# Green glue



## chaosnetwork4 (Mar 20, 2009)

I have a stupid question: If you use green glue on a ceiling between two sheets of 5/8" drywall do you screw the second layer as well as the first? Seems like you have too, but then how does the green glue work so well? Also, won't cutting holes in the ceiling for light fixtures defeat the purpose of using green glue for sound isolation to the above floor?


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## bpape (Sep 14, 2006)

Yes. You do have to screw both of them. Even with the screws, 99% of the drywall surface is separated and flexible which adds additional extension to the extra mass.

Yes. Cutting holes does defeat the purpose. If you must do can lights in the field, they need to be enclosed in 3/4" MDF boxes and only 1 small hole for the Romex to enter and that caulked tightly.

Bryan


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## Ted White (May 4, 2009)

Alternately you can build a box from OSB and laminate cement board to the inside. Avoid even fire-rated drywall, as the paper can delaminate and isn't fireproof.


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