re post #151
Think about what is required to get acoustical sealant into the vertical gap in:
If it's a big ceiling you might get away with coating one or two edges of the drywall with acoustical sealant, but odds are you'll have gaps that it gets scraped off for one reason or another, and once its up there's nothing you can do about it. But the problem isn't with the first piece where you have oodles of room -- its the last piece of ceiling drywall where your tolerance is so small you're guaranteed to scrape off the goop (acoustical sealant) as you put it in place.
In a closet or narrow up/down soffit spot such as near an overhead pipe/duct or I-beam/joist, you might have to coat three edges or even four. There's no way to lift drywall with four edges covered in goop without scraping it off on the walls on the way up.
Similarly, you might be able to do the ceiling, but you can't also do the floor -- one side or the other, you'll be scraping the goop off by putting the close fit drywall in place.
That said, sealant is kind of sticky, and you might get away with running the goop in the corner before putting the drywall into it, and hoping it'll squeeze into the gap rather than uselessly as most of it ends up behind the large flat side of the drywall sheet -- not remotely optimal, but better than having it scrape off on the walls.
There's also some drying possible with acoustical sealant -- but if you have lots of it, it will stretch nicely. A quarter inch, is about optimal.
Note that too much gap doesn't work at all, within a few months the sealant will fall off one edge or another -- that's why the backer rod has to be in there so the sealant is 1/4" deep as well as tall -- acoustical sealant lasts really well in 1/4 inch gaps. (the backer rod provides no soundproofing of itself, its just there to keep the acoustical sealant optimal)
The acoustical sealant is for where cracks in mud/tape tend to appear -- look at your own house, I'll bet you'll see more cracks in corners than on long walls. There's more movement in corners than in long walls.
So my (Rod's) drawings are acoustically and 'structurally' sound -- 'structurally' used here to mean it'll last.
They're also much easier for tired stupid helpers to put up without creating failure.
FYI, my two drawings were based on some writings of Rod Gervais, and were subsequently modified a few times until Rod Gervais approved them. The second one for example is named 'zigzag4.gif'. That's because he rejected 'ziggaz1.gif', 'ziggaz2.gif', 'ziggaz3.gif' which matched his post, but not what he understood.
If someone can get Brian to look at this and say Rod is wrong, I'll accept it. But no one else from the soundproofing company trumps Rod in my opinion.Edited by BasementBob - 2/22/14 at 10:16am