I will be installing porcelain tiles in a small bath and want to use 3/4" exterior plywood over the subfloor. I will covering that with Ditra matting. I went to Home Depot and the only 23/32" I could find was "Certified sanded". It looked real nice on the sanded side but it was not tonque and groove (don't know if that matters) and it didn't say exterior or exposure 1 etc on it. Anyone familiar with this stuff?

Thanks,
Jim

That plywood your looking at is cabinet grade plywood. If you want exterior grade you can use OSB tongue and groove (this stuff has come a long way regarding durability) or pressure treated plywood.

I wouldn't spend the money on sanded plywood to use as a subfloor under Ditra.

Thanks for the reply. I ended up finding some 3/4" t&g exterior grade plywood.

Jim

I will be installing porcelain tiles in a small bath and want to use 3/4" exterior plywood over the subfloor. I will covering that with Ditra matting. I went to Home Depot and the only 23/32" I could find was "Certified sanded". It looked real nice on the sanded side but it was not tonque and groove (don't know if that matters) and it didn't say exterior or exposure 1 etc on it. Anyone familiar with this stuff?

Thanks,
Jim
If your lying ceramic tile your supposed to leave 1/8" expansion joints in between each sheet, T&G was used for several years back in the 70's and after a few years what would happen is the plywood expanded and contracted against each other and cracked the floor.
You also should be using a full flex thin set for plywood, your plywood should be glued with PL-400 or similar and screwed down using allot of screws.
Good luck