Flashing dormers using peel-and-stick bowties
Peel-and-stick membranes allow a level of protection and redundancy never before possible when flashing a dormer. The process involves some forethought, mainly because a portion of it has to be done before you’re finished framing.
For example, the first pieces of membrane have to be installed after the wing walls are in place, but before the roof is framed. That’s because the rafters’ overhang makes it almost impossible to get the membrane in place at the critical juncture where the top of the cheek meets the main roof. I like to use Grace’s Roof Detail Membrane because it comes in a convenient 18-inch width and there are ripcords embedded beneath the release sheet which can be used to separate it into more manageable sections making it easy to peel only the paper you want to remove at a given time.
By following the steps below, you can help ensure that your dormers will be watertight.
To learn how Rick Arnold builds and installs doghouse dormers, see his article Doghouse Dormers in the April/May 2007 issue of Fine Homebuilding.
— Photos by Roe A. Osborn