Problems waterproofing a custom tile tub [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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08-05-2004, 10:54 AM
Greetings, all. A problem has come up trying to waterproof a custom tile tub/shower with steam feature. Working with more than one installer, we may have stumbled into a problem with "too many cooks in the broth."

One of the experienced tile installers insisted on a standard pan liner, installed first, prior to a Pro Red membrane. Preslope first, then pan liner clamped to a roman tub drain with weepholes, then the floor was mudded in over the liner, sloping to the drain, then CBU on the walls, benches, and curb. Pro Red over that.

The problem emerging now, seems to me, is that any water which makes it through the tile and mortar will hit the membrane, work its way down to the floor of the tub, but never find weepholes. Then what?

It's the pan liner below which is clamped to the drain, not the waterproof membrane above. I'm afraid the membrane is defeating the design of the drain's weepholes, and combining these two system was not a great idea.

If I'm right to be concerned, what's the best way to cure this problem prior to tiling? If we simply cut the membrane back on the floor, perhaps around the drain, or perhaps exposing the entire floor in the well of the tub/shower, I presume there's a likelihood that water, when the tub is filled, would work it way UNDER the membrane. We could, I suppose, chip out the concrete around the drain, making a circle around the drain, and use the Pro Red to waterproof right down to the drain where the weepholes are accessible, using fiberglas mat or mesh as outlined in the directions from C-Cure, the Pro Red manufacturer. Then we mud back in. Doesn't sound like fun. Is there a simpler fix? Perhaps the problem isn't as serious as it seems to me.

Your prompt replies would be much appreciated.


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John Bridge
08-05-2004, 07:26 PM
Hi DH,

I think the problem is supper serious, and I don't think the tub will hold water. If your PVC liner went all the way up to the top of the tub you'd be okay, but I imagine it stops just like it would for a shower. So when you fill the tub the water level will be above the top of the liner.

Using Pro Red on the surface would have been fine if there had been a way to make a positive connection to the drain with it, but there isn't. I'm afraid water will eventually work its way under the Pro Red. Ultimately it could rise above the PVC liner underneath.

Don't like the setup. Hope we get some more opinions.

08-05-2004, 09:09 PM
Hi, John. Thanks for the prompt reply. I also look forward to hearing more input from the "usual suspects."

In fact, the tub liner was installed to go to the top, well above the water line, but unfortunately, as is often the case as noted in your fine forum, CBU was installed inside the liner, and more than a few screws were used to secure the durock, plus additional screw holes near the screws where the installer found no purchase. Initially, it seemed like the Pro Red would simply cover (and solve) the problem of the punctured liner, but now, I agree with your premise, that the water might well get behind or under the liner, and rather than rising above a low liner, would find the screw holes and leak, as has been described elsewhere in the forum. Certainly, it now appears that if we were to simply cut back the Pro Red membrane on the floor, water would seep through the next substrate, hit the original pan liner, to be sure, but could also work its way under the Pro Red -- particularly when the tub was filled with water to a 13-14" waterline -- well above the screw holes in the durock and liner behind -- and leak.

After consulting with two of the top plumbers in our area, we're working on a cure where we're thinking of removing a good sized section of the floor of the well in the tub above the pan liner, including chipping out the drain, and then reapplying the Pro Red in this new well, thus bypassing the original PVC liner, which we'd remove in the well, as it doesn't seem to be helping much.

In this way, the Pro Red membrane would connect with the existing Pro Red waterproofing on the walls, benches, etc., which was well applied, and this time, correctly clamping to the drain with fiberglas mesh as outlined in the directions from the trowelable membrane manufacturer.

We're determined to do this thing right! If there's a simpler cure than this one, we'd love to hear it. (Work will begin again on Monday.) Or, if this is our best shot, suggestions from other forum participants to ensure the best outcome would be most welcome.

We feel lucky to have caught the problem prior to tile installation, after reading some of the postings describing tearouts.

Live and learn, and learn, and learn...

Thanks, all...

08-07-2004, 08:23 PM
Another question occurs to us. The waterproof membrane has been installed on the CBU on the ceiling, especially as this installation is a tub, shower, and steam shower. Will thinset for tile adhere properly to the membrane on the ceiling? Is there anything more or different which needs to be done to ensure that the tile will stay on the ceiling where it belongs? In this case, we're using tumbled travertine, in red or rust, which the client had her heart set on. (Naturally, we've since noted the opinions and suggestions here in the tile forum concerning the use of this material, particularly in showers.)

Do any of you use any kind of special anchors into the ceiling above to ensure that your tiled ceilings stay put, despite gravity?


John Bridge
08-07-2004, 08:51 PM
Hi DH,

If sounds like your fix will work if done very carefully. Like everything else in a tile shower, you only get one shot at it. :)

Thin set sticks to the membrane just fine, except the membrane will prevent the thin set from taking up quickly. I would make sure each piece of stone gets complete coverage, and that it's shoved all the way up. Don't leave a lot of thin set under the pieces. The suction should hold them up. The only time you have problems on a ceiling is when you have large pieces and they have to be leveled up which means you have gobs of thin set under some of the pieces. If you do this you have to support the pieces until they set. :)