A deck above living space was repaired last summer after discovering water damage below. After installing a waterproof pvc membrane manufactured by Duradeck, porcelain tiles were set. I recently noticed several locations where water is seeping up through the grout joints. Water must be penetrating through the grout on rainy days and after the sun has warmed the tiles the water will evaporate, leaving a stickiness and an efflorescence on some of the tiles and grout joints!

The thinset and grout used are latex based, so wondering if the white substance is actually due to "latex migration" instead of efflorescence. In any case, I have only tried to clean by scrubbing with concentrated Simple Green using a 1 to 5 dilution. Although I was able to eliminate the stickiness on the tiles after scrubbing, it did not remove the white substance. It's like it's baked onto the porcelain and I've only been able to scratch some of it off the tiles using a sharp putty knife! I purchased some sulfamic acid crystals, but not sure if this will solve the white residue issue if it's "latex leaching" vs efflorescence!

The grout joints are only 1/16" wide so I'm wondering if the water is seeping through because I didn't get enough grout in all of the joints. I sealed the grout joints last summer using Miracle 511 Impregnator Sealer. Is there a more effective sealer that I should be using? If I do nothing, is there a chance that the thinset could become compromised? I'm not concerned about any water damage into living space areas below the deck as the pvc waterproof membrane should be adequate.

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  • You applied a membrane because tile joints are not waterproof. Why are you expecting them to be? Also, grout sealer protects color against dirt and stains. It isn't intended to seal the joints in the way you're thinking. – isherwood Apr 13 '18 at 20:33
  • My concern is the amount of water that's being drawn up through the grout joints when the tiles heat up during the the day. Yes, I realize that some moisture tends to penetrate through the grout when it becomes wet, however, I've never encountered "puddles" such as described above! Will the thinset eventually deteriorate over time causing tiles to loosen as a result of this water penetration? Also frustrated with the efflorescence or "latex leaching" after the water drawn back to the surface has evaporated. Is best solution to regrout areas in close proximity to where these puddles occur? – Grant Apr 14 '18 at 16:34

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