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radiant on slab with wide-plank white pine?

LVV Member Posts: 4
I searched for posts on this topic and didn't find any exactly specific, so sorry if this is redundant, but we are hoping to install some wide-plank white pine we cut down about a year ago and has been stacked on stickers ever since. We had it cut into boards (obviously), and now we want to get it milled and put into a sunken living room on a concrete slab (room used to be a garage), there seems to be some subflooring underneath (we pulled a corner of carpet up and found wood at least), and I would really like to install radiant because this is the one area not warmed by the woodstove, and one of two long, baseboard registers is behind the couch (i.e., not effective). However, we're hesitant to do this because it may cause extreme cracks, cupping, etc. with nailed-down wide-plank pine with the heat source so close, and we're not sure about doing it over a slab and raising the floor up more than an inch or two at most. I've heard mixed reviews about doing radiant with pine and how well the pine reacts (we would get it acclimated to inside temps first). I've heard positive reviews and negative about pine being great for this. I'm wondering the practicality of using the radiant with these boards and the best option for radiant (electric pads, hot-water panels) in this scenario, particularly given that it's on a slab and we do not want the floor a foot higher and do not want to spend a small fortune. Any advice would be great. We are in New England, so humid in the summer and cold in the winter. I am a new home owner with extremely minimal understanding of technical terms, so please talk slowly. Thanks.


  • SWEI
    SWEI Member Posts: 7,356
    How far can you raise the finished floor level

    above the existing slab?

    I'm assuming it was poured on grade.  Please correct me if that is not the case.
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    edited October 2013
    wide planks and radiant

    Read the guide and it will answer most of your questions.


    Wide planks can be difficult to deal with. They tend to cup (unless they are pre-engineered) The boiler control needs to be carefully modulated (ODR and mixing temps) to prevent the floor temp from exceeding 85 at design temps. Usually 2 sheets of ply are floated under the planks to buffer the slab temps (The Bollinger method) and the planks nailed to the top sheet. Expect cupping and shrinkage if not done right.
  • LVV
    LVV Member Posts: 4

    yes, on the existing slab, which is slab-on-grade, as far as i know. i've never been told this by previous owner or anyone, but i can't imagine what else it could be. if there is some way to tell by looking at it from outside, i could try that. i know there isn't a crawl space, however, there is an ash pit for the fireplace down under the fireplace at the very end of the house (it can't be emptied, and we'll eventually just fill in because it has some plywood construction and isn't ideal for safety reasons).
  • SWEI
    SWEI Member Posts: 7,356
    Lay down some XPS foam

    At least 2" -- 4" is even better if you can make that work.  Then top with your favorite dry-floor system (the RPA guide Paul linked to above covers those quite well.)
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