We’re putting a bath in the basement of our townhouse. We’re building a shower against one of the “exterior” walls (it’s shared with a neighbor, not the great outdoors).
I’m wondering–could we avoid firring out that wall, to save the inches in the shower, and somehow put tile onto cinderblock? If so, how would we prep the wall to smooth out the variations between cinderblocks and mortar?
Any help/advice would be great. Thanks!
Melissa
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Replies
Greetings Melissa,
This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.
Perhaps it will catch someone's attention that can help you with advice.
Cheers
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Parolee # 53804
I would put a coat of cement plaster on the wall and smooth out the surface with this. If the shower was going to see a lot of use or if the adjacent walls needed it, I would put up kerdi membrane over this to keep water out of the wall. Otherwise I would just put up the tiles over the cement plaster.
It depends on the type of tile whether you would even need to smooth anything out much.
My larger concern would be the joint between the exterior wall and whatever intersecting walls would joint in the shower. Odss are that they would not always move at the same rate, so that corner joint would end up leaking.
So I would apply cement board to all shower surfaces, with a good caulk on that inside corner.
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Just did some tile replacement on a tub surround where the tile was set directly on the CMU. It took a lot of work getting them off, even the tiles that were cracked along the bottom course. Had to chip off all the thinset with an electric chisel. But we had to install 1/2-inch tile backerboard to bring the tile up and over the tub lip. Used thinset and concrete screws to install the backerboard, then Redguard over the backerboard before tiling. The backerboard provided a smoother surface to tile on.
So it's 2-to-1 for cement board/backer board--and I can put this directly on the cinderblock with thinset + screws? That would take less space than the whole firring extravaganza.
Melissa
I believe Kerdi can be applied directly to a masonry wall. Check out the John Bridge forum or the Schluter site for more info. Using Kerdi will eliminate the need for cement board backer, will more effectively keep moisture out of the block wall and will help promote better drying out of the shower between uses.
I'm surprised the Kerdi-Corps in this forum weren't all over this one! ;-)
Mike Hennessy
Pittsburgh, PA
I tiled a few showers in a provincial park near where I live about 12 years ago. They were concrete block, I tiled with porcelain tile and thinset directly on the concrete block. These showers get used almost continously for most of the summer then when the park closes in October they are out of commission all winter until spring.( We have cold winters with plenty of snow).
The showers are basically as good today as when they were new. I don't think you could get much better a substrate than concrete block.
Have a good day