Pebble floor and Flexcolor CQ

[Steve72]

Hi, I'm a homeowner who recently had a shower redone. Tile guy wanted to use Flexcolor CQ on the whole job. After the job was completed, I noticed that mapei said not to use on mosaic pebble tile sheets with larger than 1/2in grout areas. There are several spots in the floor of the shower with larger spaces. After waiting a week, I noticed some shrinking and cracking in the larger spaces. He returned and grouted over those areas, filling them in. I waited another 6 days and everything looks better. Just wondering if this will hold up ok and I won't have any issues with water penetration.

[ss3964spd]

Hi Steve, and welcome. We've moved your post out of that other long thread since that one is more like a "what's your experience with..." type of thread.

As to whether the CQ will hold up or not, hard to tell, the only things we really know is that the grout has been installed in a manner inconsistent with the manufacturers directions, and that your installer ought to have read those directions. I would definitely check with the manufacturer to find out if going over previously installed CQ with more CQ is acceptable.

As for water tightness, the tile, well pebbles in your case, are not meant to be water proof; the construction of the shower receptor under the pebbles and grout is what must be water proof.

Do you know how the receptor was built, what water proofing system was employed?

[speed51133]

Not much you can do at this point, but yes you are correct. You are not supposed to use it with joints that big. I believe the biggest concern is that it will crack and shrink as you experienced. It doesn't become rock hard like cement grout.

[cx]

Welcome, Steve.

I'll see can I get one of our MAPEI reps to have a look at your thread and comment.

The answer to Dan's question above about how your shower receptor was constructed will be telling in whether a successful replacement of that shower floor will be possible, but in any case the successful correction of the situation is clearly your tile contractor's responsibility.

My opinion; worth price charged.

[MAPEI - Technical Service]

Steve,

As others have mentioned above it’s hard to say what might happen at this point. If the first installation started cracking and shrinking, you may see the same out of the second layer.

Besides the cracking and shrinking, we advise not applying Flexcolor CQ in joints wider and/or deeper than 1/2” because it may not dry properly, or only dry on the surface and stay wet in the middle of the joint for an extended period of time. This can lead to soft joints, and with more use of the shower you may see areas start to soften and wash out of the joints.

At this point, you can either wait and see if it’s going to give you trouble, or have a chat with the installer about what it would take to remove and replace the installation to remove all doubts.

I hope this helps!

[Steve72]

Thanks for the replies. The pebble mosaic Stones were sealed prior to installation and grout work. The shower pan is built from a layer of mud mortar bed, shower pan liner and then another layer of mud or bed mix. The pan floor was painted with aqua defense but not the whole pan only the outer areas leaving about a 12-in space around the drain area. After spending all the money and hassle on getting this shower done, I'm just paranoid about it failing. What I think is, the installer liked using this grout because it's easy to work with for him and it doesn't have such a quick curing/drying time. I feel like we should have used the ultra colorplus FA. This is what I actually had until he recommended the other and I exchanged it.

[cx]

Well, the good news is that you can easily (easily for your contractor) and relatively safely just replace that floor, which is what I'd recommend you have him do. And that would be entirely at his expense.

And invite him to please not put any kind of direct bonded waterproof membrane over the top mud bed this time. That is not an improvement over the traditional shower receptor he built. It can, in fact, cause problems with that receptor that you neither need nor want. If he did a competent job of creating the traditional receptor, it should work fine until your grandkids come home from college.

My opinion; worth price charged.

[Davy]

If he installed two mud beds then it sounds like he did put a preslope mud bed under the liner, which is a good thing. Someone still needs to explain to me why adding a paint on membrane to the top of a mud bed that already has a liner under it is best. If the pan liner is installed correctly, it won't leak. Adding Aqua Defense may or may not cause problems but I don't see it preventing any.

The installer needs to learn the limitations of the products he's using. Makes me wonder how the curb was done.

Cx is pretty fast today.

[Metropolitan Ceramics]

I know Holden from MAPEI gave you the straight answer but I'll fill in some color since I was working at MAPEI while CQ was being developed. The reason we didn't recommend it for pebbles at the time was because there are often dips in the larger grout joints between the pebbles that hold water. Over time, water sitting in the low spots can soften the grout especially when first installed. If you don't have dips in the grout in the larger grout joints and you allowed it the full seven days to cure before first use, I wouldn't anticipate it being an issue long term.

[cx]

Thanks, Dan. That's the kind of information that I find really helpful for our visitors.

Although I don't know just how a fella would grout one of those "pebble" floors without any dips. And that sounds like it could be the problem with some or all the tile shower floors we've had reported when using those grouts. With insufficiently filled joints and insufficient slope provided by some of the foam trays included in some of the shower waterproofing kits, I can see places in the grout joints remaining wet for extended periods.

My opinion; worth price charged.

[Metropolitan Ceramics]

CX, a few years ago I lobbied the Handbook committee to implement a steeper slope for pebble and irregularly shaped shower floors (1/2" in 12 instead of 1/4") but it didn't gain a lot of traction. Most of the issues with pebbles are due to poor drainage. It can bring latex and efflorescence to the surface of grouts, make the grout look 'wet', especially around the drain, and lead to mildew and staining. I would still recommend to anyone working with rounded pebbles to use a steeper pitch that you would for typical flat tile or stone.

[cx]

Haven't been to one of those meetings for years, Dan, and I'm sorry I missed that one. I coulda at least stood up in the back of the room and hollered, "Hear, Hear!"

Seems it would be fairly simple to at least add a comment in the Natural Stone Tile Selection and Installation Guide portion of the handbook.