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Time to dry a 4" slab in the Ozarks ?????

    What is the recommended length of time  to allow a 4" thick slab 

( 24'x36' )  to dry before turning on the radiant heat?




  • Leo_G
    Leo_G Member Posts: 89

    According to the concrete guys I've talked to, min. 6-8 weeks. They prefer 12 or more. If you drive the moisture out to quick, you can get spalding or even the concrete turning "dusty".
  • Curing or Drying?

    I was waiting for one of the radiant guys to answer this. I can tell you a bit about concrete though how  the application of radiant heat applies to new concrete I have no clue.

    With concrete there is a difference between "curing" and "drying".

    "Curing" - Concrete needs to be kept moist during the curing phase. This is usually done by applying a special sealer to keep the moisture in or by covering the slab with damp (and keeping them damp) burlap sacking. If it drys out, the curing immediately stops and the concrete doesn't reach full strength.  The majority percentage of strength is reached in the first seven days and continues then  to  slowly again more strength after that. After 28 days, concrete is considered to have reached its full strength and be cured.

    "Drying" - The old thumb rule I was taught is that after` you stop watering it, concrete will dry out at one inch per month.  My experience had been with epoxy coating concrete and we left a 4 inch slab for 12 to 16 weeks to "dry"  before sealing it with epoxy. (The longer, the better)   This seems to be in line with what Leo recommended.

    I don't know what your time factors are, normally there is quite a bit of time after the slab is poured till the heating system is fired up. I'd wait as long as possible- at least 8 weeks and then I think I'd bring up the heat very slowly in the slab as sort of a "break in" period.  You might want to see if you can get a better qualified answer on this and check around with guys that pour radiant slabs. Any of your radiant guys got some input on this? I'd also be interested.
  • Rhomar Mike
    Rhomar Mike Member Posts: 11
    dry time

    Leo and  Rod, thank you very much.  i'm certain i can wait a while, or at least until  curiosity gets the best of me to try it out. 

    Thanks  again,


    Commercial Sales

    Rhomar Water Inc
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