Double layer of gypsum

I know this is around here somewhere, but after an hour of searching I haven't found it. When doing a double lair of gypsum board, the first goes on with screws, then the gaps are acoustically sealed, then the second lair staggers the seams. How do you attach the second lair? I'm assuming screws would transfer sound right? Am i supposed to glue it? If so, with what? Thanks

How do you attach the second lair? I'm assuming screws would transfer sound right? Am i supposed to glue it?

First one is straightforward, longer screws. The goal is to try and create a single mass with the two layers. Steve will correct this if I am wrong, but as I understand it the jury is out on whether to glue or not to glue. The more common belief is not to glue. The USG Gypsum Wall Manual is full of this sort of information, including screw types, screwing schedules (spacing) and much other useful data, tips and tricks. There is a link to it at the top of the forum. I strongly recommend you d/l it and study it. Good Luck!

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=598 The 2nd post in that thread is by E.F. Knightfly, and he says ... lair - The den or dwelling or hideaway of a wild animal :) layer - A single thickness of a material covering a surface or forming an overlying part or segment: a layer of dust on the windowsill; a cake with four layers. I know sometimes I hide in my basement den. :) Grrrrr :)

Bob, I hope that was all meant in fun - without at least a "smiley", sometimes people take things like that more as mocking - Still, if yer gonna put words in me mouth, I prefer chocolate or pizza 8) Ptown, the answer to your question depends partially on the framing you will use - if using a single frame with no resilient mounts, then screws through both layers on each side of the wall WILL cause noticeable isolation loss. If either side of a single frame has resilient mounts, the damage from screw flanking is almost totally negated by insulation fill within the wall. If doing staggered studs on common plates, you'll get maybe a dB or two less isolation using screws for both layers, that's just a gut feel though - With full double frames, no problem whatever. Use half as many screws for all but the final layer on each side of the wall, then full schedule (check the USG manual as Andre mentioned) for the top layer. The possibility of glue softening the wallboard and causing Laminating screws to pull through caused Rod and me to decide that wasn't a good way to go - timing is too critical on how long you let the glue set before laminating, plus it's not clear just how strong the shear is with the stripe glue/laminating screw methods of attachment. Not worth the risk in our opinion... Steve

Yeah, yeah, layer, I know. When I typed this I had just finished working my ass off for 12 hours straight and several barley sandwiches.... So I'm going to go with the screws, it's a two wall construction, double LAYER of gypsum on the exposed sides. Thanks

OK, ya got LAYER right, now let's spel SKRUZ curreckley... :wink: Know whacha mean about 12's, I work 2 12 hour daze then 2 12 hour nites then (if I'm lucky) 3-1/2 days off, then do it again... Steve

Gluing doesn't work. It's a nice concept but it'll only take 30 mins of fooling with that to discover that it's an impossible dream. As mentioned just use screws for both layers.