Detailing WRB with Flanged Window
joenorm
| Posted in General Questions on
Flanged window install detail
Is it acceptable to not fold the WRB into the sides of the window opening?
I have found this detail makes air sealing from the interior more difficult.
Is there a method where all flanges of the window are directly against framing instead of having WRB sandwiched in-between?
In this case I could see cutting out the whole opening in the WRB instead of doing an I or X cut.
Thoughts and/or links appreciated.
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Replies
Every window manufacture provides detailed instructions on how to install their window and disregarding them would be foolish as well as a code violation that voids the warranty.
The point of the WRB is that it needs to be installed much like shingles so the at every joint all the water gets redirected back to the exterior.
Walta
joenorm,
Yes, this works fine: https://www.youtube.com/watch?v=SqP4liutJFs although for some reason the Tyvek videos all omit a metal head-flashing.
Another alternative is to install the WRB first, but just run it into the jambs an inch or so.
"Cut back" or "window first" both do not include fold in.
Benjamin Obdyke, like said, they aren't window makers:
https://www.youtube.com/watch?v=IJKqzyQYoTo
Benjamin Obdyke FlatWrap has all three methods (fold in, cut back, and windows first) in their instruction pdf found on this page: https://benjaminobdyke.com/product/housewrap-flatwrap-hp/
The liquid flashing WRB on rough opening has moved from only 6 inches up from the bottom sill to the entire rough opening, from what I've read.
Another thing that might guide you is googling 6 inch tape vs 9 inch tape. I can't remember details, but it seems like we settle on 6 inch, bu there is a history of 9 - 12 inch tape for flashing at the nail fins. I split the difference and did 9" on the side/top fins at no real cost. In reality, if there is no difference, one could say 4" tape is sufficient to cover a fin and be on the WBR...so there is something to 6" being the current norm...
I found that it was difficult to do the cut back method and have liquid flashing seal perfectly onto the less than perfectly flat house wrap with my 2" cut back method. While mostly good, not always.
It seems that most feel what house wrap cut method is sweating the details. I'm not so sure myself that one couldn't be technically superior and least likely to fail.
I paid a lot of money for a “high end” Marvin window install using the Marvin / OSI method. In my case they did the cut back method with the flashing tape wrapping into the RO. It looked good…time will tell.
I am just wondering what the point is of folding the WRB back into the window opening?
Why not instead of an "X" or "I" cut would you not just fully cut out the entire window opening of the WRB?
The top can be lapped over the window and the sides and sit get tape.
There are many ways of skinning that cat and they all work if done properly.
My way is to cut the WRB about 3/4 to 1" larger than the rough opening. You flash the rough opening with flex tape which goes over the sides and the bottom, lapped at the top by the WRB. Since the tape is adhered to the sheathing this does dual purpose as it now provides the air barrier continuity to the rough opening.