Do I need backer board on walls?

2ajsmamaMarch 11, 2012

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.


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Avanti Tile & Stone (Stonetech)

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.

    Bookmark   March 11, 2012 at 3:53PM
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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.

    Bookmark   March 11, 2012 at 5:33PM
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Avanti Tile & Stone (Stonetech)

Any medium grit sandpaper is just fine....Just rough up the surface.

    Bookmark   March 11, 2012 at 5:43PM
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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).

    Bookmark   March 11, 2012 at 11:26PM
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Avanti Tile & Stone (Stonetech)

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 should be able to adjust with thinset...or use the "dot" method.

And yes, thinset is preferable if it's there...

    Bookmark   March 12, 2012 at 2:51AM
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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?)?

    Bookmark   March 12, 2012 at 8:08AM
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Avanti Tile & Stone (Stonetech)

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.

    Bookmark   March 12, 2012 at 12:00PM
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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.

    Bookmark   March 12, 2012 at 3:08PM
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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?

    Bookmark   March 12, 2012 at 8:39PM
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