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Community and Q&A

Stucco lath over 4″ foam

user-714815 | Posted in Green Building Techniques on

For a new home in the southern New York, I am trying to figure out how to attach lath to four inches of polyiso for hard-coat stucco. I have read every discussion I can find on this site as well as Lstiburek’s recommendations for air gaps and building papers, but I haven’t seen mention of how to reconcile the staples for Spiderlath or the nails for metal lath installed every 6-8 inches and exterior foam. I am avoiding PVC and therefore synthetic stucco/EIFS. Thank you for your input!

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  1. Doug McEvers | | #1

    I think you might have to add a layer of plywood over the foam, attaching wire mesh with 7 or 8" screws sounds like trouble to me. We are painting ourselves into a corner with the thick foam sheathing in my opinion, making a quality exterior finish almost impossible.

  2. Armando Cobo | | #2

    For what is worth, in NM, codes do not allow installing stucco on more than 2” of foam, unless you have an Engineered design and stamp. It has to do with the lack of proper stucco and lath attachment to the wall. The experience in NM is that nails and screws cannot handle the cladding weight years on out. Maybe a sure option is to reduce the exterior insulation to 2" and increase the inside insulation to what you are trying to achieve. At least it could be less expensive.

  3. 9eNqwibREM | | #3

    Just curious, how did you proceed with your stucco over rigid foam? I'd like to add rigid foam to my exterior, with a portland/traditional three-course stucco, but not sure if this combination is really viable.

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