tile grout options

[pinya]

I live on the third story of a 5-story condo building, and our Homeowners association requires that we put a specific cork sound barrier down under any hard floors we install--

So we are having

1000 square feet of porcelain tile installed over the Acousticork R60 6mm cork which is on top of our concrete underlayment and that is all fine and good. The problem now is with the sanded grout we are using with acrylic grout additive that our installers have used many times with success. But in our case, they have grouted a small area, and after several days, it still seems to be flaking off- just not very hard like it should be. We can scratch it out fairly easily with the grout removal tool, much easier than with the grout in our bathroom which has been there for 10 years. On top of that, the installers said they test jumped on it and the grout is starting to show crack lines.

Now our installers are saying they've talked to a more experienced tile installer in town, as well as some kind of National Tile Association, and both have told them we need to put epoxy grout.

My question is, has anyone out there had to use cork underlayment under a tile installation, and what type of grout did you use? I'm a little against using epoxy grout, I don't think it should be necessary in a condo with only two people living there, and it's such a toxic chemical. I would like to find out if normal sanded grout with the acrylic should be okay, and maybe something else is causing this problem.

[m Ransley]

Maybe a bad or old batch of grout, old as in improperly stored in high humidity and the cement has already partialy cured, bad as in a factory mistake of the cement mix . Try a different new batch , from a different company, just a guess.

[tbasc]

Tile Council of America Installation Guidelines are on the internet. It occurs to me that a cleavage membrane or membrane waterproofing may be needed between the cork and the tile setting bed. This would insure that the cork does not affect the mortar set.

TB

[Michael Baugh]

Why is the cork on TOP of the concrete underlayment?

[John B]

Good question. But anythng flexible beneath tile would seem to be problematic, in my opinion.

[John B]

irrelevant, and faulty critereon for any design consideration

[m Ransley]

Does the cork company recomend tile directly over cork. Cork is not completely ridgid. I hope you are holding All of the cash owed till you know everything is correct. Any flexing under tile can cause cracks and tiles to eventualy loosen.

[pinya]

It seems that like you say, the flexing is the culprit. We did our own tests on the tile this weekend, jumping on it, and it did weaken the grout until it was crumbling. We even broke a tile just jumping very hard on it. You can even see the tile move a tiny bit when the other person is jumping on it. Whether it's the cork, our concrete underlayment, or the way it was layed I don't know.

The cork company website shows tile directly over the cork and I believe our contractors talked to them (the company Acousticork) before installation. We have already tried two different bags of the grout. A sales representative from TEC, the grout company, is coming over tomorrow to take a look; but it looks like we may have no choice but to put epoxy after all. I'll post the results when it's all said and done.

Thanks.

[m Ransley]

If you are cracking tile and it flexes NO grout will help, you will probably have to rip it up and start again as no flex should be there. Bad news but you hired a hack. Get a few Pros out the tile store and talk to the tile Co, get opinions in writing to confirm this. Photograph it Video it, and talk to a lawyer. Cork being the problem or not subfloor is NG. I dont know who is at fault, I hope the cork Co as they have deep pockets. If tiles crack now wait 5 yrs, they will be comming loose.

[pinya]

You were right. What finally happened is that we found out the tilers had done a 5-point mortar installation, meaning they put a thin layer of mortar on top of the cork, but really only had the tile cemented to the floor at the corners and the center of the tile. The Acousticork company AND the tile assocation of america both said that was NOT going to work, especially over cork. So the tilers removed everything (the upside of the bad installation was that they were able to easily remove the tiles without breaking them) and retiled it all the normal, mortar-everywhere way, as well as putting epoxy grout in which acousticork said was necessary. Aside from being out of our condo for

2 months, we're very happy with the way it turned out now.