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

Material to Install Between Foam Board and Wood Cladding

jeuteneier | Posted in General Questions on

I had another post explaining that I am putting up cedar fence boards for wall cladding and just butting them together in my 7×10 office. My walls are insulated with cut and cobble foam boards (see pic) with a mixture of fiberglass faced polyiso, XPS, and EPS (all salvaged).

I expect the boards will separate a bit which is fine, even desireable, but I want it to be a dark color that is revealed. I had planned to put 1/2″ foam boards then paint those but I’m certain there is a simpler solution.

Options I’m considering:
Simply paint the foam insulation black w latex paint
Red rosin paper stapled over insulation (the red color is fine)
Roofing felt – I have a bunch of #30 but that’s probably too thick and not sure if I’ll be creating a moisture problem. Not too mention the smell on hot days but maybe that will dissipate quickly?

Open to other ideas. I’m aiming for simplicity.


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.


  1. Ryan_SLC | | #1

    Cladding is exterior by definition.

    Rtech says for interior a fire barrier (1/2 drywall for example) has to cover them, along with all building code I am sure.

    Cedar isn't a fire block material?

    I think you have a no go idea.

  2. jeuteneier | | #2

    Ah, thanks Ryan. I thought it just meant covering. Noted.

    So you're saying wood can't be installed directly to interior studs? While normally a stickler for doing it "right" I'm good with a more practical solution in this case. It's a tiny 7x10 backyard office.

  3. Ryan_SLC | | #3

    Oh. I am a dad, not a builder.

    However, I researched the crap out of foam insulation interior for my cathedral ceiling I still haven't figured out how to get to R-38.

    100% RMax and Rtech (both Henry?) and all foam interior must be behind a fire barrier. Foam not only melts in a fire, that foam board in your picture is the 2nd main component of napalm. To say it's combustible doesn't even begin to describe what styrofoam does when on fire. You'd be smart to get 1/2 drywall up and then do the cedar. So cedar could be the interior finish (though I also wonder if we're both forgetting that drywall adds rigidity to a walls...), but you HAVE to cover rigid foam on the interior with a fire blocking material. Wood isn't that :)

    Inspected or not, I wouldn't do it...

    1. jeuteneier | | #4

      I appreciate the recommendation. I may end up doing just that but hoping there's something easier.

      1. Ryan_SLC | | #5

        I don't think there exists an easier or thinner material than 1/2 drywall for the fire barrier. Even that orange foam you've used isn't actual fire barrier. Burns like the rest of foam. Just orange to mark that you have closed oxygen traveling between closed areas...

        Good luck.

  4. paulmagnuscalabro | | #6

    Probably the easiest & cheapest thing to do is just buy a few rolls of black weed mat. Staple it up behind where your boards are going, put the boards up, and you're done.

  5. jeuteneier | | #7


    I installed 1/2" drywall or plywood or OSB (using up the remaining materials I had) over the insulated stud bays. Now I still have the issue of getting a black finish for the gaps in my cedar planks.

    I assume any of these would work:
    1. Paint the walls black
    2. Put up red rosin paper (I don't mind the dark/burnt red color and I need a roll anyway for flooring underlayment)
    3. Black weed mat (thanks paulmagnuscalabro that's a clever idea)
    4. Black duct tape (I don't plan to use this but thought I'd complete the list in case someone in the future has a similar project)

    I'm leaning toward the red rosin paper just to be fast.


Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |