cut edge tile paint, trowel

[stollie]

Hi, I'm working on a 3 wall tub/shower project, I stripped the walls down to the studs, put up the backerboard and taped & thinset the backerboard. I used roofing felt behind the backer on the 1 inside wall. On the 2 other walls I have insulation with vapor barrier, not a separate vapor barrier, but built into the insulation[50+ year old mineral wool insulation]. Before I do the tile install, I would like to know if the insulation vapor barrier is adequate for this installation? Thanks, Dave

[jgleason]

Hi Dave,

No, I don't think the insulation vapor barrier is a good idea. Neither is a double vapor barrier either so here's what I would have done...

1. Make several large slits in the insulation vapor barrier, rendering it useless.
2. Cover with 6 mil poly sheeting (15# roofing felt also works but I like poly)
3. Install backerboard and tile.

[stollie]

Thanks Joe
That would mean opening up about 3 joints and taking down the backerboard. How would I refill the joints when reinstall the backer, thinset or silicone?
Thanks again, Dave

[sean riha]

you'll need to re-tape and thinset those joints if you want it done right.

[stollie]

Hi Sean
Thanks for your reply. How would you remove the thinset and tape? or do I need to start over and get new backerboard?
Thanks, Dave

[sean riha]

which backerboard did you use? sometimes i've been able to pop tiles away from hardibacker a day or two after they have set. it pulls a bit of the top layer of board away, but it really no big deal. 'maybe' you'd be able to pull the tape/thinset away from the board. give it a shot i guess. if it's impossible then might want to redo them b/c adding another layer of tape and thinset to the one you already have may create a big speedbump if you're not careful. so if you are able to pull it away you're good, and if you think you can go over the top of it and feather the thinset out real nice and gradual and then be cognizant of that little bump while you're tiling you may be able to get away with it.

[john2777]

Why not just use Redgard over the existing backerboard and then tile. Redgard is a very good vapor barrier and should keep any moisture from getting through the backerboard. Or maybe just use Redgard on the walls with the insulation barrier. It would be a shame to have to rip up the installation if there was some acceptable alternative.

[cx]

Welcome, Dave.

I'd say the best compromise would be the last suggestion from John2777:

Or maybe just use Redgard on the walls with the insulation barrier.

I'd just extend the Redgard a couple inches onto the wall that already has a moisture barrier behind it. And you need to do the RedGard precisely as prescribed by Custom.

And you still have the "moisture sandwich" consideration on those wall with that method. I'm assuming your insulation backing is Kraft paper and given it's age and the usual method of installation, you might not have as much problem as with some other materials. Not the best situation, but not the worst, either. These are exterior walls?

The RedGard isn't inexpensive, but I think you'd end up buying new CBU if you try to remove what you have to install a proper barrier behind. And you'd have a problem in the corners anyway.

You can always claim you read the Hardi instructions and they said you didn't need no steenkin' moisture barrier anyway. Might work for peoples who don't know better and don't read these forums.

My opinion; worth price charged.

[stollie]

Hi
Thanks for the suggestions. Only one wall is an outside wall, the other one was an exterior wall, but is now an interior wall. I was thinking, maybe I could unscrew the Durock cement board,which would only leave the thinset seams holding it. The 2 side walls have only 1 horizontal seam, about 33" long, so it should only be attached to the vertical studs. Would the thinset seam hold together? Reinforce it with 2 x 4s vertically? Does anybody think this would work? As for the back wall, I have 2 short horizontal seams and 1 vertical seam on a stud. I'd prefer to save all of the backer, but if I had to sacrifice 1 or 2 to do the job right, so be it. I've seen there is a sale on backerboard, do not know if it's Durock, but it's about $8 for 3 x 5. What kind of price for Redgard, about 50 sq. ft.?
Great site, I wish I had found it earlier.
Many thanks, Dave

[cx]

Again, Dave, trying to take down only the two side walls still leaves you no effective way to provide a barrier behind the CBU at the vertical corners, and that's one of the most critical places in the construction because if you have cracks in the CBU joints, that's the most likely place for them to occur.

If you're gonna take down the CBU, I'd take it all down and start over.

My opinion; worth price charged.

[stollie]

Hello again,
Removed all the backer, cleaned up the thinset on the backers with a grinder, stapled the 6 mil poly to the studs. Questions, should I seal the staples and around the plumbing? They recommend siliconeing the poly over the tub flange, wouldn't that trap the moisture? Also, I'm thinking of putting some non-expanding foam behind the tub on the back[exterior]wall,I live in wisconsin and can feel the cold thru the wall, would there be any problems doing this?
Thanks, Dave

[cx]

All the moisture that reaches the poly barrier should be on the inside, Dave. Attaching to the tub flange should not interfere with that.

That said, I always let my poly drape loosely several inches into the tub when I do mine, then you can install the CBU (I would be installing mud) over the poly and only trim the poly after the walls are installed. It never goes anywhere after that.

No need to pookey up the staples (shouldn't be but a few, anyway) or other penetrations. Just cut them as closely as possible to the pipes and such. Remove the plastic plaster ring from the valve before you install the poly and then replace it over the poly = smaller hole.

Whatever you can do in the way of insulation behind the tub and walls is a good thing, far as I'm concerned.

My opinion; worth price charged.

[stollie]

Hi again,
Just about ready to tile, on a cut tile, where the edge has been slightly rounded off, what type of paint should you use? I've heard some type of epoxy paint, I need an dal tile arctic white and a black, any suggestions? Also my supplier recommended a 1/4 x 1/4 v-notch trowel, which I could not find except in plastic, asked them about the same size u-notch, and they said that would be ok. Would that be ok? 13x13 and 6x6 tiles
Thanks, Dave

[stollie]

Hi again,
Just about ready to tile, on a tile that has been cut and smoothed, what type of paint could you use? I've heard some type of epoxy paint, I need an dal tile arctic white and a black, any suggestions? Also my supplier recommended a 1/4 x 1/4 v-notch trowel, which I could not find except in plastic, asked them about the same size u-notch, and they said that would be ok. Would that be ok? shower/tub wall, 13x13 and 6x6.
Thanks, Dave

[stollie]

Picked up some negro marquina to use as shelving and an accent strip around the tub/shower. epoxied 2 pieces together for a 3/4" thick shelf, rounded off the edges, sanded the top, bottom and outside edges up to 800 grit. How do I get it to shine? I was thinking car polish & wax. It's advertised as marble, but from what I've read, it is limestone. Should it be sealed or impregnated before polish/wax? Thanks again