2 Layer Sheetrock questions

[Ironbird Studios]

Hello,

I am about to start the sheetrock phase of my basement studio build. I am planning on 2 layers of 5/8" sheetrock with Green Glue.

My first question is how to treat the seams on the first layer. Is tape + spackle necessarry, or just spackle? Or is acoustic caulk best on the 1st layer of seams. (or no treatment at all, since the 2nd layer will cover the first layer with staggered seams.)

I've also read about backer rod + caulk. Is the backer rod necessary? Or is it just meant to save caulk by partially filling up the gap.

The room will be air tight regardless of what application - but I just want to get my facts straight before the sheetrock crews arrive.

Thanks!
gee_lo

[Sebg]

Butt the joints tightly and then just spackle or caulk should be fine to seal the small gap airtight. But don't build it up too much as you don't want to create an airgap to the next layer.

[Rod Gervais]

You would not use backer rod for the seams - the seams should be tight fitting

Backer rod and caulk is for corners - floor to wall - wall to wall - wall to ceiling, and to seal penetrations through the isolating assembly.



Backer rod is NOT a caulk saver - it is a joint saver..... or at least in corners where there is a material behind the drywall.

Caulk fails (longitudinally) when placed into a 3 point connection - it cannot handle that type of movement - thus it develops stress cracks lengthwise.

Backer rod creates a (proper) 2 point connection - which allows the caulk to work the way it is designed to work.

Rod

[jhbrandt]

Originally Posted by Rod Gervais

You would not use backer rod for the seams - the seams should be tight fitting

Backer rod and caulk is for corners - floor to wall - wall to wall - wall to ceiling, and to seal penetrations through the isolating assembly.



Backer rod is NOT a caulk saver - it is a joint saver..... or at least in corners where there is a material behind the drywall.

Caulk fails (longitudinally) when placed into a 3 point connection - it cannot handle that type of movement - thus it develops stress cracks lengthwise.

Backer rod creates a (proper) 2 point connection - which allows the caulk to work the way it is designed to work.

Rod

+1 - I could not have said it better...

Drywall joints on the surfaces must be taped and plastered - so that the gypsum boards become ONE sheet. First layers do not need much 'finishing' - of course. - Let it dry before applying the second layer of drywall. (note: sheetrock = drywall = gypsum board) - it depends on where in the world you live.

Why green glue? What is your STC target?

Cheers,
John