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Polyiso for basement floor?

jimruss75 | Posted in General Questions on

I have an unfinished basement with essentially a dirt floor (with a thin layer of crumbly cement) and a rubble foundation. I’d like to dry the basement by installing 6 mil sheeting on top of the floor and up the basement wall to the sill beam. I have a stack of 3” reclaimed polyiso insulation left over from a roofing job. Can I lay the polyiso on the basement floor on the sheeting and then cover ut with 1/2” plywood?

The basement is only used for storage. I know polyiso can not be used for ground contact, but can I use it on the basement floor Over a vapor barrier and be walked on?  Thanks.

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  1. GBA Editor
    Martin Holladay | | #1

    EPS would be a better choice for this application -- because crawlspace floors can be damp, and it's possible for water to puddle on top of your polyethylene in some circumstances. Polyiso can absorb water more readily than EPS.

    All of that said, if you know that your crawlspace floor is dry and puddle-free, and if the polyiso is free -- using it makes environmental sense and economic sense.

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