I had to cut a few access holes in the new subfloor in my new attic bath to make a few changes. I will be using 12 x 12" porcelain tiles on the floor. My contractor suggests that I need to add a second layer of 1/2" plywood screwed in over the first, then a layer of cement board or other moisture barrier.
He says that because the tile is larger sized, it will tend to come loose unless I make the floor more rigid with a second layer of plywood.
Anyone heard of this? It will be a real challenge for me to get it done for a variety of reasons. Also, I have a double sink and I stacked two san tees to make the arms. I calculated the distance from the floor carefully and it could change things.
Does this really need to happen to keep my tiles from coming loose? I've never heard of it before.