View Full Version : Tile subfloor

11-23-2008, 06:28 PM
The floor construction in our home consists of a 7/8 thick subfloor,
7/8 thick hardwood floor, 1/4 plywood sheeting which makes the floor pretty thick.
Can I lay the Hardiebacker board on top of all this, So I can lay a tile floor?

11-23-2008, 06:49 PM
If you have all of that wood sub-flooring, why would you want to even bother with backerboard?

11-23-2008, 07:08 PM
No. Not because of a strength issue, but because dimmensional lumber just moves too much from season to season. 1/4" ply is often luan, which is quite unstabile just the moisture form thinset can cause it to delaminate.

Is the first layer wood planks? Those can stay, but you need at least 1/2" c-faced or better ply on top of the planks to isolate you from the wood. The ply needs exposure I glue (not to glue the ply to the subfloor, to make the ply).

Then, you need some sort of isolation membrane or cbu, installed properly (thinset under then screws or nails), then you can tile.

If you want a long-lasting tile install, you also need to verify that the joists are okay.

The floor you have is plenty stiff between the joists (but would move too much in the seasons)...now you need to determine the strength of the joists.

Check out www.johnbridge.com (http://www.johnbridge.com) for tiling info.

11-24-2008, 06:00 AM
Good idea to check john bridge forum. Actually, I am thinking that you are OK. There is the question mark about the movement of that hardwood, but I would be inclined to use RedGard, or the Schluter membrane system, on top of your plywood. See what they recommend over on johnbridge.com

11-24-2008, 06:15 AM
1/4" ply just isn't stable enough for tile and won't isolate movement from the hardwood underneath. Industry standards call for a minimum of 1/2" ply above dimmensional softwoods (which don't move as much as hardwoods with the seasonal humidity changes). Plus, there's almost no 1/4" ply that has the right glue - luan certainly doesn't.

Plus, getting screws or even nails into hardwoods to hold down the cbu would be a major pain.

11-25-2008, 04:12 PM
Thanks for the info everyone, I think I may go with something else instead of tile.
I just can't remove the 1/4 plywood without changing allot of other things
Thanks for keeping me from making a big mistake ans having a bad tile job.