On Dec 17, 11:24*am, "Pete C." wrote:
RBnDFW wrote:

I am finishing a bathroom counter.
It's approx 75"x25" and will have two sink bowls

Right now I have the top made from 3/4" plywood. It is not marine grade
plywood BTW. The tiles are cut and ready to lay.
* * My original plan was to use structural adhesive to attach the tiles
to the plywood and then grout.
* * But I bet I need a waterproof substrate - backer board, cement
board, Hardiboard? * Problem is I don't want to make the top any thicker
than it already is, though 1/8" or so would be fine.
* * Any suggestions welcome on materials and method. *I only want to do
this once.

A layer of cement tile backer board would be appropriate, the same as
tiling a wall. I would however suggest you reconsider the idea of tiling
the counter as in my experience tiled counters are less than ideal. Tile
counters are hard, noisy, the surface is not level so bottles rock, and
the grout lines are a royal pain to clean.

For years tile has been installed on kitchen counters long before the
invention of cement backer board. My friend did his counter top in
tiles that are the same width as the counter top and grout lines are
very thin. Black tiles with very dark green grout is epoxy type, needs
no sealer and no problem to clean.

Jimmie