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securing pex tubing to sub floor

Warmfoot Member Posts: 127
When we do hanging systems without plates, we use the sioux chief touchdown clamps. We have found that they make the least amount of noise when reaching higher water temperatures. Then we also control the system using constant circulation to also minimize the noise. my two cents

Ernie Bogue

Master Hydronics LLC


  • Joe Baron
    Joe Baron Member Posts: 1
    securing pex tubing to sub floor

    Ok folks I need some help. My question is this, what is the best way to secure pex. The tubing is being installed under the subfloor, in between the joists. Aluminum plates and gybcrete are out of the question because of cost. Are electrical one hole straps a good way to go? 1/2 inch electrical straps seem to fit a little loose over 1/2 inch pex. Is it better to have the tubing hang slightly below the subfloor? I know they sell those plastic straps that snap around the tubing but there expensive. What is a good way to secure the pex that doesn't cost alot.
  • kframe
    kframe Member Posts: 66


    For this kind of application, you really should use the aluminum plates, especially if you're putting under a floor finished either with carpet or strip flooring. Yes, the plates are expensive, but they add significantly to the efficiency of the system.

    Perhaps you could make your own with roll flashing and a brake; I don't know.

    Quite frankly, though, I'd advise installing the system as recommended, or simply NOT installing it at all.

    I really do not think that there's very much sense or logic in going to the expense and effort of installing this kind of heating only to cheap out and very possibly compromise both your efficiency and satisfaction by cutting corners.

    As for positioning, I'm of the opinion that in an under floor joist pocket application the tubing should be, as much as possible, in direct contact with the underlayment above it.
  • Tom Meyer
    Tom Meyer Member Posts: 300
    RPA guidelines for tube in Wood Joist Space

    The Radiant Panel Association Guidelines is available at:


    "16.3 Wood Joist Space

    a. Tube should be attached to the underside of the wood subfloor or the floor joists with staples or fasteners which are compatible with the tube material and do not damage, nick or chafe the tube.

    b. Floor joists may be drilled to accommodate tubing. Such drilling should be as close to the center of the joist as possible and is permitted by local codes.

    c. Formed metal plates may be used to support the tube and to assist in the lateral and conductive heat transfer to the wood subfloor. When metal plates are used, a minimum of 1/8" should be maintained between the butt ends of the plates.

    d. Batt (insulation) may be placed horizontally beneath the tube in a manner specified by tubing manufacturers design criteria.

    e. Care should be taken to insure a minimum of air infiltration into the joist space from rim joists, plumbing and electrical penetrations or other sources of outside air."

    Senior Designer/Trainer
    Precision Hydronics Corporation
  • hot_rod
    hot_rod Member Posts: 21,857
    Check your loads first

    To make sure a staple up or suspended tube application will meet the load without overheating the subfloor and final floor surface.

    I agree transfer plates are the best way to fasten pex to the bottom of the subfloor. I'm not sure stapleing pex with a metal clip or wire staple is a good idea. Too much potential for movement and wear as it heats and expands.

    Suspended tube with the appropiate clips or brackets is an option if the loads warrant it.

    If it's worth doing, it's worth doing right :)

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
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