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My wife and I have a basement bathroom that I gutted: back in 1980 someone decided to put tile directly on drywall and not properly seal anything, with the obvious moldy result. So I ripped it down to studs and concrete.

My question is about the shower area. This is in the northern U.S. for code purposes.

The attached picture shows the area. The wall with the window is obviously an exterior wall. The wall on the left is an interior divider wall. The space on the right will be framed out with cement board and tile on it.

What is the proper way to seal the cinder block walls considering this is a shower? We were going to put on two coats of Drylok, but this does not actually seal anything. If we put cement board and furring strips on top of the cinder blocks, do we even need to seal it? We are not completely sure if we want to spent the time, effort and money on tiling the whole thing, so I would appreciate advice both for the tile route as well as bare cinder block walls. At the very least though we will be building a base including a lip around all three walls and the open area so water does not go wandering out of the shower.

Edit: my wife is convinced we need to paint with Drylok and then epoxy floor paint (but on the walls). Is this a good idea?

Picture of the shower area

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We ended up using a heat gun to remove the linoleum floor tiles (some cracked right off) so we have bare cement to attach tile. We then used a cement cleaner on the walls and floor to get the nastiness up, and put a coat of Drylok on the walls. That stuff was like glue, one coat easily did it. Now we are on to the next part of the project... – Snowman Apr 9 '14 at 1:10
up vote 1 down vote accepted

Drylok is suppose to be water resistant up to 2 or 3 PSI when used on an exterior wall. So I guess, practically speaking, you could use a coat or two of drylok on the walls. keep in mind, the oil based drylok finishes to a glossy smooth surface and the latex based dries to a very rough finish. This may have changed in last couple of years, however, since the last time I used latex drylok was about 3 years ago. If the floor tile is secure, doesn't leak now, you could use an epoxy sealant as long as you clean and prep the tile. Id test a small area if possible to be sure it sticks well. there are a lot of sealers out there, so be careful selecting one that says it will stick to your type of tile.

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I thought Drylok was not an actual sealant, but we picked up a 5 gallon bucket today and it claims that it is. This particular bucket says it is good up to 10 PSI, which should be adequate for a shower (there is a more expensive one good to 15 PSI). – Snowman Feb 22 '14 at 20:48
The PSI rating is for hydrolic pressure from water in the ground exerted on a foundation wall for example. Your shower will have 0 PSI – shirlock homes Feb 22 '14 at 20:56

The cinderblock walls are fine. Its the 2 other walls you need to worry about with sealing the wall to floor. I always talk my customers into shower pans so i dont have to deal with that.

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I like the shower pan idea. That is going to involve redoing the drain a bit, but not a huge job. – shirlock homes Feb 22 '14 at 18:11
using a shower pan also means you would have to fur or stud out cinderblock walls and add cement board – Justin K Feb 22 '14 at 18:15
Right now we are going to build a shower pan with tile. The question is how far up the walls does it go. I say fur/cement board/tile to the top of the cinder blocks. My wife is not so sure. – Snowman Feb 22 '14 at 20:45
Also, the wet wall on the right (there is no plumbing there yet but there will be) will be tiled six feet up regardless of what we do to the other walls. – Snowman Feb 22 '14 at 20:49
It doesnt matter if it goes up 6 feet or to ceiling. It is just a design preference. I would bring the furring strips all the way up and tile to ceiling or put in drywall above 6'. It would not look right to have tile go up 6' then a 1.5 inch jog back to ciderblock. – Justin K Feb 22 '14 at 21:11

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