GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Help with re-flashing leaking windows

DIYJester | Posted in General Questions on

First off, these are outies installed in a 2×6 wall with 4″ of xps on the exterior.

Well, I’ve installed a handful of windows and luckily before I got all of the siding up we had a really nasty storm and got about 5″ of rain in two days. During the storm we had sustained winds which blew the rain horizontally against the wall I had yet to put the siding up on yet. Low and behold I saw a few drops of water on the peel in stick flashing in window pan. I had not foamed or sealed the sills from the outside to allow drainage, and had yet to seal from the inside, so I was able to see this well. There were only a few drops of water, but we all know it will get worse and now is the time to fix it right.

I have a good idea where I went wrong, I used furring strips around the window buck box I built and pinned the WRB behind this instead of in front of this. I used peel and stick flashing from the top of the furring (stuck to wrb), over furring and then to the nail fin. I put too much stock into the peel and stick flashing and WRB tape in that it would be able to carry the water over the furring strip. This allows any water the tape and flashing misses right behind the furring strip to land directly behind the nailing fin .

Would it be possible to slice the WRB above the windows and layer a new piece beneath and behind the first piece to allow the the drainage plane to be in front of the furring/nail fin? Any other ideas would be great. I really don’t want to have to pull all the furring down to put up a new layer of WRB.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. GBA Editor
    Martin Holladay | | #1

    We need a sketch or a photo.

    The basic principle is that you need a 4-inch lap at horizontal seams in your WRB. If you can create such a lap, there is no problem with slitting your WRB and making alterations.

    One other point: if a few drops of water leaked onto your sill pan flashing -- that is, the flashing on your rough sill -- you don't necessarily have a disaster on your hands. If the water is on your sill pan, that's what your sill pan is for. It keeps your rough sill dry in case your window leaks. In most cases, those drops of water evaporate.

  2. DIYJester | | #2

    Thank you for the fast response. The basic concept around the windows from outside in is:

    window nailing fin, furring strip, WRB, foam (2 2" layers taped and gaps filled), OSB. I then used peel and stick flashing from the window's nailing fin,over the furring strip and adhered to the WRB. It must have found a poorly adhered section and drip down in.

    Edit: I think I found where it was coming it. there may have been a small funnel created with some of the tape and the corner of a piece of furring I put up before my wife taped the edges of the flashing.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |