A while back, I answered a question about the required penetration of sheetrock/drywall/GWB into the throat opening of a hollow metal frame. To recap that post, the GWB has to project at least ½ inch into the frame – at least one layer each side. There is more information about that requirement, along with some illustrations, on the previous post addressing this topic.
A question came up recently about what to do when hardware or mortar boxes prevent the ½-inch penetration of the GWB in the location of the hardware. One of the common applications where this occurs is with certain types of electric strikes.
Thanks to Aaron Owens and Gerry Phillips, both of Allegion, I have a definitive answer. Well, I should qualify that – I have an answer from the frame listings for Steelcraft. If your frames are from another manufacturer, you should check their listings to see what is allowed/required. The Steelcraft listings state the following:
Frames that incorporate hardware and mortar boxes may prevent the full ½-inch penetration of the gypsum board into the throat of the frame at the location of the box. If the gypsum board penetration into the throat of the frame is less than 1/16 inch, an application of Classified intumescent caulk must be applied to the gap between the mortar box and the gypsum board. The length of the gap may not exceed 24 inches. Frame may incorporate multiple mortar boxes. Mortar boxes may be installed in all frame components. Mortar boxes shall not interfere with any jamb brackets.