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heating an existing slab of concrete 6\" thick.

Fred S.
Fred S. Member Posts: 1
We are currently working at a job site where a customer has a 6" thick concrete slab in an entry way. The slab is suspended over the cellar stairs with access underneath. We are looking for ideas to heat the slab with some form of radiant. The slab is aprox. 72 sq ft. The biggest problem is tryng to fasten tubing to the slab. Any ideas?


  • GMcD
    GMcD Member Posts: 477
    Consider capillary tubes in a thin-set topping

    Check the capillary tubes at www.naturalcooling.com You could install them on top of the slab, in a thin mortar bed and tile over it if you are considering a hydronic heating system connection.

    Or you could use 1/2" PEX and use a thicker layer of lightweight concrete topping on top of the existing slab- about 1-1/2" cover should be OK. Probably have to bush-hammer the existing slab surface to get some "bite" for any topping layer.

    Or use electric film type radiant heating elements under a layer of flooring on top of the slab.

  • hr
    hr Member Posts: 6,106
    Are you trying

    to heat from below? Or can you fasten tube to the top and add a new floor covering layer? Is the space below heated?

    From below will be a tough go. It will take a while to get that thick of a slab up to temperature. The link below has some data.


    Also fastening below will not be a good as a connection as with tube encased in the concrete pour. If you do go underneath consider some heat transfer plates for better thermal connection.

    Yet another top option would be an electric mat or cable, for that small or an area it would be a good match. Many of these install in a thinset mix and have tile directly on the cable or mesh. This would put the heat very close to the final covering.

    Tube on top could be installed with condiut clips and concrete nails or tapcons. Use a pex rail strip, or I have even glued PAP to concrete with liquid nail. Check with the manufacture of the tube before using petro based adhesives on the tube, however.

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