Soundman2020 - Studio Design Forum

Hello! I'm doing research all over the place to get ready for my build. I came across this: https://www.soundproofingcompany.com/so ... tersection

Is specifically says:
"Don’t try and leave a gap. The illustration shows a gap that is 1/32 of an inch. Most drywall installers do not hang drywall to this tolerance, but the point is you are not trying to leave a gap on purpose. After drywall is hung, seal the seam tight with acoustical sealant."

Which is contrary to the info I see on this site (and elsewhere) that says to leave a 3/8" gap and stuff it with cord and caulk. an someone clarify?

Hi ScotcH,

The goal is to make sure you get a good seal with the caulk. By leaving an intentional gap (which can be even smaller, like 1/4"), and then stuffing it with backer rod, you are giving the caulk to touch 3 sides (drywall, floor, and backer rod). Without the backer rod, the caulk has nothing to touch, and can shrink, crack, or just get pushed back further into the the gap (whether left intentional or not), which will cause the caulked joint to fail, and you lose your seal. Leaving a gap and using backer rod just allows you to get a solid seal that will last. Plus is saves caulk so you don't have to pump entire tubes of it into the gaps to create that seal.

If you don't have it already, get "Home Recording Studio - Build It Like The Pro's" by Rod Gervais. He goes WAY more into detail about it. This book is the bible when it comes to studio builds, large and small. He uses the gap + backer rod approach in all of his builds, and he's one of the leading studio builders in the world. If it's good enough for him, it's good enough for me.

Jag94 is absolutely correct. Once you've used the backer rod & caulk approach it makes complete sense, I promise!

Cheers,
Jennifer

Yes, the backer rod makes perfect sense, I understand that ... I just found it odd that the link specifically says "do not leave a gap" when I was under the impression that you WANT a gap so the walls and ceiling drywall is completely decoupled (and then the air space filled with backer and caulk). To me it reads like the walls and ceiling can be connected without any impact on sound isolation ... which I thought was incorrect

ScotcH wrote:Source of the post Yes, the backer rod makes perfect sense, I understand that ... I just found it odd that the link specifically says "do not leave a gap" when I was under the impression that you WANT a gap so the walls and ceiling drywall is completely decoupled (and then the air space filled with backer and caulk). To me it reads like the walls and ceiling can be connected without any impact on sound isolation ... which I thought was incorrect

It is definitely contrary to all of the recourses I've read about sound isolation in walls. But the gap is not for decoupling. It's to make sure you're getting a proper seal at the edges of the drywall. Caulking can be bad right out of the tube, it can go bad, it can shrink, crack, or simply not fill the gap properly, no matter how small the gap is. So backer rod gives us an edge to make sure the caulking has something to touch. At the end of the day, do what fits your budget and what you're comfortable with. But if you're looking for maximum isolation, I'd stick with methods used by the professionals.