Q: I recently was completing a steel stud and drywall tenant improvement on a single-story business park. The inspector insisted we need draftstopping in the ceiling on a single space. He said it was because it was over 1,000 square feet. I have never had to do that before. Is this new code or was he wrong?

A: The new IBC (International Building Code) and IRC (International Residential Code) have some pretty significant changes and it is easy to get confused. Without reviewing the specifics of the case, I believe he was mistaken. I think the inspector was well intended, but may be referencing the wrong code sections. It is easy to do. He most likely was thinking about a floor/ceiling plenum space and not an area above a suspended acoustical ceiling, as you described. There is a difference. Sprinklers also play a part in the requirement.

Draftstops are defined by the code as a material or device designed to restrict the movement of air within open spaces of concealed areas. Draftstopping materials are defined in section 717.3.1 of the 2003 IBC (International Building Code) as gypsum wallboard not less than 0.5 inch (12.7mm) thick, wood structural panels not less than 0.375 (9.5mm) thick. The panels must be adequately supported and continuity must be maintained.

FLOOR/CEILING

Draftstops are intended to be installed in-line with the wall separating tenants or dwelling units (section 717.3.2). For areas other than residential occupancies, large concealed floor/ceiling areas are not to exceed a horizontal area of 1,000 square feet. An exception permits the elimination of draftstops where automatic fire sprinklers are installed throughout the building.

ATTICS, CONCEALED ROOF SPACES OR ABOVE SUSPENDED CEILINGS

Consistent with the requirements for fireblocking, draftstopping is not typically required for spaces constructed with non-combustible materials (section 717.2). Buildings classified as Groups R-1 and R-2 require draftstops in line with partitions separating dwelling units or between hotel rooms or suites. In nonresidential buildings, draftstops shall be installed such that no horizontal area exceeds 3,000 square feet, unless the building is equipped throughout with automatic fire sprinklers in accordance with section 903.3.1.1.

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