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Installing PEX on wood subfloor. Pondering potential layering of / durock / pex / masonite?

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slw4223
slw4223 Member Posts: 3
in Radiant Heating

Installing PEX on a wood subfloor, planning to use 3/4 plywood with tracks cut in and reflective plates. (floor trusses will not support the weight of a poured cementious layer)

  • Would there be a benefit of installing 1/2' Durock on top of the 3/4 plywood with pex? (creating a slight monolithic slab?)
  • Finished floor will be LVP, so thinking to install 1/4" Masonite before the LVP

Thank you!

Comments

  • hot_rod
    hot_rod Member Posts: 26,604

    The Durarock would add a slight amount of thermal mass, but also some weight and small thermal lag, more r value to drive through

    I would use an underlayment ply like Revolution Ply, Lowe’s sells it, instead of Masonite, in case it ever gets wet

    Or the finish floor over the ply and tracks.

    See what the flooring manufacturer recommends for under layment

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    bjohnhy
  • slw4223
    slw4223 Member Posts: 3
    https://forum.heatinghelp.com/discussion/comment/1878726#Comment_1878726

    Thank you, will look at the Revolution Ply!

    Thoughts on placing Durock under the PEX vs on top? I had originally allowed 1 1/2" for gypcrete. We can carry an additional 7lbs per sq ft on the floor trusses, so the weight and thickness of the Durock is ok.

  • hot_rod
    hot_rod Member Posts: 26,604

    is the flooring a floating, glue down or nail down?

    Generally those cement board products use a special coated drill point screw to fasten in or through them.

    I doubt a hardwood nail gun would like the Durock?

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    bjohnhy
  • slw4223
    slw4223 Member Posts: 3
    https://forum.heatinghelp.com/discussion/comment/1878742#Comment_1878742

    Floating floor LVP

  • DCContrarian
    DCContrarian Member Posts: 1,369
    https://forum.heatinghelp.com/discussion/comment/1878752#Comment_1878752

    Make sure the manufacturer approves it for this application. Vinyl expands quite a bit when heated which can cause it to buckle. I know some LVPs are not approved for unheated spaces because they will shrink so much when cooled that the joints will come apart.

    bjohnhy
  • bjohnhy
    bjohnhy Member Posts: 144
    edited December 24

    I don't think you'll gain much with a layer of dura rock. Especially if the reflective plates are aluminum or such, to help distribute the heat.

    It'll give youMore thermal mass, could be good or bad. But it'll also impede heat flow, (add r value) requiring higher supply temps for same BTU output.

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