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Community and Q&A

Spalling foundation and rigid foam application

nynick | Posted in Energy Efficiency and Durability on

My old home has an old poured concrete foundation in part of it and a fieldstone foundation in another part. The plan was to CC SPF the entire thing until I got the estimate….holy inflation Batman! A conditioned basement is the goal.

The concrete portion has a spalling effect, where chips and dust fall off the walls. The basement is very dry otherwise. Would it be ok to use rigid foam on the concrete walls even though are spalling? This could save a bunch of money over CC. I would use CC SPF on the fieldstone anyway.

I am planning some kind of Delta FL type flooring treatment with vinyl plank flooring, if that matters.



What do you guys think?

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  1. Expert Member
    PETER G ENGLE PE | | #1

    It might help to know the age of the foundation - very old concrete sometimes behaves differently than newer concrete. If the spalling is just here & there and seemingly related to dampness, you're probably OK just fastening sheet foam over the foundation. If you can get recycled foam, you don't create any new carbon or environmental issues. You will have to use anchors because the dusty/spalled concrete surface will not work with adhesives. PlastiGrip anchors are one of the more common products.

    1. nynick | | #2

      Thank you Peter. My best guess is that the concrete foundation walls are almost 100 years old. Very thick too. The fieldstone walls could be 150-170 years old.

      The spalling is quite extensive.

  2. Expert Member
    PETER G ENGLE PE | | #3

    Very old concrete was generally mixed on site and the mix and materials used are anybody's guess. By insulating the interior of these walls, there is a remote chance that the walls will freeze more often and freeze/thaw cycling can cause damage to low-strength concrete. But you mentioned that they are very thick. If it has taken 100 years to cause the damage you see right now, how long will it take for the spalling to have any serious effect on their strength? At 100+ years old, the foundations have already reached the end of their rated useful life. You might consider insulating them and leaving the problem of wall repair/replacement for someone decades from now.

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