106 year old house – on top of the joists (16" on center) are wide 3/4" thick boards at a 45 degree angle, then 3/5 tongue and groove on top of that. Putting 3" marble hex down and plan to use a 1/2" thick Ditra-Heat uncoupling membrane.
Is that enough support under the tile or do I need to add hardibacker or plywood too? I am trying to minimize height, it's already above the wood floor in the hallway.
Thanks!!
Best Answer
if you install over wood, you will eventually have cracked tiles and/or grout. it is not a stable substrate.
If height is an issue, I would take out the tongue and groove flooring, and install the cement board on top on the 3/4" subfloor.
For floor, i use 1/2" cement board.