Cement board underlayment on 1×8 subflr
Any thoughts on installing 1/2″ cementboard underlayment on existing 1×8 diagonal floor sheathing? We plan to glue and screw the material right over the sheathing after refastening the sheathing with screws. The sheathing is gapped anywhere from 1/4″ to 3/4″ on 2×10’s at 16″ o.c. Ceramic tile (1/4″) will be installed on the cement board in a standard setting bed. Anyone out there had any negative experience doing this. I don’t have any reservation but want to assure the homeowner.
Also, we have had some discussion in the office regarding the pros and cons of using hardibacker/durock vs. Wonderboard. Anyone care to weigh in?
In my experience this is a marginal installation, although some guys have no problems. Tile council rec's 1 1/4 inch structural. Backer board is not structural. What about a mud bed? If you don't have the height, I would go with 1/2 inch underlay grade plywood, then your backer.
My two cents. 1/4 inch floor tile? Are you sure they are floor rated. I have never seen ceramic 1/4" tile for a floor. I would go 1/2 plywood, 1/4 or 3/8 inch backerboard and 1/2 inch tile. use wood or marble transition. This will hold up fine.
Edited 2/21/2008 2:46 pm ET by kbd
I was wondering about that thickness myself. Maybe a sheet mosaic pattern- sometimes is a quarter inch
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My bad it is 1/2" x 12 x 12, and we are underlaying the cement board. Thanks for the help.
I forgot about those, the ones attached to the mesh are about a 1/4 inch. I was worried he was using the wall 4x4s on the floor.
I would be planning to glue and screw some plywood underlayment first, then the cement board
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Add 1/2" plywood and use Ditra under the tile. I would use Ditra regardless but for your case, you'll also benefit from the 1/8" thickness of the Ditra. Cement board is a poor choice in any situation, Ditra and some of the other products protect against cracking, are MUCH easier to install, cost the same and can be used with kerdi to get a completely waterproof floor.
"Dry pack" it.
Bob's next test date: 12/10/07