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Where to attach the window nailing fins in a rainscreen assembly?

user-735982 | Posted in Green Building Techniques on

Hi there,

Developing a detail for Northern California. We don’t have any exterior foam in this project. The house has plywood sheathing with 3/8″ furring strips to create rainscreen void.

Do we place nailing fin for Marvin (1″ nailing fin) window directly to the sheathing or furr it out 3/8″ to match the rainscreen? We are cladding the building with 3/4 horizontal wood siding. I’m thinking directly to the sheathing and then have deeper window trim.

Thanks so much…

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  1. davidmeiland | | #1

    That's what I would do. Install and flash the windows to the sheathing, along with the WRB. Apply the furring over the WRB. Think of the whole thing as siding and trim with the furring attached to the back of it.

  2. dave northup | | #2

    That is how I have done it in the past as well... Just double check that the desired trim used will not project out past the window frame with that added 3/8" - that looks a little weird...

  3. 5C8rvfuWev | | #3

    Could one of you explain the preference? Any technical reasoning?

    TIA, Joe

  4. davidmeiland | | #4

    Joe, it is much easier to flash windows if the flanges are in the same plane with the WRB. If the flanges are out beyond the WRB, the flashing tape has to become three-dimensional, with some folding required at the corners. It doesn't suit my obsessive-compulsive personality.

    The only way I've done rainscreen is with HomeSlicker, which is 1/4" thick. Nothing changes about the window install. You tack the Homeslicker up right before siding. If I was doing something with 3/4" furring behind the siding, I might have to reconsider to avoid burying the windows too deep in the trim, as Dave N is saying.

  5. dave northup | | #5

    Exactly - it is much easier to integrate flashing into the WRB when it is all on a flat plane...

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