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ARCH 2614/5614 Lecture notes

Jonathan Ochshorn

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Construction types and occupancy

Overview of building codes and zoning ordinances:

Fire safety per building code:

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.

Introduction: Building code fire safety issues

  1. How high (number of stories, height in feet)?

  2. How much floor area (on one floor; on multiple floors)?

  3. How far from property line, and how many windows?

  4. What materials can it be constructed from?

  5. How many means of egress (exits)? How wide?

  6. How many "hours" fire-resistive rating on various elements?

Most answers determined as follows (IBC 2015):

  1. Occupancy group: chapter 3
  2. Construction type: Table 601

Other specific questions are based on:

  1. Exterior wall openings: Table 602
  2. Separation of mixed occupancies: Table 508.4
  3. Heights and areas: Various tables in chapter 5

Occupancies (chapter 3):

See NYS 2015 Code example.

Construction type:

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:

For each element, the required fire-resistive rating (number of hours) is given.

See NYS 2015 Code example.

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:
graphic depiction of walls and window openings allowed

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.

Table 508.4, 2015 IBC

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):

Tables from Chapter 5, 2015 IBC

See NYS 2015 Code example.

Allowable area per floor

Allowable area per floor = Aa = At + (NS x If)

where

Total allowable building area

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).

diagram showing total allowable building area
In each case illustrated above, the maximum allowable per-floor area is "A." The allowable total building area cannot exceed 3 x A, and any given floor cannot exceed "A"