Fire resistance is determined by a building material's ability to withstand fire conditions. It is most commonly tested by subjecting structural components to standardized fire tests and rating the length of time until failure. Building codes classify construction types based on materials used and required structural fire resistance for safety. Occupancy classifications group buildings by similar fire risks to determine construction requirements.

1. Building Construction
Related to the Fire Service
Chapter 2 — Structural Fire
Resistance and Building
Classifications

2. Learning Objective 1
Define fire resistance.
Building Construction
2–2

3. Fire Resistance
• Function of the properties of all
materials used; includes combustibility,
thermal conductivity, chemical
composition, density, and dimensions
• Ability of a structural assembly to
maintain load-bearing and structural
integrity under fire conditions
(Continued)
Building Construction
2–3

4. Fire Resistance
• Ability of walls, partitions, and ceilings
to act as a fire barrier
• Fire resistance rating
– Expressed in hours and fractions of hours
– Incorporated into construction
classifications and building codes
Building Construction
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5. Learning Objective 2
Discuss methods of determining fire
resistance and the limitations of each
method.
Building Construction
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6. Determination of Fire
Resistance
• Conducting standard fire resistance
testing in a laboratory
• Performing analytical calculations to
determine the resistance to a standard
fire test exposure
• Employing analytical structural fire
engineering design methods based on
real fire exposure characteristics
Building Construction
2–6

7. Fire Resistance Test Method
• Laboratory test is most commonly used
method
• Component subject to heat of a
standard fire in test furnace
• Primary points of failure for test
• Fire resistance ratings expressed in
standard intervals
(Continued)
Building Construction
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8. Fire Resistance Test Method
• Factors impacting fire resistance ratings
from standard test
• Standard fire test evaluates ability of
structural assemblies to carry a
structural load and act as a fire barrier
• Information NOT provided by test
• Assemblies may be penetrated
(Continued)
Building Construction
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9. Fire Resistance Test Method
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10. Learning Objective 3
Identify fire testing organizations and
discuss the significance of fire test
results.
Building Construction
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11. Fire Testing Organizations
• Testing for fire resistance ratings is
beyond capability of local fire and
building departments
• Several laboratories are equipped to
conduct testing
• Some organizations use furnaces
primarily for research and product
development
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12. Fire Test Results
• Published by testing
laboratories
• Deviation from
materials or
dimensions specified
alters test results
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13. Learning Objective 4
Recognize the role of analysis in
determining fire resistance.
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14. Analytical Calculation of
Fire Resistance
• Mathematical equations have been
developed to predict behavior of
materials under test conditions
• ASCE/SFPE 29 provides methods for
calculating fire resistance ratings
• Limited to use with certain materials
Building Construction
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15. Analytical Design Using
Real Fire Exposures
• NFPA® 251 test
– Most commonly used
– May be too severe or not severe enough
• Ratings determined analytically using a
different time-temperature curve must
be interpreted cautiously
Building Construction
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16. Noncombustible Materials
• Building codes contain explicit criteria
for determining combustible material
• Incapable of supporting combustion
under normal circumstances
• Most common test for determining
combustibility – ASTM E 136
Building Construction
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17. Learning Objective 5
Discuss the basic building
classifications as they relate to fire
resistance.
Building Construction
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18. Classifications
• Type I, Fire-Resistive
• Type II, Noncombustible or protected
noncombustible
• Type III, Exterior protected
• Type IV, Heavy timber
• Type V, Wood frame
(Continued)
Building Construction
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19. Classifications
• In building codes, based on materials
used in construction and hourly fire
resistance ratings required for structural
components
Building Construction
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20. NFPA ® 220
• Details requirements for each classification
and subclassification
• Designated by three-digit number code
– 1st – Fire resistance rating in hours of exterior
bearing walls
– 2nd – Fire resistance rating of structural frames
or columns and girders supporting loads
greater than one floor
– 3rd – Fire resistance rating of floor construction
Building Construction
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21. International Building Code ®
(IBC ® )
• Similar to NFPA® 220
• Requirements for individual structural
members differ
• Building codes use construction types
and occupancy in conjunction with
sprinkler systems and separations to
establish limits on heights and areas of
buildings
Building Construction
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22. Type I Construction
• Structural members
are noncombustible
construction with a
specified fire
resistance Courtesy of McKinney (TX) Fire Department
• Combustible material typically permitted
in certain components
• Most common methods of construction
Building Construction
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23. Type II Construction
• Noncombustible – Can be either
protected or unprotected
• IBC® divides into two subclassifications
• Material other than steel can be used
• Building codes allow combustible
material similar to that in Type I
(Continued)
Building Construction
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24. Type II Construction
• Unprotected, noncombustible building
cannot be expected to provide
structural stability under fire conditions
• Point at which unprotected members
will fail depends on several factors
• Protected, noncombustible structural
fire protection is similar to Type I
Building Construction
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25. Type III Construction
• “Ordinary construction”
• Exterior walls frequently masonry, but
can be any noncombustible material
with required fire resistance
• Interior members
– Partially or wholly combustible
– Protected or unprotected
(Continued)
Building Construction
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26. Type III Construction
• IBC® divides into two subclassifications
• When fire resistance is required, most
common is plaster (older) or gypsum
board (newer)
• Wood dimensions permitted to be
smaller than Type IV
• Fundamental fire concern – Concealed
spaces
Building Construction
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27. Type IV Construction
• “Mill construction”
• Difference from Type III
• Used in older factories,
mills, and warehouses
• Primary fire hazard –
Massive amount of fuel Courtesy of McKinney (TX) Fire Department
from large structural
members
Building Construction
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28. Type V Construction
• All structural components
may be combustible
• Two subclassifications
• Differences from Type III
• Threat to adjacent
structures if heavily
involved in fire
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29. Mixed Construction
• Some buildings are allowed a mixed
construction type
• May result in special challenges for
emergency responders
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30. Learning Objective 6
Discuss the concept of fire load and its
impact on building construction types.
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31. Fire Load
• Maximum heat released if all available
fuel in a building was consumed
• Product of weight of combustibles
multiplied by their heat of combustion
• Expressed in lb/sq ft (kg/sq m)
• Varies depending on heat of
combustion of fuel
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32. Fire Load and Construction
Type
• Buildings with combustible structural
components have greater fire load than
Type I and II
• Fire load does not translate into
equivalent structural load
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33. Learning Objective 7
Explain occupancy classifications as
they relate to fire risks.
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34. Occupancy Classifications
• Assign building occupancies into
groups with broadly similar fire risks
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35. IBC ® Classifications
• Group A – Assembly • Group I – Institutional
• Group B – Business • Group M – Mercantile
• Group E – Education • Group R – Residential
• Group F – Factories • Group S – Storage
• Group H – High • Group U – Utility and
Hazard Misc.
Building Construction
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36. International Building Code ®
• Considerable variation of hazards within
groups, so further divided to describe
occupancy groups with more similar
characteristics
• Total of 26 subgroups
• Separate provision for one- and two-
family dwellings not more than three
stories high
Building Construction
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37. NFPA ® Classifications
• Assembly • Residential
• Educational • Residential board
• Day care and care
• Health care • Mercantile
• Ambulatory health • Business
care • Industrial
• Detention and • Storage
correctional
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38. Mixed Occupancies
• Buildings may contain more than one
occupancy classification
• Codes require fire-resistive separations
between various occupancies
• Requirements depend on local code
• Reduction in occupancy separation may
be permitted if building is sprinklered
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39. Change of Occupancy
• Frequently occurs
• Can create problems
• May require expensive renovations that
owner not willing to pay
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40. Summary
• Fire behavior in buildings is determined
largely by construction materials and
structural fire resistance.
• Structural fire resistance is determined
most often through laboratory testing.
(Continued)
Building Construction
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41. Summary
• Building codes classify construction into
types based on construction material,
structural fire resistance, and
occupancy.
• Occupancies within individual
occupancy groups present roughly
similar fire risk factors.
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42. Review Questions
1. What is fire resistance?
2. What is the value of standard
fire tests?
3. What is a noncombustible
material?
4. What considerations do
firefighters need to take into account
when they encounter dropped (Continued)
ceilings? Building Construction
2–42

43. Review Questions
5. What are the major occupancy
classifications contained in the
International Building Code® (IBC®)?
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