about 8 tiles out of 100 have come back up? Is this due to incorrect sub-floor? We have old home with close to 5 inches of subfloor already so we thought we just needed a solid base for tiles but are afraid all are going to come up now???
Appreciate any advise that might save this job!
12X16 area done and 9X16 left to go?

Hi
I guess what you mean is exterior grade plywood?..or do you mean chip board?....anyway, tell us what you used for adhesive, and how long you stayed off it while the adhesive was drying.