GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Closed Cell Foam in Old Wall Assembly

Ryan Lewis - Zone 4A | Posted in General Questions on

Can someone point me at the rules for using foam on a wall assembly? My contractor came to spray the ceiling (finally!), it all went well there, however he also sprayed 4″ closed cell HFO foam in a small section of a 2×4 wall. The wall assembly is “old” stucco + tar paper adhered to shiplap. See the attached section. 

I’m concerned about moisture now since this wall cannot dry to the interior. Do I need to ask the contractor to remove this small section? See photo below.

Is there any risk to the exterior stucco or shiplap?

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.

Replies

  1. Ryan Lewis - Zone 4A | | #1

    Bump.

  2. Expert Member
    DCContrarian | | #2

    Closed cell spray foam is vapor impermeable. You want the wall to be able to dry in both directions from the foam, otherwise you have a vapor trap.

  3. Expert Member
    Zephyr7 | | #3

    You probably won't have a problem here. On the inside, you should have drying to the interior. On the exterior, the only thing to think about is that stucco. I don't have much experience with stucco, which is why I didn't comment before. Close cell spray foam in thick enough layers -- which you have here -- is a vapor barrier. If you have an air gap in the exterior of that wall assembly that is probably enough to prevent any major issues though, as long as the gap is vented to the exterior somewhere.

    Bill

    1. Ryan Lewis - Zone 4A | | #4

      Right there is no air gap. It is literally stucco attached to felt paper attached to wood — now attached to foam.

      I’ve asked the contractor to grind it out — down to 1” or less.

      1. Expert Member
        Zephyr7 | | #5

        If you're going to have the spray foam removed, you probably want to remove pretty much all of it -- leave NO layer. A little bit of remnant foam here and there is OK, but try to avoid having an actual layer as much as possible.

        Bill

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |