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Community and Q&A

When re-siding, what to do about window flashing?

Jason Adams | Posted in General Questions on

I’m residing my house in eastern Iowa, climate zone 5. I’m also adding 4 inches of exterior EPS insulation. What I’ve noticed when pulling the siding off is that the previously-installed windows were done…well, not terribly, but not up to what I’ve seen described here as best-practice. Here’s what I noticed: 

– a bead of sealant was used underneath the nailing flange on the top and sides, but not the bottom  
– a sloped piece of cedar siding was installed in RO, and then 3M 8067 flashing tape was installed over it, about 6” turned up at the sides of the RO

– the corners of the RO appear to be handled the way that the 3M 8067 instructions dictate
– the side and head flashing over the nailing flange appear to be installed as per the 3M 8067 instructions in terms of length and order (but taped to the sheathing, not the WRB–see below “concerns”)
– the WRB tar paper is lapped for each course appropriately and taped on the vertical seams at the window flange
Here’s what concerns me: 
– the WRB is tar paper, and is lapped over the top of the side nailing flange+flashing, not underneath the flange, or wrapped into the side RO 
– the WRB is lapped over the bottom nailing flange+flashing, not underneath
Given that I’ll be installing 4” of rigid foam, the windows will be “innie” windows and even more protected.  Do you think it’s low-risk to leave everything as-is, or do I need to remove the windows and re-do everything?  Seems like the highest risk right now is if water gets into the sill, and then drains out behind the WRB. 


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  1. Expert Member
    Akos | | #1


    That sounds like they did a proper window install where the window goes in first and the WRB afterwards (you can google the manufacturers instruction to check the details to make sure).

    You would still need proper head and pan flashing to get the water out past the foam/rain screen/siding. These folks show some pretty good details of what you need (somewhere towards the end).

  2. Jason Adams | | #2

    Thanks Akos. I guess what had concerned me was that I've seen multiple videos/articles where an installer will wrap the entire RO side jambs with the WRB or peel-n-stick flashing, as well as install the WRB under the sill flashing peel-n-stick. So since I didn't have those two things, I was concerned. It sounds like this job was done fairly well, which I'm glad to hear.

  3. Brendan Albano | | #3

    You might want to post a photo of this item: "the WRB is lapped over the bottom nailing flange+flashing, not underneath"

    That doesn't sound quite right, but it's easy for things to get lost in translation when described in words on a web forum.

  4. Expert Member
    Malcolm Taylor | | #4


    These videos may allay your concerns. One shows the WRB applied first, the other after.

  5. Expert Member
    Peter Yost | | #5

    It's all about exposure when assessing risk; see this recent Q&A Spotlight blog:

    Assess your exposure as best you can and at least consider actually testing a window or two.


  6. Jason Adams | | #6

    Thanks all for the replies.

    The videos that Malcolm posted put me more at ease. The only thing that wasn't done is to install that WRB "apron" that goes under the sill flashing tape. But, it seems like I can also consider how these windows will be "innies" and inset with 4 inches of foam. I will be sure to install the foam carefully with all of the required flashing details.

  7. Paul Kuenn | | #7

    You may want to peak at the story I wrote with photos and ask me questions if needed.

    4" of foam up to the window frame can certainly protect well.

  8. Jason Adams | | #8

    I wanted to follow-up as I was tackling this project now.

    I decided to remove the existing WRB tar paper and get down to the sheathing and the window flashing.

    In picture 1, you can see how when the new window was installed, there was no WRB put underneath the sill flashing. As I mentioned in the original post, a piece of beveled siding was installed under the window, and the flashing was run over the top of the sheathing.

    Since I didn't want to remove the installed 3m peel n stick flashing to get under it with my WRB (#30 felt), I installed a second piece of flashing tape that butts right up to the first. I also then lapped the side jambs again , running it over the top of the first piece that I installed. That's shown in pic #2.

    Then in pic #3, you can see that I slipped my WRB under the flashing tape. I think that this continually directs water to the outside. I will of course keep working my way up the wall with the WRB taped to the side jambs.

    In pic#4, you can see the entire application of the WRB. I overlapped the WRB that was under the window and ran it up to the side jambs. Then I taped the horizontal seam.

    Thoughts? I know it's not perfect. Just hoping to make the best of it.


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