Waterproofing Walls to Bathtub


Old 01-14-13, 09:46 AM
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Waterproofing Walls to Bathtub

I am having a plumber putting in a new Sterling Vikrell tub on top of a bed of motar.

I will be doing the tiling myself. I have done research by googling and youtube so far. I do know how to do tile but never done it in the bathroom before.

So far from research, I know that I have to put a vapor barrier and then cement boards before I can tile.

The questions are around the vapor barrier.

I know that I am suppose to start from bottom to top and overlap 3 inches. Where the tub's edge, do I overlap it and compound it with roofing material?

Then when I screw the cement board on top of it, I would use joint tape and thinset.

Please let me know if this sounds about right or you would like to share any other tips.

Also, if I use this a waterproof membrane as the link that I provided, would I need to put in a vapor barrier like mentioned above? What is that paper call anyway - tar paper?

RedGard 1 Gal. Waterproofing and Crack Prevention Membrane-LQWAF1 at The Home Depot

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Old 01-14-13, 02:53 PM
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Vikrell is the material it is made of, not the style, so I am assuming you have a lip on the three wall sides of the tub. You should have all your sheetrock removed from the floor to at least where your tile will end. Then apply 6 mil plastic as a vapor barrier (not roofing felt). I do it a little unorthodoxically in that I allow my plastic to drape down into the tub a few inches. Once the vapor barrier is in place, I apply the cbu with approved screws so the bottom edge of the cbu rests slightly on the tub rim and the plastic is still out and over the rim of the tub. Trim the plastic up about 1/2" off the deck of the tub. This will leave a continuous "drip" should anything bad take place. Use approved mesh tape (not sheetrock tape) for your joints along with thin thinset. If you are planning on a soap cubby, make framing plans early on.

Since your tub rim will be level (hope) you can start your tile about 1/4" off the rim and continue up with that.
Old 01-14-13, 05:32 PM
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I didn't get a finished pix of this, but you can see the 1/8" corrugated cardboard on the tub rim with the tile sitting directly on it at the bottom. Once pulled out, it gives that slight gap serving the purpose of a potential weep area as well as not having to silicone the gap causing a potential mold area. It won't wick as the cbu is a good inch above the bottom of the tile.

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Old 01-15-13, 07:38 AM
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What Larry said, or you could go the redgard way as well. If you decide to use the redgard, don't use the vapor barrier behind the board. Mud and tape all the cement board joints with thinset and alkalai resitent mesh tape. Take the time to get everything nice and smooth. You can sand off any excess thinset. Wipe all the dust off the board. Thin the Redgard by using a 50/50 mix of Redgard and water for the first coat. Apply a second coat undiluted. Apply a third coat if need to get the necessary thickness per Redgard instructions. You can use a good silicone caulk to seal the board to the tub deck before you tile. The idea is to leave no part of the cement board unsealed so it cannot wick water. For large format tile, give the thinset a couple of extra days to cure before you grout.

As a side note, you'll have to either fir out the studs so that the cement board can clear the tub flange or start above the tub flange with the board. If you use Hardibacker you can cut away enough of the back of the board to overlap the flange. Many of the membrane manufacturers tell you that you can use drywall for the walls. I'm not a fan of this but some say its ok.

Another option for waterproof walls is the Schluter Kerdi fabric. You may want to check it out..

Larry, looks like nice work.
Old 01-15-13, 09:29 AM
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If your tile does not extend all the way to the ceiling I suggest locating the cement board/drywall seam a couple of inches below the top of the tile.
You can buy 6 mil vinyl in a floor to ceiling width. It goes up a lot quicker and there would be no seams.
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