I have a small bar area at my house where I recently decided to put granite tiles on the counter. Theorizing that since it was a counter and not a floor, I did not use Hardibacker or a similar product. The counter surface I adhered the tiles to was a solid wood at 3/4 of an inch (but a better grade than plywood). The guy at the big box store suggested I use a pre-mix product made for stone. It resembled the kind of adhesive you would use for vinyl flooring or outdoor carpet. I got the tiles on there nice and level, let it set for 48 hours, then grouted. About a week later cracks began to appear in the grout lines and the tiles appear to have "heaved." Any ideas what went wrong or if it can be fixed? The counter is 17 inches wide and I put 12 inch tiles on it.
Looks like your wood absorbed moisture from the thinset and swelled up. I did some tile research recently, and not a single place recommended gluing tiles to wood. They all say use at least a 1/4" backer, mortared, screwed, taped and patched.