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subfloor and additional concrete topping over existing hydronic system

I am wondering about how to best add on to the crumply concrete topping over an existing hydronic system. The area used to have tile, that needed to be removed. I intend to install 2.5mm linoleum in that area and have a level difference to adjacent flooring of 1.25" above the smooth portions of my floor.

I am intending to take out some of the concrete topping to install wood sleepers screwed into the subfloor under the radiant heat layer on the edges of the new subfloor panels, add an acrylic bonding agent to the rough concrete surface, pour additional concrete topping over wire mesh in each sleeper field. Then add 1/2" subfloor panels, screwed down on edges, glued in between and install linoleum on sufficiently dried substrate. Does this work in principal?

Could I install a backerboard instead of plywood as subfloor for the linoleum to increase the heat transfer rate? Any experiences with getting the edges to be smooth enough? Would appreciate your thoughts on this.


  • Zman
    Zman Member Posts: 7,433
    How big an area?

    This sounds messy! I pulled apart a similar system this year. The owner had made a sandwich of the different material you are describing and hindered the system's performance.

    In a perfect world you would remove the old concrete, space the tubing off the subfloor and repour the whole thing. You could  just pour a self leveling topping coat over the whole thing.

    I would stay away from your approach of sandwiching different materials. You are going to greatly reduce your heat transfer.

    What is your tubing spaced at? What kind of heat loss does the room have? What are your water temps? Do you know how much insulation is under the slab?

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • SWEI
    SWEI Member Posts: 7,356
    Where is the tubing?

    How far down in the slab, and is there insulation underneath the slab?

    Any air gap between the tubing and the flooring will decrease performance, requiring higher water temps which will increase the risk of warping or cupping.
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