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No Flashing on Windows with Tyvek Seam Taped to Nail Flange

Orangetractorkid | Posted in General Questions on

I put an addition on my house last fall and the contractor installed the nail fin windows directly to the osb sheathing without any flashing around them. He then wrapped the house in tyvek and tyvek seam taped around the nail fin overlapping from bottom to top. I questioned him on this and he said he’s been doing this thirty years and has never had one leak. I asked about flashing and he said I could flash over the tyvek.

should I remove the seam tape and flash the nail fin to the osb sheathing and then over lap the top fin with tyvek? What’s the best option?

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  1. user-5946022 | | #1

    He said he has been doing it thirty years without a problem because HE has not had a problem. The Homeowners he installed this for have undoubtedly had problems, but they are unlikely to call the guy that created the issue via poor quality to come back and fix it after x years...

  2. Orangetractorkid | | #2

    I was thinking of removing the seam tape from the flange and using flashing tape around the nailing flange onto the osb. I would then overlap the tyvek over the flange. Would this be a better option?

  3. Expert Member


    There are several ways of installing flanged windows that work fine, some with the rough opening papered, some with the window installed directly on sheathing. What matters is how the whole thing is done.

    Here are a couple of short videos illustrating two approaches. Neither shows a metal head-flashing, which in some regions is used and in others not.

    I agree with CL though. There aren't many things I'd like my builder to do the same way they did thirty yers ago.

  4. Orangetractorkid | | #4

    Thank you for the responses. I have also seen those videos and watched them from past posts. In watching the video where the WRB is put on after the windows, it shows a piece of WRB being placed under the sill. I fortunately do have a sill pan but no flashing or wrb tucked underneath. I’m trying to fix what I currently have, without pulling the windows out as they are 6x6. Would you recommend flashing the sides and top and leaving the bottom And then taping the wrb around it?

  5. Expert Member
    AKOS TOTH | | #5

    If you have one of those pre-fab sill pans, you want to tuck the WRB in behind it. You might be able to pry up the nail fin on the bottom enough to slide in a piece of house wrap between the sill pan and the OSB. Have this lap over the houswrap on the bottom of the window. Tape the whole thing with a couple of 1/4" gaps to allow for draining.

    If there is nothing in the rough opening just a wood sill pan, you should fix that. All windows leak eventually, without proper flashing+drainage it will rot the framing eventually. All old houses I've replaced windows on without any flashing details had at least some soft spots on the bottom of the rough opening.

  6. Orangetractorkid | | #6

    It has a made on site aluminum sill. Not sure how far it extends down, I’ll have to check. I’m guessing it won’t extend down very far.

    When you see leave a few 1/4” gaps, do you mean only along the bottom?

    Thank you again for the responses.

    1. Expert Member
      AKOS TOTH | | #7

      It sounds like most things were done properly. It makes sense that all falshing should be properly lapped by the WRB, you always want water to move out and away from your structure.

      The gap is on the bottom. You need some way for the water to eventually make it out from behind the window nail fin.

  7. Orangetractorkid | | #8

    My plan going forward is to remove the tyvek tape from the nail flange, try to push tyvek under the sill pan, use 3m 8067 tape on the sides and top, then wrap the tyvek over the flashed nail fin and under on the bottom piece.

  8. Orangetractorkid | | #9

    I haven’t fixed the issue yet but I’d like to point out Its the first day of rain and water got behind the tyvek and is coming in the top of the window. Big surprise.

    1. insaneirish | | #10

      Did you reach out to the contractor?

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