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Quantity Of Plies In Plywood

Question: I am about to purchase some 3/4 inch plywood to build a porcelain tile countertop. I went to my local lumber yard and discovered that all plywood of a specific thickness does not have the same number of layers. Whys is this and is it better to have more or less layers?

Answer: In short, the more plies or layers of veneer, the higher the quality of the plywood. However, there are special applications when fewer plies in the plywood are desirable.

Thinner layers of plies bond or laminate better than thicker layers. Hence it is less likely that your plywood will separate between bonds if you have more bonds or layers in the same thickness of plywood. In theory the more plies that you have the flatter the piece of plywood. However after 5 plies the variation in flatness becomes meaningless.

The more plies the better the grip on screws and nails. In your case this would have little meaning as you are not screwing something to the plywood but will be screwing the plywood to the cabinet frame or box.

For your countertop I would recommend that you use exterior grade plywood. Should water penetrate the tile and its corresponding grout, less damage to your base plywood will occur with exterior grade plywood.