AVS Forum Special Member
Join Date: Aug 2001
Location: Lynnwood, WA USA
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It is well worth putting drywall in the joist cavities. The drywall itself is pretty inexpensive and it is relatively easy to do. The cost of the Green Glue adds up, but it is well worth it. It is much better to apply mass to the bottom of the floor above to minimize footfall noises that to try to block it out once the vibration gets in the the structure.
The measurements don't need to be exact. Measure each cavity as you go along and cut the drywall around 1/4" less, giving you 1/8" or so on either side. I found that it was easiest to use 4' long sections of drywall, cutting "strips" out of the 4x8 sheets of drywall. Small gaps on the sides won't matter, the goal is mass. The most difficult parts are cutting off any screws or nails that are hanging down from above, and working around ductwork. Neither is really "difficult", "time consuming" would be a more accurate description.
Last edited by DaveClement; 09-10-2018 at 06:18 AM.