Fire-Resistive
Construction, Part 2
By Ronald L. Geren, RA, CSI, CCS, CCCA
Editor’s Note: This is the second of a three-part series.
The IBC in addition applies minimum fire-resistance ratings to
building elements that do not depend on construction type. Under
the Uniform Building Code (UBC), fire-resistive construction of
this type may have had specific terms to define the assembly,
while others were loosely defined, such as "__-hour construction"
with no other details. To improve the quality of fire-resistive
construction, the IBC has established 6 basic fire-resistive assemblies.
These include:
Fire Walls ("area separation walls" in the UBC):
These are used to separate a single building into two or more
"buildings." These walls have minimum fire-resistance
ratings of 2 to 4 hours depending on the occupancy group (i.e.
assembly, business, residential, etc.). One thing to keep in mind
about fire walls is that they must be "walls"; they
cannot be used in a horizontal condition.
Fire Barriers: These are used to separate shafts from other
building areas, in exit construction (exits, horizontal exits,
and passageways), in separation of incidental use areas, and in
separation of occupancies ("occupancy separations" in
the UBC). Fire barriers have fire-resistance ratings of 1 to 4
hours depending on the application or occupancy.
Shaft Enclosures: These are additional requirements for
fire barriers used in shaft construction. Shafts are used for
refuse and laundry chutes, elevator and dumbwaiter hoistways,
and mechanical chases. Shafts have a fire-resistance rating of
1 hour where the shaft connects less than 4 stories. However,
if the floors penetrated are rated for 2 hours, then the shaft
is required to be 2-hour rated, as well. Shafts than connect 4
or more stories require a fire-resistance rating
of 2 hours.
Fire Partitions: These are used to separate dwelling units
in the same building, to separate sleeping units (in hotels, care
facilities, etc.), to separate tenant spaces in covered malls,
in corridor walls, and in elevator lobby separation. Fire partitions
have a fire-resistance rating of at least 1 hour.
Smoke Barriers: These are used in various locations as
required to prevent the movement of smoke and have a 1-hour fire-resistance
rating. A similar assembly is the smoke partition, which is not
required to have any fire-resistance rating.
Horizontal Assemblies: These apply to floor and roof construction.
The fire-resistance rating is based on construction type and ranges
from 1 to 2 hours.
In addition to the assemblies described above, building codes
also establish fire-resistance requirements for opening protection
(doors and windows), duct and other through-penetrations, and
joint systems. The protection of these items is only necessary
if the assembly in which they are installed or penetrate have
a fire-resistance rating. The logic behind these additional requirements
goes back to the ASTM test, which requires no passage of flame
or hot gasses. Successful completion of the test would be impossible
if the assembly had an opening, penetration or joint that was
not adequately protected. These items are tested using methods
other than ASTM E 119. For fire-resistant doors and windows, NFPA
80 Fire Doors and Fire Windows is typically used. Fire-resistant
joint systems are tested using either ASTM E 1966 Test Method
for Fire-Resistant Joint Systems or UL 2079 Tests for Fire Resistance
of Building Joints. Through-penetration fire-stop systems are
tested in accordance with either ASTM E 814 Test Method of Fire
Tests of Through-Penetration Firestops or UL 1479 Fire Tests of
Through-Penetration Firestops.
Ronald L. Geren, RA, CSI, CCS, CCCA is the specification writer
and code reviewer for the Phoenix Office of Gould Evans He is
a 1984 graduate of the University of Arizona, and has held various
technical and managerial positions for military, state, and private
agencies. To comment on this article, suggest other topics, or
submit a question regarding codes, contact the author at ron.geren@gouldevans.com |
