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Callers to our 1-800-NATIONAL® Technical Assistance Hotline frequently ask the following
questions about gypsum board systems: |
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What does it mean to say that a particular wall or ceiling system
has achieved a 1-hour fire rating?
The term "1 hour fire-rated system" is generally used to refer to a system that
has been shown, in a carefully controlled laboratory setting, or by rigorous technical
analysis, to be capable of limiting the transmission of high temperatures to a specified
maximum, and to meet other requirements, for at least 60 minutes. The wall systems
used in such tests are typically constructed with extreme precision. The carefully
controlled test procedure is intended to evaluate fire resistance under specific
laboratory conditions for comparison purposes, and does not guarantee that a similar
system installed in a building that is exposed to actual fire conditions will perform
in the same manner as the laboratory test.
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When constructing a fire-rated wallboard partition, must the exact
stud size specified in the tested design be utilized?
No. Specified wood or steel stud sizes are minimum unless otherwise stated in the
design. Wood stud walls may contain fire retardant treated studs as well as untreated
wood studs. The hourly ratings for steel stud partitions are maintained when the
steel studs are of a heavier gauge and/or larger dimensions than specified in a
design.
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How do you achieve a 1- or 2-hour fire-rated ceiling in a duct protection,
corridor, or stair suffit without incorporating a floor/ceiling design?
I-Stud Cavity Shaft Wall Systems can be erected horizontally and used as economical
fire resistive assemblies for corridor ceilings, stair soffits and protection for
mechanical ducts. Depending on the span of your ceiling, I-Stud and J-Track depth
and gauge required will vary.
The I-Stud Cavity Shaft Wall Systems for Horizontal Duct Protection consist of I-Studs
24" o.c. with 1" Fire-Shield Shaftliner panels inserted in the steel tabs, and three
layers of 1/2" Fire-Shield C wallboard attached to the stud flanges opposite the
Shaft liner panels. This system provides fire protection for mechanical ducts and
has been tested from both sides. (Refer to WHI-694-0300.1.)
Single layer 5/8" Fire-Shield or Fire-Shield C wallboard attached to the stud flanges
opposite the 1" Shaft liner panels provide one-hour fire protection when used as
a corridor ceiling or stair suffix. Two layers of 1/2" Fire-Shield C wallboard attached
to the stud flanges opposite the 1" Shaft liner provide two-hour fire protection
when used as a corridor ceiling or stair suffix. (See ICBO Evaluation Report #3579
for allowable value and/or conditions of use concerning material presented in this
document. It's subject to re-examinations, revisions, and possible cancellations.)
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My fire-rated design was tested with nails. Can I fasten the wallboard
with screws as an alternate to nails?
Yes, screws can be used as an alternate to nails in wallboard designs.
Diameter of screw head, length of the screw and shank must be the same size or larger
than nail size specified in the design.
Note: Spacing of screws must be the same as the spacing of the nails specified in
the fire rated design.
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Can I add glass fiber insulation to a fire rated partition design
when it is not specified as a component?
Yes, glass fiber insulation of a thickness not exceeding the depth of the stud is
OK to add to the stud cavity.
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Do all interior non-load bearing steel studs have to be fastened
to the floor and ceiling tracks?
No, secure studs located adjacent to door and window frames, partition intersections
and corners with 3/8" pan head through both flanges of studs and tracks or by using
a stud clincher. (Reference ASTM C754.)
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