Why can't polyiso be used under concrete?
Polyiso Insulation Board
Insulation
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Open Aug 24, 2025 - 09:07 AM
1answer
Answer
Aug 24, 2025 - 03:04 AM
Polyiso insulation is porous and can absorb moisture from the soil which could reduce the R-value and eventually degrade the foam. Use XPS or EPS closed cell foam for below concrete slabs as they will not absorb moisture.
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Polyiso Insulation Board
Polyiso Rigid Foam useful for all sorts of projects - walls, roofs. (not for use under concrete)
IN STOCK at our warehouse in Fairfield, Iowa
Most are NEW Factory Seconds
Retails for $60 per sheet or more.
4' x 8' and 4' x 4' Sheets:
Thick R-Value Price...
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