I am remodeling my 1950s home and I have exterior walls made out of masonry bricks (cinder bricks). The interior of the bricks has been painted many times over. I've been given 2 basic recommendations from contractor friends and I thought I'd ask the group.

First off, bricks are porous. I can tell the previous homeowner had issues with this. I'm planning to roll 2 coats of Redgard on the inside of the walls and the outside of the walls will be vapor barriered and stuccoed. Then, my choices are to either place greenboard directly on the Redgard-coated walls or to hang furring strips and then place the greenboard.

I have a couple things to spell out. 2 of the rooms in play are already pretty small. The thought of losing 4 inches of width in these rooms isn't a great proposition (2x 1.5" 2x4s + 2x 1/2" drywall). So, how thin of a furring strip could I get away with?

I live in Southern California, so insulation isn't hugely important for outside cold weather, but should I use furring strips so I can insulate to keep cool air in? Furring strips are also good for running wire, but I don't have a need there.

Any thoughts on my plan? Any thoughts on greenboard on sealed bricks vs. greenboard on furring strips?


  • I'd give serious consideration to straight-up plastering (as in troweling it on the brick), given your parameters. I guess swimming pool folks still do that sort of work if not looking to DIY it.
    – Ecnerwal
    Sep 29, 2017 at 3:45

1 Answer 1


According to this link, you can fasten drywall directly to block.

Personally I would use 3/4" furring strip and fasten with tapcons - or build a wall so I have wood to screw into. Since losing space is a concern here, adhesive and drywall screws or drywall nails should be enough to fasten the drywall.

  • 2
    I agree about the 3/4" (1x2) furring strips, but you'd have to use concrete screws to go without furring strips.
    – isherwood
    Sep 28, 2017 at 18:57
  • Would you put these furring strips up and then put something like a Redgard over them or would you put the furring strips on top and drill through the Redgard?
    – pennstump
    Sep 28, 2017 at 19:10
  • I feel like redguard would be overkill. A polyethylene plastic sheet or a similar moisture barrier would be fine to install underneath the furring strips. It would also save you money in materials. @isherwood That's what I was thinking too but the answer in that post above seemed well received. Sep 28, 2017 at 19:29
  • 3
    I can tell you from a whole lot of experience that drywall screws will mostly snap off if driven into block. Heck, they break sometimes if you hit a knot in wood. Also, they're not corrosion-resistant. I'd want something that's coated.
    – isherwood
    Sep 28, 2017 at 19:49
  • UK practise is to use adhesives and no screws ("dot and dab"). Battens and screws are only used for very uneven walls or where extra insulation is needed. Sep 28, 2017 at 20:47

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