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Contractor wants to pour a slab.........

........but doesn't know yet if the finished floor will be: 1) bare concrete, or 2) hardwood.

How do you install the tubing, i.e. spacing. And then if they want to go with hardwood, how do you construct the floor? Two layers of 3/4" plywood with hardwood on top?
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

Two btu per sq ft for degree difference for a slab

Comments

  • hot_rod
    hot_rod Member Posts: 21,840
    In only did one slab with two layers of plywood, it was a PITA. The plywood needed to be glued and screwed, and it really put the brakes on the heat transfer. I also tried sleepers in pours with not much success. I think the floating engineered, or glue the engineered wood directly to the slab is the best way.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Zman
  • Gordy
    Gordy Member Posts: 9,546
    I would cover your but on tube spacing.
    ZmanSWEI
  • Danny Scully
    Danny Scully Member Posts: 1,415
    edited December 2015
    I wouldn't do anything until you know what the floor coverings will be. Don't do it.
  • bmwpowere36m3
    bmwpowere36m3 Member Posts: 512
    Or just assume worst case scenario, carpet and pad.... and size accordingly.
  • Gordy
    Gordy Member Posts: 9,546
    The scenario is quite a difference between bare concrete, and a solid hardwood floor assembly over concrete. The later could end up all most an r 3 depending on the assembly.

    There is extra cost to the owner in planning for worst case with extra tube density, and higher awt that may not be needed. But if no answer can be arrived at then no other alternative but to plan for worst case.
    bmwpowere36m3Zman
  • bmwpowere36m3
    bmwpowere36m3 Member Posts: 512
    Floating engineered floor, R3? I'd think closer to 0.5... For 3/8 to 1/2" thick.
  • bmwpowere36m3
    bmwpowere36m3 Member Posts: 512
    So you spend a little more on tubing and manifolds.... In the scheme of things I'd say a minor cost. Being embedded in concrete I'd rather be dead-on or slightly conservative if someone decides to change their mind and then realizes the required water temps are thru the roof to heat the space.
  • Gordy
    Gordy Member Posts: 9,546
    edited December 2015

    Floating engineered floor, R3? I'd think closer to 0.5... For 3/8 to 1/2" thick.

    Read original post.

    If the installer does double layer plywood, and then 3/4" hardwood. Recommended hardwood install method for hardwood flooring. That's an r 2.5. If the use 1/2" 2 layers with shorter nails that gets it down to just under r 2
  • Gordy
    Gordy Member Posts: 9,546

    So you spend a little more on tubing and manifolds.... In the scheme of things I'd say a minor cost. Being embedded in concrete I'd rather be dead-on or slightly conservative if someone decides to change their mind and then realizes the required water temps are thru the roof to heat the space.


    Walk carefully down the over design path. An extra grand is enough to throw some into an entirely different choice that leaves the installer with out the job.


    For what it's worth over concrete coverings can vary widely in the unforeseen future. What worked for bare concrete may have lack luster performance for future owners that think they need carpet over a neutral concrete surface.
  • bmwpowere36m3
    bmwpowere36m3 Member Posts: 512
    I hear ya Gordy... but I also can't imagine bare concrete inside a home, even polished. Maybe a work space or garage, but living... to reach his own I guess.
  • bmwpowere36m3
    bmwpowere36m3 Member Posts: 512
    Double plywood over concrete, hmm. I guess you learn something new everyday. If it were me, I wouldn't be pouring concrete as the subfloor then.... barring a basement or on-grade construction.

    So no option to have a floating hardwood on concrete without some plywood underneath?
  • Gordy
    Gordy Member Posts: 9,546
    Go to concrete networks web site. They can do some pretty amazing staining, and thin coats now days the imagination is the only thing holding someone back.

    Add a neutral foot comfort, and it can be quite pleasing.
    bmwpowere36m3Zman
  • Gordy
    Gordy Member Posts: 9,546

    Double plywood over concrete, hmm. I guess you learn something new everyday. If it were me, I wouldn't be pouring concrete as the subfloor then.... barring a basement or on-grade construction.



    So no option to have a floating hardwood on concrete without some plywood underneath?


    There are always options. Typically that would be a gymnasium floor assembly.
  • NYplumber
    NYplumber Member Posts: 503
    If there is going to be two layers of plywood plus flooring, the insulation r value should be higher then normal to direct heat flow. The wood will hinder the heat transfer.

    Size for worst case and lower water temperature as needed. Make sure to install floor sensor to protect the finished floor should it turn out to be wood.
    :NYplumber:
  • I told the contractor that he needs to know if he is using hardwood. If so, we would probably use a product like Warmboard-R which (I believe) can be screwed directly into the (well-drained) slab.

    Yes, I agree that a concrete slab is not a very inviting finished floor, but that's often done these days. They could easily upgrade to tile as well.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    Enter the project into the Uponor ADS software and you'll have your answers. You'll also be able to do "what if?" Having done hundreds of slab on grade projects, I'd rather have more tubing on 6 or 9" centers which lowers the required loop water temperatures, than struggling if the floor coverings change. I'd also be using pre-engineered hardwoods rather than the Bollinger method (2sheets of ply), Sometimes the owner "must"have regular hardwood. That can become a problem.
    SWEI
  • neilc
    neilc Member Posts: 2,663
    if I were king , , ,
    spend all their money,
    put tubes in the concrete, for concrete,
    then when they choose the wood floor,
    abandon the concrete tubes, and install the manufactured tube underlayment, and connect to that system.
    what are they doing about slab insulation(s) ?
    known to beat dead horses
    SWEI
  • Gordy
    Gordy Member Posts: 9,546
    Just the contractor I would want to hire........good thing your not king.
  • neilc
    neilc Member Posts: 2,663
    I have wise **** moments time to time.
    known to beat dead horses