This is related to this question: How can I attach drywall directly to cinder blocks without using furring strips?

I am replacing an older strip of drywall that is at the bottom of the wall The upper side of the wall is older drywall which seems to be like 1-2/16" thicker than the new drywall In an attempt to install my new drywall flush with the old one I have used some pink sill gasket foam enter image description here

I will install this between cinder blocks and the new drywall. I will use tapcon screws to secure the drywall on the cinder blocks (long discussion about why in the above mentioned thread)

Does this sill gasket foam compress in time? Do I risk to see cracks later when the material settles and gives up under the pressure of the on top drywall secured with tapcon screws ?

  • 1
    It will compress just by you holding it in your fingers. It is just foam. You need something solid(wood) for non compression. The foam is just to prevent air leaks between two solids, wood/cement.
    – crip659
    Commented Oct 9, 2021 at 22:09
  • consider the compressing after it was compressed by tightening the screws
    – MiniMe
    Commented Oct 9, 2021 at 22:25
  • Why are you over thinking this? You can easily tape and mud 1/16" or 1/8" and not tell there was a difference in thickness.
    – Gunner
    Commented Oct 11, 2021 at 20:32

1 Answer 1


That foam will absolutely compresses. Your question said 'over time'. No, it does not compress over time. But, you do not need 'over time' for it to be a problem.

This is what will happen:

  • You will install the foam in the block using some clever method of keeping the foam in place until the drywall is hung.
  • You will blue bolt the drywall to the block with the foam between.
  • You will coat the bolt with mud, finish, and paint.
  • You will lean on the wall which will compress the foam and pop the mud.

So don't do it!

Also... The block will sweat. The foam will keep the water off of the drywall, but it will not allow the water to evaporate creating a wet situation which will, in time, manage to saturate the drywall.

So don't do it!

Blue bolts are expensive. Oh and keeping the foam in place and... Wow and...

So don't do it!

Here is what people do...

  • Blue bolt 3/4" furring strips to the drywall. Better yet, use 2x2s.
  • 1" drywall bolt the 1/2" drywall to the furring strips. Better yet, use 5/8 drywall to keep the drywall flat where you will be missing a top and bottom plate and use 1-1/4 inch screws to attach it to the 2x2s.
  • Do not allow the drywall or the furring strips to directly touch the floor.
  • Install floor trim to cover the gap between the floor and the drywall.

This creates an air gap so that the block can breathe.

Remember: The block needs to breathe or it will become wet. So don't create a bottom or top plate and don't let anything touch the concrete floor save the trim on top which will probably be 3/8 off of the floor to allow for carpet.

  • Thank you for the detailed answer. You need to read the long story in the other thread to understand why I will not be able to put furring strips there. Also tis is a wall that is all inside no water there for the last 60y and it won't be any going further, Not even from condensation
    – MiniMe
    Commented Oct 9, 2021 at 22:20
  • 1
    Concrete is a moisture sponge. The water evaporates off of the block faster than the block sweats. All concrete sweats. If you are not worried about sweat, then why put anything between the drywall and the block at all? Seriously, how about just using a sheet of plastic?
    – Paul
    Commented Oct 9, 2021 at 22:30
  • I need to make up the 1/16 or 2/16 difference between the old and the new drywall -I am not worried about humidity there
    – MiniMe
    Commented Oct 9, 2021 at 22:46
  • A table saw will allow you to create 1/16 or 1/8 inch furring strips.
    – Paul
    Commented Oct 9, 2021 at 22:53
  • Yeah I do have a table saw and wood but I was trying to avoid that
    – MiniMe
    Commented Oct 9, 2021 at 23:00

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