With 1/2 of my new subfloor down in my bath remodel I just read this morning on a tile forum elsewhere on the internet that CDX plywood is just plain bad for subfloor under tile (or subfloor at all) due to the possible voids. Also, it suggested that CDX really isn't exterior grade. I thought that's what the "X" means. Is that not correct?

Just wanted to check the consensus on here and see if any of you have used it under tile successfully. I consulted with a friend who has done much building in his life, and he suggested the CDX plywood.

I'm at the point that I could take out what I have put down, though I really don't want to. But neither do I want to have failing tile in a short amount of time. If I do have to remove the CDX, glued and screwed down, how hard is it going to be to get the wood up due to the glue? Any tips or tricks?

 

You don't mount tile directly to wood, anyway. You will be installing 1/4" hardie backer or durock on the subflooring, so the voids become moot. Imbed the backer (cbu) in thinset and screw it or nail it down as per manufacturer's recommendations and then lay your tile on that.

 

Thanks for the input. My own mistake, though, in that when I rechecked the material I purchased for my subfloor I found that it IS NOT CDX. I had bought BC Exterior plywood, so all is well. That's the grade that the tile forum folks and then a local tile store was suggesting. So, no ripping out, and I can move ahead.