Acoustic sealant versus latex caulk

motmclergy · Post by **motmclergy** » Thu Sep 02, 2004 5:02 am

Hi there,

I've read everything I can find here on this, including the reference thread about caulk and insulation, and this question is not addressed. Forgive me if this is rehashing something that's been covered before.

I've seen many references to the necessity of lots of caulk when building "soundproof" walls, and they usually specify acoustic sealant. From reading here, I discovered that "acoustic sealant" is different than latex or silicone caulk. I assume acoustic sealant seals out sound better than latex caulk; but how much better? I.e., how necessary is it, and how much transmission loss/STC do you lose by caulking with latex? What about two beads of latex versus one bead of acoustic sealant? I can buy latex caulk easily and cheaply; I'd have to find a source for acoustic sealant and perhaps find someone with a tax id (contractor's license) to buy the sealant for me (from a wholesaler/contractor supply house). If the sealant is really worth it, anybody know where a guy off the street can walk in and buy some in the Detroit area?

Thanks,
Larry

blakemcginnis · Post by **blakemcginnis** » Thu Sep 02, 2004 5:28 am

I was having trouble finding acoustical caulk also and I found a dealer online, White Cap, that sells 29oz USG Acoustical sealant for $4.44 a piece. I ordered 12 for around $47.00 before shipping (shipping was approx. $16.00). Here is the URL:

long link

This only took 3-4 days to arrive and was actually cheaper than the decent caulk I could get down at Home depot or Wal-Mart.

motmclergy · Post by **motmclergy** » Thu Sep 02, 2004 5:44 am

thanks for the link. anybody have any hard data on latex vs "acoustic" caulk - price/performance ratios, etc. If i can use twice as much latex and get the same performance as acoustic, at the same or lower cost, with much less hassle in buying it... you see what i'm sayin'.

ld

Post by **Aaronw** » Thu Sep 02, 2004 6:08 am

Giles is in the Detroit area. He may know where to pick it up locally...

knightfly · Post by **knightfly** » Thu Sep 02, 2004 6:51 am

Larry, welcome to the board -
There are several reasons for using the acoustic rated stuff -

1 - With the possible exception of GE's Silicone II, none of the so-called "homeowner" caulks will flex enough to guarantee an airtight seal in your construction after settling, shifting, and all the other things construction tends to do when we least want it to -

2 - These tubes we talk about are 29 0z each, some are even 32 oz - it takes THREE of the standard 10 oz tubes to equal one of the big ones.

3 - The GE stuff costs as much for a 10 oz tube as the REAL stuff costs for 3 TIMES as much - the gun for the big tubes runs around $15, so it doesn't take many tubes in a job before the gun is paid for.

4 - If sound proofing is NOT important to you, skip ALL this and just build normally

5 - If, however, you plan to use your studio for more than a couple of years, and you do NOT like the idea of ripping things out so you can get to joints that USED to be soundproof, it's worth the slight hassle of finding the right stuff.

6 - Did I mention that the acoustic stuff, even when buying it online, is actually CHEAPER?

I hope this puts things more in perspective for you... Steve

motmclergy · Post by **motmclergy** » Thu Sep 02, 2004 1:12 pm

Thanks for the welcome Steve, and the helpful info. i should have payed attention to the size of the tubes - i just assumed that 29 ounces was the "regular" sized tubes, not the big ones. since the acoustic stuff is cheaper and better, that settles it definitively for me - even if i have to order it online.

hey Giles, do you know where to get acoustical caulk in D-town?

ld

4midori · Post by **4midori** » Wed Dec 08, 2004 8:05 am

Hi,

I tried the SC-175 stuff from OSI.
http://www.osiproseries.com/adhesives/p ... d-sealant/

I returned it to the store because it dried somewhat brittle, not flexible. I switched to silicone caulk instead. From your post above it sounds like this is a big mistake.

Other ideas? Is there another brand I can try? Where I have caulked behind my walls, I cannot get at them, they are bolted down. But I can get at the front side, since I mounted the drywall on the opposite side of the wall as usual (stud cavities exposed).

Thanks,

ben

z60611 · Post by **z60611** » Wed Dec 08, 2004 10:25 am

4midori

Is there another brand I can try?

http://www.johnlsayers.com/phpBB2/viewt ... sc&start=2

4midori · Post by **4midori** » Wed Dec 08, 2004 1:31 pm

Thanks for the link.

Should I be worried that I used DAP silicone caulk on the back sides of the walls where drywall joins? They are bolted down and I can't get at them!

-Ben

Sen · Post by **Sen** » Wed Dec 08, 2004 9:58 pm

Hey guys,who ever has used the acoustical sealant b4...How easy/hard is it to sand this material?? Steve pointed out that it flexes more than your ordinary sealant, which I would imagine would be very hard to sand due to its elasticity...

So how hard is it to sand down, or do you just apply it very carefully so it's flush and smooth with the surfaces being caulked , so you don't have to sand it down.Sorry for dumb question, but I'd just like to know how it works

thanks

motown59 · Post by **motown59** » Thu Dec 09, 2004 2:45 am

The caulk shouldnt be used where you would use joint compound only at edges of panels and inside walls around electrical boxes. Depending on how good your technique is around the edges determines if you have a high spot to squish down.
The GE silicone II Door & Window is pretty good stuff for the home center selection. I've used it on residential windows and they're still soft and wet looking months after..but it is $3 something for the small tube. DAP Alex Plus I've used in the kitchen for cabinet mounting...it kind of gets hard but hasn't shrunk..much(!) after 5 years..but around a door/ window, especially one where it meets the outside, or inside a wall I wouldn't use it. But I wouldnt worry about it if you've used it already inside somewhere...there too much to worry about if you own a recording studio anyways!

Sen · Post by **Sen** » Fri Dec 10, 2004 4:30 pm

thanks motown,
it's just that i've read so many times how you need to "caulk and sand well" and I was wandering how "sandable"

it is...
cheers

knightfly · Post by **knightfly** » Sat Dec 11, 2004 12:51 am

Sen, you've not heard "caulk and sand well" from me; any caulk worth using in your studio would just ball up and clog sand paper. In order for a material to sand well, it needs to be hard and dry. Good acoustic caulk will do neither - basically, you were right; you just need to be careful on application, and wipe excess with recommended solvent for the caulk you have; once done, you don't disturb it til it has had the prescribed cure time.

For areas you want to sand, unless they MUST be caulked, it's better to use drywall "mud", or joint compound (not many containers are labeled "mud", it's just easier and quicker to say)

Hope that helps... Steve

Sen · Post by **Sen** » Sun Dec 12, 2004 1:32 am

Sen, you've not heard "caulk and sand well" from me

well the idea its self sounds very stupid, so I would never have thought it would come from someone like you, Steve

, but I can tell you I've read this a few times on message boards (I actually tried searching HR where I've seen it mentioned the most to no success) and always wandered WTH

How do you actually sand the thing if it's supposed to flex that much? It might have been that ppl were saying "caulking" instead of "mudding" who knows.....I guess I was just ignorant enough to even have doubts that it could(not) be done

z60611 · Post by **z60611** » Sun Dec 12, 2004 4:25 pm

sand caulk?

I've always assumed that if you're covering the caulk with trim you leave it bumpy and ugly, and otherwise you smooth it with a putty knife the same way one does with silicone caulk when putting glass walls in a shower stall.