Foaming or non-foaming caulk?

Posted: Tue Aug 05, 2008 3:35 am

I've been researching caulk here in China, and it seems most are the foaming type like these:
http://b2b.hc360.com/supplyself/38084849.html
http://b2b.hc360.com/supplyself/40981714.html
http://b2b.hc360.com/supplyself/2385645.html

I was told they expand to something like 50 times its original volume, and then you cut off the excess once it's done expanding.

So are these foaming caulks ok? (In their description they say these products are great for sound isolation.) Should the caulks be non-foaming?

Posted: Tue Aug 05, 2008 8:49 am

From what I've seen here in the states, the expanding foams are more of a general insulation than a real caulk.

In terms of general construction, the expanding foams are quite useful. However, about the only places I found a use for it would have been around window and door frames... but since I had enough regular fiberglass, it made more sense to use a bit of the scraps to fill in those gaps, and then caulk with OSI's SC-170, acoustical sealant.

For caulking gaps and seams, it's pretty much accepted that OSI's Acoustic Sealants are the real deal...
SC-170 and SC-175

I'd download the data sheets and try to locate something similar.

The real problem I see with the expanding foams is that they don't really hold up to exterior weather conditions too long before they will become brittle and begin to break down... that and the ones that really expand... like the 50x stuff, can actually explode apart the assembly if it doesn't have enough free space in which to expand.

There are some low volume (3x and 4x) expanding insulating foams that are gaining popularity in wall insulation applications. Especially as a renovation for wood structures. But even then, standard caulkings are used for sealing joints and edges of assemblies.

HTH

Posted: Wed Aug 06, 2008 3:44 am

The problem right now is, I cannot seem to find any acoustical sound sealant/caulk/kit in China. They only have the foam type as far as I can tell, or just normal kit not specified for acoustic purposes.

So if I had to pick between a foaming caulk that sayd it can do sound isolation, and a regular kit (not specified for acoustic purpose), which should I pick? Of course, I can try to order the real deal outside of China, but it's going to be complicated I think with China's customs.

Posted: Wed Aug 06, 2008 4:13 am

Hmmmm...

If I'm wrong, I hope Rod or Andre' will jump in with correct info.

For seams and cracks, I would still look for long-life butyl rubber sealant caulks.

If those aren't available, I would maybe look for any type of rubber based tub and tile caulk.

Lastly, I'd look at silicone... exterior grade.

The property you are looking for in your seam caulk, is flexibility. The last thing you need is the caulk to shrink and open gaps. It needs to stay soft and have a good moisture resistance.

Given the standard construction methods I'm familiar with, I just don't see the expanding foams being any better at sealing a crack than a controllable caulk.

Think about it this way.... if something expands, even by as little as 3x, how do you control its application with any degree of accuracy? Especially in a corner.

Posted: Wed Aug 06, 2008 7:29 am

Expanding foams will not only NOT get the job done - but they can act as a bridge between 2 surfaces - and do not have enough mass to do anthing on value for isolation.

I wuoldn't even use them for doors or windows inside the building - you are much better off with fiberglass or rockwool insulation (do not pack tightly) and then caulked edges.

The directions Max has given you are good ones.

Rod

Posted: Thu Aug 07, 2008 8:56 am

Thanks for the help! If I can't find the acoustical sound sealants here, I'll get the stuff you guys recommended as alternative.

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