Caulking The Boards

Hi we are finally about to put up our walls - 2 x 15mm gypsum soundbloc boards - as a staggered Green Glue sandwich onto a wooden stud framework . I am considering putting a thin bead of caulking silicon onto the wooden stud-work immediately prior to fitting the first board with the reasoning that it would provide dampening, form a stronger bond and require less drywall screws to hold it up - anyone had a good experience with this? Also once the first skin goes up should we caulk all the gaps between boards or would a jointing skim plaster be better? Thanks for sharing!

I am considering putting a thin bead of caulking silicon onto the wooden stud-work immediately prior to fitting the first board with the reasoning that it would provide dampening, form a stronger bond and require less drywall screws to hold it up

Unfortunately, that won't accomplish what you are hoping. You still need to use the full nailing schedule (you can't substitute any type of "glue" for nails with drywall, and in any even the nails "short-circuit" the caulk, so the effect would be negligible. The only possible advantage would be a better seal around the nail holes, but that's not really an issue in any case. Finally, since you are going to do GG between the drywall layers, there's your damping! That's exactly what GG does: constrained layer damping. - Stuart -

Hi Stuart thanks for your opinion on fixing boards to studs Any thoughts on whether its worth the effort to caulk the gaps along the sides of each board on the first skin (we will of course caulk the gap at top and bottom of each board) Thanks!

Stuart...can u explain 'shorting the caulk'

Stuart...can u explain 'shorting the caulk'

The caulk would provide some degree of decoupling and therefore improve isolation to a certain extent, and it would also provide damping, ... if it was just allowed to sit there in between the two layers. It would do that because it is somewhat resilient ("springy"). But as soon as you drive a nail or screw through it, to hold the drywall in place, you "short circuit" that resilience ("springiness"), since the nail bypasses the caulk, and directly connects the drywall to the stud: it creates a hard mechanical connection that sound can travel down, regardless of what the caulk does. It just totally bypasses the caulk. This is also called a "flanking path", since it provides a route for sound to "get around" the isolation. So the caulk becomes irrelevant. As soon as you put one single nail in, the caulk is no longer having any useful effect. Preventing such flanking paths is very important, if you want good isolation ("soundproofing") for your studio. - Stuart -

Soundman2020 wrote:

Stuart...can u explain 'shorting the caulk'

The caulk would provide some degree of decoupling and therefore improve isolation to a certain extent, and it would also provide damping, ... if it was just allowed to sit there in between the two layers. It would do that because it is somewhat resilient ("springy"). But as soon as you drive a nail or screw through it, to hold the drywall in place, you "short circuit" that resilience ("springiness"), since the nail bypasses the caulk, and directly connects the drywall to the stud: it creates a hard mechanical connection that sound can travel down, regardless of what the caulk does. It just totally bypasses the caulk. This is also called a "flanking path", since it provides a route for sound to "get around" the isolation. So the caulk becomes irrelevant. As soon as you put one single nail in, the caulk is no longer having any useful effect. Preventing such flanking paths is very important, if you want good isolation ("soundproofing") for your studio. - Stuart -

So how does one resolve this?

That depends on your isolation design. If you have fully decoupled 2-leaf walls, where the inner-leaf is on a separate stud frame that does not touch the outer leaf, then you don't need to do anything: just put up the drywall as you normally would. The same applies if you are using staggered-stud design. But if you are using a single-stud design, then use either resilient channel, or use isolation clips plus hat channel. If you could post more information about your design, then I can be more specific on how you should go about building it. - Stuart -