Interpretation #7356

The typical gap at the top and bottom of steel studs or the small holes punched to allow electrical or other systems to be run through the wall does not create a "communicating cavity". However, the local authority needs to look at the wall while at least one side is open to make certain these gaps and holes are typical and not excessive. Manufacturer's installation instructions typically specify a specific sized gap at the top of the stud in fire rated partitions. (e.g. 22mm) Presumably this is to allow expansion when attacked by fire. However, these materials are subject to cutting in the field and should be inspected to verify compliance with the manufacturer's instructions While the ICC interpretation specifically states the gaps and openings do not constitute communicating cavities, it is telling that neither the UL code change proposal nor the UL engineers mention such gaps and openings. Further information: Manufacturer's Installations may specify a deflection gap at the top of the stud. Information such as this appears on a detail from the USG Steel Stud Installation Details: Top Gaps 10 mm standard 15 mm fire rated to 3.6m 22 mm fire rated 3.61-5.4 mm