July 8, 2013
I'm sure it will. I used it over thinset covered surface since it was now pourous. I had installed Kerdi material over the drywall with thinset per their instructions but ended up having to remove it all, which left the thinset. Rather than removing the drywall and putting up cement board, I elected to use the RedGuard over it. Two coats of this Redguard in two directions, thinset and tile over that seemed to work just fine, for me.
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