Originally Posted by Timmeh!
The MDF is not up yet, just curious about the process of attaching the drywall to it.
Thanks for your suggestion - I'll definitely look into the green glue.
Ahhh... that's what I get for working all day on two hours of sleep and then trying to comprehend... (Hell, comprehension after 8 hours of sleep is bad enough)
I had originally wanted to use MDF, but the cost was almost double that of the OSB I ended up using. So, thankfully, cost factors drove me to a better product.
I used 2" drywall screws to attach the OSB to the studs. Then 1-1/2" drywall screws to attach the 1st layer of gypsum to the OSB, and 3" decking screws to attach the 2nd layer of gypsum.
As far as glues and adhesives...
I used PL400 on all the ceiling joists when I put the OSB up... and PL400 when I put the OSB up on the walls of the tracking room. A single wide bead along the joist/stud.
After attaching the OSB, in a horizontal orientation, I stuffed backer rod around the perimeter of the OSB at the ceiling, vert wall corners and floor. Then I sealed all the joints with OSI's SC-175 acoustical caulk.
For the first layer of gypsum, I attached this layer in a vertical orientation. I used OSI's drywall adhesive in a random pattern and 1:1 - tube to gypsum ratio. Again, I caulked the corners and used backer rod to stuff the corners, and sealed them with OSI SC-175 and in the Control Room, I switched over to Green Glue Corp's, SilenSeal.
I wanna mention the SilenSeal product... It may be a pseudo "better" product than the OSI on paper, but I have some real issues with this stuff... It's a MAJOR PITA to work. It sucks as far as handling. The 7 cases of tubes I purchased had major issues, in that there was a massive air bubble in over 3/4 of the tubes. It causes the caulk to continue flowing after you take pressure off the gun... and the shit came exploding out of the tube when I got down to that bubble. On more than one occasion, the blast blew the caulk out of the joint and it created one hell of an aggravating mess.
Another thing I discovered is that it has one hell of a shrinkage problem... The stuff exhibits about a 50% shrinkage. So, you end up using twice as much caulk as you do with the SC-175. But since the SilenSeal is about as thick as baby shit, you can definitely fill whatever gap you're filling. And it does fill the gap better than the OSI since it is such a thin viscosity compared to the OSI... but if I had it to do over... I'd use the Silenseal on the OSB and the OSI on everything else.
I used Green Glue for the Iso Booth and Tracking rooms in a 2:1 - Green Glue to Gypsum ratio. When putting the Green Glue down, you want to put down pretty wide beads... not thin beads. The recommendation I got was to make the beads at least 1/4" wide or wider. Oh... and this stuff is sticky... not just a little... but SERIOUSLY sticky. Don't let the stuff get on anything you don't want it to stick to, or stick to it... EVER. I accidentally got some on the floor and on a couple of pieces of scrap OSB. almost a year later, the scrap OSB is STILL sticky as hell and anything that touches it... oof. You'll play hell getting it un-stuck. (yeah, I hung on to it just to see how it acts.)
The thing that I think actually helped get the STC up as high as it is, was the screw patterns (and the 24" OC stud spacing) used to attach the OSB and gypsum. I used the info Rod supplied in this sticky
at RO. (Click on the Gypsum Construction Handbook at the USG site.)
The key is to get a good consistent screw spacing. I worked as hard as I could to keep a 16" spacing on the screws for each layer. I had quite a few folks tell me I was insane using that many screws on each board. Then too, the proof is in the pudding, as they say... but the goal you are trying to achieve is not just to get the shit on the walls. The goal is to try to make your walls (and ceilings) one homogeneous mass. Unless you use enough fasteners, you'll not quite achieve that goal.