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Minimum thickness of mud job

JOE_99 Member Posts: 15
Installing another leg of 1/2 in PEX for small bathroom (remodel). What would be the minimum thickness of mud job .Will be titling over the mud job. The sub floor is 1X4 and about 40 years old,good shape. I had taken out old mud job. Will be using tar paper and metal mesh under mud .
Plus what is best way to tie down PEX tubing to metal mesh?
What is closest point of to lay PEX next to toilet so the wax ring is not affected? I will be keeping temp around 125 degrees.


  • ratio
    ratio Member Posts: 3,178
    FWIW, I've switched over to the foam toilet rings. So far (≈2 years) no issues, three locations. I think it'd suck to have to avoid the floor right in front…
  • Paul Pollets
    Paul Pollets Member Posts: 3,509
    Tar paper is a no-no for underlayment under a radiant application. It will offgas VOC's and permeate the home with tar smells. I'd also use 3/8" pex on 6" centers. Covering should be at least 3/4" over top of tube so 11/4" min over the tubing. A fracture-proof membrane should be installed before tiling to minimize tile or grout popping.
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,689
    I agree with @Paul Pollets on everything.
    However I did use tar paper throughout my house and had no smell whatsoever.
    Fracture proof membrane is a must.
    I did 1 1/4" mud bed with 3/4" over the tubing.
    No grout/tile pops, no cracks-10 years (knocking on wood).
    I borrowed the staple gun on a stick to fasten the tubing-from my supplier, for the job.
  • hot_rod
    hot_rod Member Posts: 16,312
    I think you would need to get well above 150F for asphalt felt paper to off gas? Owens suggests at 200F it will release VOC. In a mudset I doubt you would see temperatures anywhere near that. At least if you want to stand on the tile :)

    I would staple or use conduit clips to keep the tube down to the mesh. It's not so easy to tie to that tile mesh. I think I would put the mesh over the tube for it to be of value and into the mudset.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • JOE_99
    JOE_99 Member Posts: 15
    I do agree. I unfortunately did that already once in my other bath room.
  • JOE_99
    JOE_99 Member Posts: 15
    I ended up using small plastic ties, about 4 in long. Used two on turns and one in straight a ways. Now they only have to hold until the mud dries. I did not want to use clips (had thought of that) and put all those holes in the floor boards.