National Gypsum Company, Drywall, Cement Board, Gypsum Board, Finishing Products

National Gypsum Company, Drywall, Cement Board, Gypsum Board, Finishing Products

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.

When constructing a fire-rated gypsum board 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.

How do you achieve a 1- or 2-hour fire-rated ceiling in a duct protection, corridor, or stair soffit 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 Gypsum Board 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 Gypsum Board 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 gypsum board 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.)

My fire-rated design was tested with nails. Can I fasten the gypsum board with screws as an alternate to nails?

National Gypsum Company, Drywall, Cement Board, Gypsum Board, Finishing Products

Yes, screws can be used as an alternate to nails in gypsum board 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.

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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