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Closed cell spray foam over moist brick and mudsill

WildBunchFarm | Posted in Green Building Techniques on


A duplex I recently purchased has a moist crawlspace including moist brick and water-stained mudsill (see pictures).  I believe most of the problem comes from missing or poorly placed downspouts.  The area around the foundation is also poorly sloped.  I intend to fix all of those problems.  

Recently, a contractor cleaned out the crawlspace and placed a vapor barrier on the ground.  He intends to use closed cell spray foam (Demilec HFO Heatlok High Lift) up to R-10 onto the brick foundation, mudsill, and rim joist.  However, the brick foundation is a bit moist.  I’m thinking I have to put some dehumidifiers down there to dry out the foundation and mudsill before they apply the spray foam.  Is that correct?  

Thanks for any advice.

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  1. Expert Member
    BILL WICHERS | | #1

    If the foundation is wet you risk problems with the spray foam not adhering properly. It is a good idea to try to dry things out before applying spray foam.

    If you expect to have ongoing moisture issues with that wall you’ll want to allow a way for the wood structure to dry if you can’t install a capillary break.


  2. WildBunchFarm | | #2

    Thanks, Bill. I'll solve the moisture problem before I apply the spray foam. Capillary break would be hard to apply in this situation. I may just install a dehumidifier for a few weeks and get a mason to repoint the outside to keep moisture from being sucked in from the outside. Lots of gaps in the foundation currently.

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