well modify it in its own way.
Zoning is still generally a municipal, county, or state function, and varies considerably from place to place. Where building codes cover issues like fire safety, accessibility, and structural safety, zoning generally deals with property limitations such as minimum property size, allowable property use (occupancies), building height, bulk, massing, floor-area-ratio, parking, setbacks (yards), and so on.
Watch this video to get a sense of the destructive power of fire, the speed with which it develops, and the incredible quantity of fuel supplied by ordinary domestic objects. Our discussion of fire safety is based on the IBC (International Building Code). Follow online links to "course readings" and "internet sources."
And yet is is still unusual for municipalities to require residential sprinklers in new construction: "'When you start mandating a fire sprinkler system, you are going to price a lot of people out of these new homes,' said Ned Munoz, vice president of regulatory affairs for the Texas Association of Home Builders, which lobbied heavily for anti-sprinkler legislation." (New homes burn faster, but states resist sprinklers) See this website for state-by-state data on residential sprinkler requirements.
How high (number of stories, height in feet)?
How much floor area (on one floor; on multiple floors)?
How far from property line, and how many windows?
What materials can it be constructed from?
How many means of egress (exits)? How wide?
How many "hours" fire-resistive rating on various elements?
Most answers determined as follows (IBC 2015):
Other specific questions are based on:
A = assembly
B = business (includes college buildings)
E = educational
F = factory and industrial
H = high hazard
I = institutional (nurseries, health care, jails)
M = mercantile
R = residential
S = storage
U = utility and miscellaneous
Type I and II basically non-combustible (steel and concrete framed)
Types III, IV, and V allow combustible materials
Type III previously called "ordinary construction"
Type IV previously called "heavy timber"
Type V is timber frame construction
See NYS 2015 Code for definition of the construction types (scroll down a bit).
See Table 601 (IBC 2006) for "fire-resistive rating requirements for building elements." This table tells you what a building of a certain construction type consists of:
nonbearing walls and partitions
For each element, the required fire-resistive rating (number of hours) is given.
See Table 602 (IBC 2015) for "fire-resistive rating requirements for exterior walls based on fire separation distance." This table tells you the required rating (number of hours) for exterior walls based on their distance (frontage) from the property line.
Graphic interpretation of exterior wall requirements:
See Table 508.4 (IBC 2015) for "required separation of occupancies (hours)." Tells you what kind of fire-rated wall must separate different occupancies within the same building.
See various tables in Chapter 5 (IBC 2015) for "allowable height and building areas." These are the most important tables for understanding how occupancy and construction type limit the allowable area and allowable heights in buildings. Excerpts from these tables are reproduced below (where NS = no sprinklers; S1 = sprinklered 1-story building; SM = sprinklered multi-story building; and UL = unlimited):
Allowable area per floor = Aa = At + (NS x If)
For all buildings, the maximum allowable area is equal to the allowable single floor area multiplied by the number of stories, up to three.
In any case, no single floor area can exceed the allowable single floor area.
Some exceptions for residential (Group R) buildings with NFPA 13R sprinklers (in such cases, for maximum 4-story buildings, the maximum allowable area can be taken as 4 x the allowable per-floor area).
Disclaimer: Students are responsible for material presented in class, and required material described on course outline. These notes are provided as a tentative outline of material intended to be presented in lectures only; they may not cover all material, and they may contain information not actually presented. Notes may be updated each year, and may or may not apply to non-current versions of course.
first posted Aug. 28, 2012 | last updated: Aug. 29, 2017
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