We are having a discussion in our house about the right way to tile the kitchen countertop. I am using a 6.5 inch porcelain tile and am using the more expensive premixed base to eliminate any uncontrollable factors (i.e. my mixing) and floor grout as recommended by the supplier. Instead of putting down new external plywood, can we instead put a sealant on the plywood and pressboard base that is already there and patch where the pressboard meets the plywood and then apply the tile. I am concerned about this approach as in all my readings I do not see any suggestion of it and I want to do the job right. I am concerned about bonding.
Answer:
The ideal situation would be to get rid of plywood and particleboard and lay in new of either kind - not a mixture of the two. You could also just lay 1/4" poplar or mahogany plywood on top of what is there and go ahead with the tile. You are presently dealing with two sub-structure products that will re-act in different ways to adhesive, atmospheric humidity content, and stress. I 'm not in love with that idea. Remember, if you have a problem, only some of the expensive tiles will be re-cyclable, not all.
