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Vapor/Air Barrier for Open-Cell Spray Foam, Insulation Board, and Stucco Assembly

gregory_harper | Posted in GBA Pro Help on

Question regarding proper use of vapor barrier and air barrier in residential construction 40iles form the gulf of Mexico. wished
I am not familiar with correct use of insulation board. Proposed wall assembly is from inside out:
-gypsum drywall
-painted gypsum board
-open cell spray foam insulation between 2×4 studs
-1/2″ oriented strand board
-plastic house wrap (Tyvek)
– 3/4″ insulation board (ESP?)
– portland cement stucco on expanded metal lath

Can we eliminate the housewrap if we use an approved polyiso board?
Do we need a layer of building paper or felt over the insulation board and behind the metal lath?

My stucco sub wants to place 15# felt paper behind his lath.

Would someone please critique this assembly? Seams like a lot of layers. Thank you.

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Replies

  1. GBA Editor
    Kiley Jacques | | #1

    I'm giving your question a bump. While you wait for builders to share their opinions, check out this episode of the BS* + Beer Show: “Choosing and Using Water-Resistive Barriers.”

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