Shower Tile Question

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Thomas K

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I think I have messed up. I hired a guy to tile my shower area. He installed 1/2" Durock on walls, 1/4" Hardieboard on floor, even in cast iron tub area. He is almost finished with the alcove and floor. He even tiled where cast iron tub will sit. He did not tape the wall joints, but did on the floor. He installed no RedGard.

He installed my expensive 12 x 24" porcelain tiles with white mastic. Did a good job, but I'm wondering if I am going to have water problems.

Can the grout be sealed and this setup be okay? I hate to get rid of the tile guy, but I'm wondering.

Thanks for any replies.
 

Jadnashua

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On all of the mastic buckets I’ve looked at, there is a maximum tile size limitation, so unless there’s a new one out, mastic is not approved for a tile that large. The reason why mastic survives in a bucket is because the lid prevents it from drying out. Now, some moisture will be absorbed by the cbu, but until that happens, it will remain flexible, and tile doesn’t like when it can move!

Something like RedGard is not a requirement to meet industry standards in a tub surround. You do need a vapor barrier behind the cbu or waterproofing on top of it, but not both.

Sealing the joint between the tub and the walls is most easily accomplished by running the vapor barrier behind the cbu, and lapping it over the tiling flange, then leaving a slight gap between the bottom of the cbu and tile to the tub surface and caulking that.

Wall to floor joints are expected to move, and only need to be waterproofed in a shower.

Neither tile nor grout is considered waterproofing...they are the decorative/wear surface. A wall in a shower does not need to be waterproof as most all of the moisture is expected to just run down the surface (hopefully, unobstructed!) and to the drain, and what may penetrate slightly, should dry out in between uses. A shower pan, though must hold water and be waterproof, but again, that’s not the tile.

When installing the cbu on the floor, did he use any mortar underneath? All of the manufacturers require that (and mastic doesn’t cut it there!). if the panels were just screwed to the floor, that’s against the manufacturer’s instructions and would be a reason to require fixing. Tearing up a large tile like that can be messy, and you may not be able to salvage much of anything. If you do, the mastic will wash off if you soak it first, scrape off the softened mastic, and scrub it clean. The labor to do that may mean it would be cheaper to buy new tile.

While mastic is approved for use on a shower wall, none that I”m aware of are approved for use on the pan of a shower, but it sounds like you’re talking about a tub alcove, so mastic, if the size of the tile was within allowances, could be used. Generally, it ends up more expensive than a decent cement-based thin set, but that takes more time and cleanup since you can’t just put the lid back on once you’re done and there’s no mixing.

Check out www.johnbridge.com for help with tiling.
 

Thomas K

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Durock on walls behind tile was not taped at seams and corners, nor mudded, and this will be used as a shower by wife and myself. No waterproof membrane behind CBU nor Redgard on top. He wanted to tile entire area, set tub in, and just caulk where tub met tile. Just asking for water intrusion if you ask me. Oh, well. I'm having another (reputable) tile guy look at it this evening. Will post photos (before and after) when I can. He did use mud between Hardieboard and subfloor.
 

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The installation instructions call for the use alkali resistant tape on the board seams, so not following the manufacturer instructions is a hit. Changes of plane, not necessarily, but on the walls, yes, those should be tape3d. Whether you put the tape up then thin set over it then wait to install the tile, or do it all during the tile installation doesn’t really matter except on a floor that needs to be waterproofed.

But, again, I suggest you read the spec sheet on the mastic used, and I’d be surprised if it was allowed on a tile that large. To stabilize, mastic needs to dry out first. A thin set will cure even if it is wetted, but some modifiers also need to dry, but most do not.

A tub without a tiling flange, just relying on caulk to prevent water from getting through is a mess waiting to happen. Tiling to the floor, and underneath the tub (unless it’s something like a claw foot that would be exposed), is just a waste of materials.
 

Thomas K

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I had someone who knows that they're doing inspect it this evening. He told me thinset made for heavy tile should've been used instead of mastic, and that seams should've been taped and mortared. We started pulling on the tiles and they came off the walls with just a little effort. There was almost no mastic sticking to the tiles themselves. I can probably clean off the remaining mastic and reuse some of these tiles. He did say floor tiles were okay, but I needed to remove the ones where the tub will sit.

He told me to remove all of the CBU and start over; said bathroom needed to be drywalled first, as well as set tub and shower valve, or have it done, and then worry about waterproofing the tub area.
 

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You don’t want drywall behind your cbu unless you’re using Kerdi on top of the drywall as it’s the only one approved in a wet area over drywall.

When setting any tile, but especially a large format one, you need to burn some thin set on the tile first. In a shower, the industry standard calls for 100% of the edges and at least 95% of the surface of the back of the tile to be covered in thin set (note, thin set is a method, and both mastic and a cement-based material qualify).

I’d still look at the specs on the mastic used...my guess is that it isn’t allowed on a tile that size. If they didn’t get good coverage on the walls, what makes you think they did on the floor?
 

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Schluter doesn’t allow any mastic on their products, so keep that in mind.
 
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