A theoretical question … maybe it’s too obvious.
Assuming the floor is sound, no deflection, etc … why go to the expense of using Ditra or even Hardie. Why not just staple down a layer of roofing felt and lay the tile on top of that?
I’m sorry, I thought you wanted it done the right way.
A high-performance single-family home builder shares tips from his early experience with two apartment buildings.
Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.
Start Free Trial NowGet instant access to the latest developments in green building, research, and reports from the field.
Start Free Trial Now
Replies
Well, let's define 'no deflection'. Because there's really no such thing unless maybe you're slab-on-grade.
Your wood floor frame will move, both under dead load as it sags and live load as it flexes. Your tile really does not want to flex.
Hardi is great as a bonding surface for tile and thinset, and the bond there is a lot stronger than the bond under the Hardi, even if you use thinset down there which you are supposed to. The floor can move a bit and the Hardi/tile will stay fairly rigid. As far as I'm concerned the grout joints and the tiles themselves will last a lot longer with the CBU underneath them.
I usually avoid it, but I recently tore out a tile bath. There was tile over CBU, tile over sheetrock, and tile over plywood subfloor. The physical differences in tearing those three assemblies out was quite illuminating, and the CBU areas were the hardest. A crowbar behind the CBU had to move quite a bit before the tile popped. A crowbar behind the sheetrock popped tile immediately. The tile on the plywood came off in whole pieces.
An anti-fracture membrane under the CBU could only improve this.
I meant that the deflection was within industry standards.
Why wouldn't the tar paper act as a slip sheet?
I'm sorry, I thought you wanted it done the right way.
The floor will flex and move. That's a given. So the idea is to limit the flexing and that comes with more mass in the floor in relationship to your mass.
Secondly, the T.C.A recommends 1 - 1 1/4" of floor before setting tile. I prefer 3/4" plywood subfloor and 1/2" Hardibacker over it. I know they say 1/4" for floors, but it's only $1 more a sheet for twice the thickness.
This also helps with my teaching all to try to get all their floors to be 1 1/2" thick. Think 3/4" wood over 3/4" plywood. This way there are no transitions to trip over. If your whole house was 1 1/2" it would make installs soooo much easier.