I'm in the middle of re-tiling my tub surround (about ready to tile, actually). I tore it down to the studs, then put up a plastic vapor barrier and cement board. The problem is my tub has a 1/2" lip that comes up. I couldn't overlap the lip, so I just put the cement board on top of that, planning to tile as low as the cement board will allow, and then filling the gap between cement board/tile and the tub with caulk.

Is this an acceptable solution? Should I fill that 1/2" gap with thin set first?

Thanks!

I think you would have better luck if you let your tile come down to within a 1/8th inch of the tub. It will look better than the 1/2 at the bottom

What I usually do is put sheets of lattice on the studs to shim it out. Then I put the backer board on top of the lattice down to about 1/8" of the tub, so it's hanging over the tub flange. Since the lattice is thicker than the flange, the backer board doesn't actually touch the flange, which gives you a little "fudge room" if the walls are not perfectly square (which means the flange isn't touching the studs all the way around).

But since you say that you already installed the backer board butted flush with the top of the flange (right?), I would fill in the gap with latex modified thinset.

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Originally Posted by dmozingo

I'm in the middle of re-tiling my tub surround (about ready to tile, actually). I tore it down to the studs, then put up a plastic vapor barrier and cement board. The problem is my tub has a 1/2" lip that comes up. I couldn't overlap the lip, so I just put the cement board on top of that, planning to tile as low as the cement board will allow, and then filling the gap between cement board/tile and the tub with caulk.

Is this an acceptable solution? Should I fill that 1/2" gap with thin set first?

Thanks!

I think you would have better luck if you let your tile come down to within a 1/8th inch of the tub. it will look better than the 1/2 at the bottom

What I usually do is put sheets of lattice on the studs to shim it out. Then I put the backer board on top of the lattice down to about 1/8" of the tub, so it's hanging over the tub flange. Since the lattice is thicker than the flange, the backer board doesn't actually touch the flange, which gives you a little "fudge room" if the walls are not perfectly square (which means the flange isn't touching the studs all the way around).

But since you say that you already installed the backer board butted flush with the top of the flange (right?), I would fill in the gap with latex modified thinset.

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If I fill it with thinset, I wouldn't really have anyway to stop it from butting up with the tub, leaving no gap. Would that be OK?

What you could have done was rasp the back of the cement board the thickness of the lip then it wouldn't bulge out on you.

You'll be fine butting the lip w/ the cement board. Seal the seam where the cement board meets that tub lip with caulking. Then you can trowel thinset over that gap with a layer of mesh tape. Your tile will span that gap so no need to worry. Leave a slight gap where the tile meets the tub so it can be caulked. You will get grout in that joint but you'll still need to grout it.

All your flat and corner seams should be meshed taped prior to tiling with mesh tape and the thinset you'll use to adhere the tile with. This can be done the day before or while your tiling.

I've butted the tub lips and sealed the seams on a number of tile jobs with no problems.