My shower walls were moldy because they used regular drywall instead of concerte board, so I ripped the tile walls out down to the studs so I could redo them.
But I now see that the concrete floor does NOT go right to the studs. It has a 1/2 inch "trench" all around it between it and the wall studs. The waterproof membrane in the floor does go under this trench and is flush against the studs.
1] If have no idea why they did this trench. They did have the drywall laying down inside this trench (which I understand is wrong and is probably why it got so wet - the board behind the tile should be slightly raised from the floor). But what is with the trench - why did they do it this way?
2] I'm not sure what to do about it. I will be installing concrete board on the walls now. Someone said I should fill this trench with a bonded topping type product to get rid of it. Otherwise I'll just leave it as an "air pocket". I'm not sure what to do!???
Thanks!
2007-10-23 14:29:04 · 6 answers · asked by sting 2 in Home & Garden ➔ Do It Yourself (DIY)
One more thing... when I ripped the old walls out, I'm worried that maybe I put a hole in the liner somewhere... would it be wise to fill the "trench" with water to verify that it doesn't leak while it's all open, or would it be crazy to saturate it with water? How in the heck would I get all the water out once I've determined there is no leak?
2007-10-23 14:53:59 · update #1
What's with the tile fetish, put a fiberglass unit in and fuhgedabodit.
2007-10-23 16:17:59 · answer #1 · answered by Anonymous · 0⤊ 0⤋
When you install the wall board (Wonderboard, Hardibacker, etc.), it should NOT rest on the shower pan (floor). It should ride about 1/4" to 1/2" above the pan. Even though the wall board is made of a material that resists fungus growth, it isn't meant to be in contact with water because it's porous and will absorb water. That water will cause the tiles in the area to delaminate from the wall board.
When you install the tiles, they should also not contact the shower pan, but should ride about 1/8" above the pan. (That means they'll hang a little below the bottom edge of the wall board.) This gap should be filled with a suitable caulk made specifically for bathroom applications. I use Polyseamseal, and it's great... Water clean-up before it cures. The same sealant should fill the 1/8" gap along the vertical corners of your shower, and around your shower door assembly.
Since I couldn't quite visualize the trench you described, I don't know why it would be there, but it could be to allow expansion/contraction of the shower floor without the floor pushing on the shower walls. Also, since the shower floor is concrete, it's going to absorb some moisture, and it's best if that moisture isn't allowed to wick to the wall studs (because it'll cause the studs to rot), so the gap may serve multiple purposes.
The experts at your local hardware store (Lowe's, Home Depot, etc.) ought to be able confirm what I've told you and give you the advice you're looking for.
2007-10-23 22:03:01 · answer #2 · answered by Jim P 3 · 0⤊ 0⤋
The drywall was probably the 2nd time it was tiled. Originally is probably was dry cement like the floor. So as long at the membrane goes up the wall you can fill that trench in with Thinset (the same stuff you will use to bond the tiles). Then place your backboard a 1/4 off the floor. Fill the gap with silicone caulk before putting up the tile. This will help with any water wicking up the board. Mesh tape and use Thinset in the seams and corners.
2007-10-23 21:52:34 · answer #3 · answered by rob89434 4 · 0⤊ 0⤋
The trench isn't unusual, it's there to accept the 1/2 inch Durock (concrete board). As long as the plastic shower pan liner is intact, you will have a water proof shower base. the pan liner is what keeps the water from leaking. The concrete helps, of course, but it is designed to accept some moisture. Your tile and grout will also help keep excessive water out of the concrete below.
Pan liner plastic should rise at least 4 inches above the floor decking under the concrete poured pan.
2007-10-23 21:39:28 · answer #4 · answered by Dan H 7 · 0⤊ 0⤋
If they had the drywall laying down into the trench then you should be able to have the cement board laying down into the trench as well. The cement board will be unaffected by water and should fill the trench quite nicely. Just make sure you have at least a 3-mil plastic vapor barrier behind it.
2007-10-23 21:33:57 · answer #5 · answered by Anonymous · 0⤊ 1⤋
they did it right
the gap is so they could hold the sheet rock in palce
they should have used green sheet rock
and installed concreate boards over that
as long as the base is ok, just install your boards, and seal them
2007-10-24 00:46:59 · answer #6 · answered by Anonymous · 0⤊ 0⤋