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SWB04 01-22-2015 12:10 PM

Shower/Voids behind tiles - How much of a problem is this?
 
2 Attachment(s)
Hi Folks,

The second contractor just completed the bathroom travertine installation. They pulled a tile at my direction to raise the shower head location 6", and this is what I found (see picture). How much of a problem is this, and what do you recommend I do now?

I've been concerned with voids I saw at the edges of the installed tiles throughout the installation. When I installed travertine, I floated 1/2" of mortar and back-buttered perhaps 1/4" of mortar as well. The result was messy - lots of excess mortar coming out the sides, and setting the tiles took a lot of time. I watched this guy install by only filling holes in the back of the tile, putting down a 1/2" notch on the floor (more at some points, to fix uneven spots in the sub-floor), twisted and then set the tile. He'd work set four tiles, then add spacers and level the tiles. His method was much quicker and less messy, but it seemed to leave voids at the edges. He may have filled these when setting the next tile, but I confess I wasn't watching him enough to be sure. The 18"x18" tile we pulled had good coverage (and took a fair amount of chiseling to remove).

Bottom line is, all tiles tested with a "tap" test seem solid, but I found this void (saw blade demonstates that it continues all the way to the CBU). I'm concerned that water will gather behind the wall, and in particular, in the shower niche, that at best the tile will remain wet and grow mold, or at worse, the water eventually damages the mortar or penetrates the wall.

Is this kind of variance in the mortar filling within standards, or am I being too picky here? What should I do now?

Thanks again.

cx 01-22-2015 12:37 PM

Scott, best to keep all your project questions on one thread so folks can see what you're working on and what's been previously asked and answered.

Best I can tell you've never determined that there is any moisture barrier behind your wallboard and that niche appears to be one of the few places with a waterproofing membrane applied, albeit a bit thinly and not high enough to be really effective.

But if the bottom of the niche is properly sloped to drain and the waterproofing membrane is at least intact there, the hole you show behind the niche tiles should not cause you serious problems. The gap shouldn't exist at all as the area behind that tile should have been at least 95 percent filled with the tile bonding mortar. The gap is something you wish weren't there and you could have lingering moisture in there and maybe keep your stone darkened in that area or allow mold growth on any organic matter that could possibly get in there over the years, I suppose, but you've got far greater problems with your shower than that, eh?

My opinion; worth price charged.

SWB04 01-22-2015 03:26 PM

5 Attachment(s)
Quote:

Originally Posted by cx
Scott, best to keep all your project questions on one thread so folks can see what you're working on and what's been previously asked and answered.

I included a link to the first thread for context, and created a new thread since this addressed a specific technical question unrelated to the subject of the first thread. However, I will comply with the forum's standards.

Quote:

Originally Posted by cx
Best I can tell you've never determined that there is any moisture barrier behind your wallboard and that niche appears to be one of the few places with a waterproofing membrane applied, albeit a bit thinly and not high enough to be really effective.

There is a paper backing of some sort; can't be a moisture barrier. The new contractor applied two coats of Redgard, diagonally and then horizontally, to every place that travertine was installed, including the floor as a secondary barrier. The primary barrier was 1/4" (floors) or 1/2" (walls) Hardie CBU, and a quality hot mop job took care of the shower tub. The only area that didn't get CBU was the six inch strip at the top of the shower; that only has Redgard over the existing wallboard.

The Hardi backer ends about an 1.5" above the existing shower spout (if you look at the close up, you can see the horizontal line), and above that there is standard, 23 year old drywall. (I directed the new contractor to apply Redgard to the drywall, and mount the travertine over the top of it. That area is 78" above the shower tub; thought it would be adequate water control.

That's a problem now. When we raise the outlet six inches higher, it'll be mounted through the drywall. We're going to block the back of the existing CBU with a 4" x 4" square covering the existing shower spout hole, mounted from the back with polyurethane glue and a 3/4" plywood backing, and secured from the front with CBU screws. We'll tape and apply thinset over the area as with any other CBU seam. Then we'll clean additional mortar off the section where the tile was pulled, recoat the area with two coats of Redgard, and the area should be water tight. I'll caulk in around the new hole for the water outlet, though I guess the outer mounting plate should keep the water out).

I'd prefer to replace the 6" strip of drywall with Hardi CBU, but I don't want to disturb the rest of the installation. I can't get to the stud on the left (i.e. hardie + travertine already covers it) to secure the CBU. I'd have to block behind the hardie on the left and attach the CBU to a stud on the right, to secure new CBU to cover the 6" area where the shower spout will mount. I'm hoping that just applying Redgard over the CBU and wallboard will be sufficient.

Quote:

Originally Posted by cx
But if the bottom of the niche is properly sloped to drain and the waterproofing membrane is at least intact there, the hole you show behind the niche tiles should not cause you serious problems.

There are two 3/4" solid travertine shelves that the crew made from counter top remnants they had at their shop (worked out really well). The shelves are sloped, though I suspect the slope was achived via mortar bed - the niche was a square box before tiling.

Quote:

Originally Posted by cx
The gap shouldn't exist at all as the area behind that tile should have been at least 95 percent filled with the tile bonding mortar. The gap is something you wish weren't there and you could have lingering moisture in there and maybe keep your stone darkened in that area or allow mold growth on any organic matter that could possibly get in there over the years, I suppose, but you've got far greater problems with your shower than that, eh?

Honestly, what I observed during the installation likely met the 95 percent standard. The problem is that my standard is 125% filled (if I can't play in mud, get it all over everything and myself, then I'm just not happy). :-D

I guess I'll just ask them to fill the void as best they can, and put the tile back up after we prepare the wall.
a
Regarding the "you've got far greater problems with your shower than that, eh?" I think we've resolved the major issues (though I just created this one by the late change request, i.e. I'm paying them for the additional work).

This isn't a "10" on a ten point scale at all, but judging from where we started, and the work these guys picked up, I believe that they did a pretty good job.

Thanks for taking the time to respond.


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