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Lecture notes
Department of Architecture, Cornell University

ARCH 2614/5614 Building Technology I: Materials and Methods

Jonathan Ochshorn

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Fire safety overview, sprinklers, fire areas, construction types and occupancy

Introduction

Proposition: Many important things about architecture are in motion.

A. Historical context.

1. Urban conflagrations were common, devastating entire sections of cities.

2. Trend in fire safety strategy has been shift from limiting fire to:

B. Concerns.

1. life safety

2. protection of property


graphic showing thermal vs. non-thermal impact

C. Strategies.

1. alert occupants (fire detecting devices, call boxes, alarms). Based on smoke or heat.

2. provide protected means of egress.

3. compartmentation: provide barriers to keep fire isolated. Concept shows up in numerous ways, at different scales:

4. ventilation: vent smoke, toxic gases.

Windows, skylights, mechanical equipment, roof hatches, etc.

5. Suppression:

6. site planning issues:

Some images and videos:

But can real architecture catch on fire?

2015 fire, 50th floor Hancock Tower in Chicago
Fire on 50th floor of the John Hancock Building in Chicago (S.O.M. architects), 2015


Construction types and occupancy

Overview of building codes and zoning ordinances:

Fire safety per building code:

Watch this 6-minute 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" or just go directly here.

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 2018):

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

Other specific questions are based on:

  1. Exterior wall fire-resistive ratings and openings: Table 602 and Table 705.8.
  2. Separation of mixed occupancies: Table 508.4
  3. Heights and areas: Various tables in chapter 5

Occupancies (chapter 3):

See NYS 2020 Building Code (based on 2018 IBC), Chapter 3.

Construction type:

See NYS 2020 Building Code (based on 2018 IBC), Chapter 6 for definition of the construction types (scroll down a bit to Section 602.2, 602.3, 602.4, and 602.5).

Building elements corresponding to construction types:

See Table 601 NYS 2020 Building Code (based on IBC 2018) 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.

Table 601 from 2018 IBC
Table 601 footnotes are not shown; see IBC for complete details.


Exterior wall fire-resistance based on distance from property line:

See Table 602 NYS 2020 Building Code (based on IBC 2018) 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. See Table 705.8 for percentages of allowable openings in exterior walls.

Graphic interpretation of exterior wall requirements:
graphic depiction of walls and window openings allowed

Table 602 from NYS 2020 Building Code (based on 2018 IBC)
Table 602 footnotes are not shown; see IBC for complete details.