See attached. How does the high lighted area relate to the blue underlined sentence. It appears to state a minimum of 1-1/4" depth needed of firestop material and then the note mentions a min 1/4" depth and max 1". What is the minimum for a two hour assembly? The issue in the field is the contractor has installed the drywall up next to the duct insulation and some are saying the drywall should be cut back at least 1-1/4" to allow for 1-1/4" of firestop material. What is the proper way to seal this application? Thanks for your help.
Good morning,
The 1-1/4” depth of sealant described in item #5B refers to the depth of sealant through the gypsum boards. In this case the two 5/8” sheets of gypsum equal 1-1/4” so the sealant needs to fill this entire area to the inner surface of the gypsum boards.
The minimum ¼” and maximum 1” described in Note #2 refers to the annular space between the compressed insulation surface and the edge of the gypsum opening.
The gypsum should be cut back a minimum of ¼” to a maximum of 1” from the compressed insulation surface and then the sealant should be installed 1-1/4” into the space to fill the thickness of the two layers of gypsum.
If you have any questions, please reach out to our customer service team at 1-800-879-8000 (US) or 1-800-363-4458 (Canada) for assistance.
Thank you,
Rudy Jarvis
Fire Protection Engineer