[MustangDave]

Hello all. I’m in the process of a full rehab on my main bathroom in a 1940’s brick house in Pennsylvania. The original floor cracked because the previous owner, genius that he was, removed a support from the center joist which I have now fixed. Original floor was mud bed that I removed completely.

The construction of the old floor was something I haven’t seen before. A wood subfloor was installed between the joists about 2 ¼” below the tops of the joists. The mud bed was installed on top of the subfloor to a depth of 3”, leaving ¾” above the tops of the joists. Then the tile was installed over top. All of the plumbing was embedded in the mud bed also. Floor dimensions are 10 ft by 4 ft.

Wife wants radiant heat in the new floor, and we’re going with hydronic / pex. Drawing attached. The only change from the old floor is the pex.

- I’m gathering there needs to be a moisture barrier between the subfloor and mud bed. Planning to use 4:1 deck mud unless you suggest otherwise.

- I’ve read in other threads that reinforcing mesh should also be used. Is this recommended and would it be applied on top of the joists?

- Anything else that needs to consider here? Better ways to do this job?

I’ve done a number of small, simple floor projects, but I feel this one warrants some serious advice to get it right.

Any help is greatly appreciated!