Question:  I am working on a single floor retail building with storage in the basement, which has a sprinkler system. We have specified 3/4-inch Sturd-I-Floor tongue-and-groove (T&G) plywood as floor sheathing. The building official/fire marshal has commented that no evidence has been presented on smoke passage through the T&G joints. Is there some sort of documentation that discusses this?

Answer:  IBC Section 702.1 provides the following: "SMOKE BARRIER. A continuous membrane, either vertical or horizontal, such as a wall or floor or ceiling assembly, that is designed and constructed to restrict the movement of smoke." Section 709.2 says that smoke barriers shall be of materials permitted by the building type of construction. These code provisions appear in the IBC 2000, 2003 and 2006.

We do not have or know of any data related to materials already recognized as smoke barriers, nor do we know of any established smoke barrier performance criteria or established test methods (ASTM, ANSI, ICC-AC, etc.) for evaluating smoke barriers. To the best of our knowledge no such criteria or test methods exist.

Your inquiry is the first we've had regarding the efficacy of wood structural panels as smoke barriers. Note that the IBC says, "restrict the movement of smoke." The code does not mandate elimination of smoke movement. In our opinion, merely constructing the floor deck of a single layer of wood structural panel floor sheathing with T&G edges, or blocking meets the intent of the code because the deck is continuous and the movement of smoke is restricted. Two-layer floor construction with joints staggered is another option.

It is our opinion that the code official's concerns, while undoubtedly well intentioned, are not supportable by any code reference or test method.