Basement subfloor foam?

Discussion in 'Remodel Forum & Blog' started by Twoplanker23, Dec 30, 2018.

  1. Twoplanker23

    Twoplanker23 New Member

    Joined:
    Dec 30, 2018
    Location:
    Ontario
    I am in the middle of a Reno on a walkout basement in muskoka. Due to height issues I can only lay down 1/2" xps with 5/8" t&g ply on top as a subfloor.

    Is this enough insulation to prevent moisture issues? Will it be safe to lay engineered hardwood on top of this?

    It is a lakeside home but the room will be air conditioned in the summer so humidity will be controlled.

    Any help will be greatly appreciated, thank you in advance.
     
  2. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Half inch XPS would be marginal for dew point control if not air conditioned in the summer, if air conditioned it shouldn't be a problem. An indoor relative humidity of 50% @ 24C would generate slight vapor pressure from the room toward the slab, but there would be no moisture accumulation on the bottom side of the subfloor, which would be well above the dew point of the room air.

    Unless you know for certain there is a vapor barrier under the slab, installing a polyethylene vapor barrier between the foam and subfloor would also be a good idea to protect the subfloor from ground moisture. The vapor permeance of half-inch XPS is still a bit too vapor open on it's own.
     
    Last edited: Dec 31, 2018
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  4. Twoplanker23

    Twoplanker23 New Member

    Joined:
    Dec 30, 2018
    Location:
    Ontario
    Thank you Dana, happy New Year!
     
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