Do I need backer board on walls?

12 years ago

I had asked the tub surround have cement backer board on the walls so I could tile partially up (like up to window) from the deck. Add it to the list of things that didn't get done when the house was built.

Now I am ready to finish the master bath (starting with floor so we can use the shower and set the toilet, tub will be done sometime later this year) and am wondering if I can tile over the painted drywall in the tub surround. Bathroom person at Lowes told me if I'm using larger than 8" square tiles I will have problems with drywall (not even green board). I was planning on using 12" square tiles topped by 2-3" bullnose. I want to do all the demo/reconstruction now before I start finishing anything.

Thanks!

Featured Answer

PRO

Avanti Tile & Stone / Stonetech

12 years ago

Inasmuch as there is no shower there, it is perfectly acceptable to "Tile Away." Most installations that I do of this type seldom tile higher than the bottom of the window, but, your house, your choice.

Forget Lowe's advice. Simply scuff up the area to be tiled with sandpaper and install. Since this is, strictly speaking, not a "Wet Area," you can use a Type II mastic for the walls.

Are you also tiling the skirt and face? Would have been nice to do so before installing the tub. Always better to tile the platform and then drop the tub in on top of the tile. Anyway, just put up drywall on the face and possibly a cement board on the flat surface,thinset and screw it down then tile it. Tile size is not an issue on any of this. A 12" mosiac tile weighs about the same as a full 12" tile.

Where the wall meets the horizontal surface, space the wall tiles about 1/8" up off the flat tiles and use a silicone, colour-matching caulk there.

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Comments (9)

2ajsmama
Original Author
12 years ago
This was a modular house, I asked that the tub be shipped loose so I could tile then drop it in, but they foamed it in place. So I have to tile around it. They did put 1/2" Durock on the deck, but nailed it in (and didn't tape the seams, but I can do that).

I pulled the cement board off the face/apron, plan on putting wood there. I had a whirlpool in the last house, bought unfinished cabinet doors built to size, that worked out well. I don't know if I'll do doors, sliding panels, piano hinge, or just T&B wainscot here but will do something wood.

Thanks - I was thinking I'd rather have 12" tiles than something smaller, the less grout the better (though I may put in some mosiac as accents). What grit sandpaper? Will mastic be better than thinset? Since I have to buy thinset for the floor and the tub deck anyway?

Oh, BTW, will you comment on my faucet/grab bar placement thread? Even with pulling the `1/2" cement off the face (and may pull the spacers off the 2x4s too), putting 3/4" wood back on will still make it a bit of a stretch with a 20" high deck, 3" ( or was it 2"?) high tub rim, and only 30" inseam. I'd like to cut the deck back another 3-4" but it's probably not worth trying to do it around the tub.
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dorry, As you know, water can get past the tile and grout. Once it does, it'll hit the tile backer board. Cement board is an excellent tile backer board because it is not negatively affected by water. Wet it, dry it, repeat the cycle...and in 50 years the cement board will still look like cement board. Unlike a gypsum board, which will slowly turn to mush with repeated wetting and drying cycles. Now cement board is not waterproof. Wet it and water can pass through it. That's why you need some sort of drainage barrier in the wall. It's often done by stapling 6-mil polyethylene plastic to the studs, then lapping the bottom edge of the poly over the tub flange. Any water that gets past the tile/grout and through the cement board will hit the poly. The poly prevents the water from getting into the framing bays. Most of the time all will be well. The tile and grout shed 99.99% of the water down the drain. Any minor imperfections in the wall, the cement board might get a little bit wet. But think of the cement board as a sponge, it can hold a bit of moisture in it's pores. When the shower is not in use, any moisture that got into the wall usually evaporates back out of the wall. No big deal, no damage. Now if you had a damaged wall...bad grout, a cracked tile, etc...then you could get more water into the wall. If thee is more water getting in than can get out via evaporation, then the poly will stop the moisture from getting to the house's framing. It'll hit the poly and flow downward, over the tub flange, and back into the tub if weepholes were left in place. Poly is one type of membrane. Anther is a topical membrane that can be used on the face of the cement board. RedGard, Hydroban, etc. They get "painted" on the cement board, then you tile on the membrane. But as Bill wrote, any partial repairs leave you in an conundrum of sorts. Not sure if this is worth anything, but you mentioned greenboard. Greenboard as a tile backer in a shower has been a known poor building practice for decades. It has been an outright code violation since January of 2006. That's no help to you now, I know that. The big concern to address with your worker is the top horizontal seam of the repair. You'll have a seam in the tile backer, topped by a "seam" or grout line in the tile layout. A seam over a seam is an excellent point for flexure failure (cracks in the grout) and eventual water intrusion into the wall. Any issues will be compounded by there being nothing behind the tile backer to contain any water that gets back there. At a minimum, I'd remove the cement board and try to slide poly up behind the bottom edge of the existing tile backer, between the bottom of the existing tile backer and the wall studs. Even an inch will help. Enough to get some protection behind the eventual double seam. Then drape the poly down over the tub flange. Reset the cement board over the poly.
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PRO
Avanti Tile & Stone / Stonetech
12 years ago
Any medium grit sandpaper is just fine....Just rough up the surface.
David
12 years ago
If the wall is not completely flat, irregularities in the grout lines , one tile edge being higher than another, could be quite visible when large format tiles are used. In such a situation, the best solution is to float the wall (i.e. - chicken wire, mud, tar paper backing).
PRO
Avanti Tile & Stone / Stonetech
12 years ago
Sure, that's the best of all possible worlds....but it does raise the surface of the tile quite a bit and require mudcap for the edges. If the walls are flat within reason...you should be able to adjust with thinset...or use the "dot" method.

And yes, thinset is preferable if it's there...
2ajsmama
Original Author
12 years ago
Well, I haven't noticed any humps (or cracks) in these walls (though there are plenty of other places in the house that have humped studs), I will take the level to the walls before I start tiling. I'm afraid the deck isn't level though, and I can't do anything but "fudge" with thinset since it's nailed in.

I've got 1 spot on the deck right up against the linen closet (left as facing the tub) wall, there's a glob of construction adhesive. I figured all I can do is try a sharp chisel? More on the plywood subfloor, I can try to scrape that off, but at least there I assume I can go over the 23/32 plywood with backerboard, or use SLC after putting the radiant heat down. Just have to caulk all along the walls, the tub deck, and the seams in the floor before using SLC.

What do you do around the closet flange before SLC?

And what's "dot" mthod (backbutter?)?
PRO
Avanti Tile & Stone / Stonetech
12 years ago
The "dot" or "spot" method has been used for out-of-plumb walls successfully. One uses a margin trowel to spot lumps of thinset....usually 6-9 on the tile back and adjust on the wall with a level and rubber mallet. In this way, you can set them at varying distances to the wall as needed.
Billl
12 years ago
If you are concerned about moisture, they sell paint-on style waterproofing membranes. They are designed for showers etc. That would be complete overkill for a soaking tub, but if you've got kids, it is cheap insurance against water damage.
2ajsmama
Original Author
12 years ago
Kids shouldn't be using this tub (well, I might let DD when she's a teenager). That's why this one is a soaker - the kids were using the Maax airpool more for bubble baths than I was ;-) Coulda used it today - sore back since Sunday AM (stacking wood Sat, bending over bench starting seeds Sun and Mon).

Back right corner by deck the wall is sunken (bottom of drywall tilted back toward exterior) so I need to build out a couple square inch area. Do this with joint compound, thinset or ??? Not sure what David meant by "mud".

Oh, and the deck is 1/2" or 3/4" plywood with 1/2" Durock nailed to it. I'm assuming there was no waterproofing. I can access most of the tub (excepting the side along the exterior wall) from underneath. Should I apply one of those paint-on waterproofing membranes, an exterior polyurethane (I have used Sikkens Cetol on my front door) or latex paint to the cut edge of the plywood around the tub cutout? Or is that overkill for an adult-only soaking tub?

Do I need backer board on walls?

Avanti Tile & Stone / Stonetech

Comments (9)

2ajsmama
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Do I need backer board on walls?

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