Several months ago we installed ceramic flooring in the entire house over the existing cement floor. A couple of months later we noticed that the grout in the guest bathroom was beginning to look like someone sprayed flour over it. Not all of it, but randomly spread over about 20% of the grout lines. At first we thought it was Sheetrock powder from drilling holes in the walls to install various fixtures, but since vacuuming and mopping did not remove the white stuff (embedded in grout, we realized) we decided to scrape it off. Needless to say, after a couple of weeks it all came back. After removing the wall from the other side of the bathroom (living room side), we found a leak coming from a pipe. We fixed the leak and have been drying the beams for about 2 weeks now. However, how do we dry the thin-set under the tiles which is obviously wet? Right now some of the grout is nice and gray (dry, unaffected), some is almost black (obviously wet) and some is covered with white powdery substance. HELP please.
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If premixed grout or thinset was used you’ll probably need to re install the effected areas. If you used standard dry bagged type thinset mortar and grout you’ll probably be alright. The bagged mortar and grout can be submerged under water. The dark is probably just moisture and will go away when it dries. The white spots are probably a bit efflorescence (salts rising out grout).
Use a fan or dehumidifier to dry it all out. If you had a leak for awhile the concrete below is probably saturated and will take awhile to dry out (possibly weeks). Once you’re confident it’s all dry and hopefully dark spots are gone you can tackle the efflorescence. Can use a grout haze cleaner for that. If that doesn’t seem to cut it go into a heavier duty acid type cleaner (follow safety instructions carefully). You can find these cleaners in all the big box stores and tile shops. If the grout was sealed that can lead to trapping moisture from below and will keep cleaners from removing efflorescence, so you may have to manually remove that. That’s all I got. Hopefully it all works out for you.
Thank you, jlyda. You gave me some hope. The thinset mortar and the grout both came dry from bags, so, maybe in time they'll dry out. I put the fan in the bathroom now and that will speed up the process. Now we just have to be patient.
I am so grateful for your input.