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Questions about Fire Ratings

Is there a standard for repairing damage to fire rated gypsum board systems?

Our good friends at the Gypsum Association supplied the answer. The Gypsum Association’s publication GA-225-96, Repair of Fire-Rated Gypsum Board Systems, sets out in detail how to make repairs and maintain the fire rating of the damaged system. The method of repair is basically the same for any damage up to 100 square inches in 100 square feet of the system area.

The patching material needs to be Type X gypsum board of the same thickness as the damaged material. The patching material is cut to the same geometric shape as the damaged area, but slightly larger. The damaged area is enlarged to receive the patching material. The patch is then secured by mechanical fasteners; attachment by joint compound only is not acceptable. Use caution when cutting into a gypsum board system because there may be pipes or electrical wires just below the surface.

If the damaged area exceeds the 100 square inches in 100 square feet, the damaged materials must be removed back to the original framing. Inspect the framing to ensure it is not damaged. If it is damaged, replace the framing without increasing the framing spacing. Support ends and edges of boards not backed by framing materials with metal runner track. Mechanically attach replacement material to the framing a maximum of eight inches on centers. Finish the repaired area with tape and joint compound as necessary to produce an acceptable finish.

In multiple-layer systems the joints of the repair material are required to be staggered. Proper repair of multiple-layer systems requires that the face layers of the board be removed beyond the base layer to retain the staggered joint feature.

Apparently there are several manufacturers of clips available to provide mechanical support for patching materials.

What constitutes a smoke barrier, and does it have to be fire rated? The drawings indicated a “smoke barrier” along a corridor in an existing federally owned office building. What raised the question was that the hardware supplier stated that the doors would have to be UL label doors with fire door hardware.

The problem seems to be one of nomenclature. Since the federal government uses the Uniform Building Code, that’s where the search started. Under Chapter 9, Fire-Protection Systems, is the definition for smoke barrier: “Smoke barrier is a continuous membrane, either vertical or horizontal, such as a wall, floor or ceiling assembly that is designed to restrict the movement of smoke.”

Further on, smoke barrier construction is defined: “A smoke barrier may or may not have a fire-resistive rating. Smoke barriers shall be constructed and sealed to limit leakage areas exclusive of protected openings.” The paragraph continues to define calculation of leakage.

The code defines opening protection and states that openings in smoke barriers shall be protected by self-closing devices or automatic-closing devices … .” Here is where the hardware requirement comes in.

In the situation in question, the corridor is an egress corridor and would have rated walls. Since rated walls extend from floor to ceiling, they also act as smoke barriers. In this case, the nomenclature should have indicated that the wall in question was a rated assembly. Or in other words, while the wall serves as a smoke barrier, the more restrictive use of the wall is a fire separation and should have clearly stated that.

About the Author

Donald E. Smith, CCS, is AWCI’s director of technical services. Send your technical questions to him at [email protected], or fax them to (703) 534–8307.

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