Tile – Best method to tile over concrete block with drywall glued over it

tile

We're adding a shower to a half bath and during demo discovered drywall has been glued to the concrete block wall. Four feet of this wall will be used for tile in shower. Our Tiler says he can use Kerdi waterproofing but the inspector says we have to use furring strips over the drywall and 1/2 inch concrete board over that. Then tile. My question(s): 1) Do we need to install some kind of vapor barrier in this scenario? 2) Can we use insulation board between fur strips and if so, foil facing tile or away from tile? 3) Any other suggestion to do this per code?

Thanks!
DParker

Best Answer

There are not many options to resolve this properly. So I will address your questions first.

1) Do we need to install some kind of vapor barrier in this scenario?

The current best practice is to place waterproofing over the backer board and just under the tile. (ie Kerdi waterproofing)

2) Can we use insulation board between fur strips and if so, foil facing tile or away from tile?

The answer is no and for the same reason no vapor barrier is to be used behind the backer board. The wall cavity should be able to breath and allow any moisture to evaporate.

Updated: Based on finding out it is a basement

So my answer to you is: As mentioned by Ed - Spray with water to soften the drywall and it should easily come off to the paper.

Inspect and choose best method of removing glue: if it was glued unevenly. Maybe snap lines or draw lines as a layout for furring strips. (no need to do more work than needed)

Fasten furring strips, use backer board, seal (recommended) with (ie. Kerdi waterproofing) and tile over that.

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