Tiling Over a Bathtub Lip

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Old 12-28-10, 10:40 AM
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Tiling Over a Bathtub Lip

I'm going to be installing new tile in a bathtub/shower. As I was told to do, I ran the Hardiebacker to just above the lip of the bathtub. Someone in Home Depot told me that instead of filling the space below the Hardiebacker with mortar, I should instead fill it with Silicone Caulk. I've also read this on several other forums. But I'm still puzzled with how I will install the bottom row of tile. I want the tile to lay over the Silicone Claulk, because otherwise I would a pretty big gap between the tile and the top of the bathtub, and it just wouldn't look right.

Should the bottom of the tile simply hang over the Silicone Caulk, not being affixed to it in any way? (would seem a bit precarious to me)
(or)
Should I apply a thin layer of mortar over the Silicone Caulk to give the bottom of the tile something to adhere to? (would seem to defeat the purpose of using Silicone Caulk in the first place)
(or)
Should I wait until I'm actually tiling to apply the Silicone Caulk so that it will bond with the back of the tile? (seems like this process would be more difficult for applying the caulk)



 
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Old 12-28-10, 11:02 AM
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Start your first row just about less than a full tile above the tub edge by using a level straight edge tacked to the wall. After you finish the wall, install the bottom row. You may have to cut the bottom row, which is normal, but it will give you a custom finish all the way down to the tub edge. Use your silicone along this seam. It won't hurt to have the tile extend below the cbu at all.
 
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Old 12-28-10, 11:02 AM
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Typically the studs would be shimmed out the thickness of the tub flange and the CBU installed overlapping the flange. Another option would be to rabbet the CBU (a PITA) to fit over the flange.

If you don't want to rehang the backerboard, I would seal the gap and allow the tile to hang down until it is just short of the tub and seal that gap with caulk.
 
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Old 12-28-10, 12:24 PM
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I see the problem. Thanks Wayne for slipping in that clarification. Yes, the cbu should be removed, the studs shimmed out and the cbu reinstalled over the lip down just short of the tub. THEN you can tile as I had described. It looks so smooth a transition, I missed the lip. Like Wayne said, you could extend the tile over the lip with no ill effects, silicone the bottom.
 
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Old 12-28-10, 03:53 PM
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If the tile is big enough, say 4x4 or bigger, you can install the tile over that gap. If the tile is smaller, you may have issues. Did you install a vapor barrier behind the cement board, I don't see one. Is that joint compound you used over the screw heads?

As has been mentioned, it would have been better to fir out the studs with 1/4" material so that the board could overlap the flange. If you are using hardibacker, you could have also done what Wayne suggested, and notched the hardi so that it would overlap the flange and not bulge out. Just about impossible to do with regular cement board though.
 
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Old 12-29-10, 08:18 AM
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I appreciate the replies. I didn't feel that shimming out the studs was a good option because then I would've either had to tear off the Sheetrock on the walls beyond the shower and shim those studs as well, or be left with a situation where those walls would be offset from the shower walls. I wanted a smooth wall transition from inside the shower to the outside without having to gut practically the entire bathroom.

With me being a novice at all this, I don't think I could've successfully notched the bottom of the hardiebacker. The groove would've been so deep, I'm pretty sure the remaining thin layer of hardiebacker would've ended up breaking off. An any event, I'm not planning on ripping out the hardiebacker, so I need to deal with the gap where the flange is.

There is a vapor barrier, but it's currently laying just behind the lip. Another person at a home depot who told me to do it that way. I can pull it out and have it laying over the lip if necessary. I'm just concerned how well the caulk will adhere with the plastic directly behind it.

By the way, Johnny, that's thinset over the screw heads, not joint compound.

It looks like I'll do what Wayne suggested and seal the gap with caulk and allow the tile to hang down over the flange and seal the remaining gap with caulk. My only concern is that my kids will smack something into the bottom of the tile. With only silicone caulk behind it, seems like it would be prone to cracking or completely breaking off there.
 
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