acoustic caulk vs 100% silicone

Just curious as to what's best to use where. I've been using 100% silicone to seal up cracks in the wood behind my beef (3x drywall) but am curious what to use for the cracks between the cleats and the drywall. (I'm doing the Sharward method of beef) I noticed that he used the acoustic caulk for the cleats/drywall....but what is the benefit of using it? Is it more dense than 100% silicone (because that seems pretty friggin dense to me)? Is it cost? Thanks for any input! -Aaron

Aaron, this has nothing to do with density - and everything to do with keeping the joints airtight....... acoustic caulks are some of the messiest caulks to work with - they stick to everything and are really much more liquid that the silicone caulks - in fact the are often referred to as floppy caulks - because they are just that. I often recommend that people turn to butyl caulks when they can't swing acoustic caulks. Don't get me wrong - silicone caulks will work fine except that I do not believe that will adhere well to the raw edge of a piece of cut drywall - and both of the other caulks will. Please remember to use backer rod before you caulk - otherwise not matter what you use - you will have caulk failures....... Rod

Rod, is there any substitute for backer rod? I've looked all over for it in Chile and I can't find it. What might I be able to use instead? - Stuart -

Thanks for the reply, Rod. Though to be honest, I have yet to see anything that 100% silicone will not adhere to.....rough edge of drywall included. So, is the caulk (be it 'acoustic' and/or 'silicone') just for the sake of airtight-ness then?

Pure L wrote:

Thanks for the reply, Rod. Though to be honest, I have yet to see anything that 100% silicone will not adhere to.....rough edge of drywall included. So, is the caulk (be it 'acoustic' and/or 'silicone') just for the sake of airtight-ness then?

Correct Rod