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Stucco over existing masonry – drainage plane?

BillFrank | Posted in General Questions on

We are building a new house on top of some existing garages in zone 4a. The top two floors of this house are wood framed construction. The existing 1st story is masonry, brick and block. The wood framed part is offset from the back masonry wall which is right on the property line. I am the general contractor.

Do we direct apply stucco to the back masonry walls or do we decouple the stucco putting it over some sort of drainage plane? We have a great drainage plane on the stucco over wood. What makes me hesitate is that in this town stucco is always (?) applied directly to existing masonry. I don’t know why I don’t have any input from the architect. The client is great and super versed in this stuff but as a builder it’s my job to give some credence to traditional standards and practices. Usually the architect gives the wall assemblies but not this time.

Space behind these masonry walls will be conditioned but not fully conditioned. No AC. The living space above is to passive house standards.

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  1. BrianPontolilo | | #1

    Hi Bill.

    My knowledge of stucco is limited, however, I believe that it is common in some areas to apply stucco directly to masonry surfaces, and the 2018 International Residential Code allows it. With existing masonry, I would imagine that the structural and surface conditions would be a factor. Hopefully, some GBA members with personal experience with stucco will drop in and help with your question. If you do decide to install a drainage plane, this may be helpful: Rainscreen Products for Stucco Installations

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