May 22, 2018
Roofs peel off from the edges, so it is critical to hold them tight
With the roof deck sealed on the outside, we turn to flashing the edges with metal and membranes
- Metal drip edge flashing should go over the taped eave. The uphill leg should extend at least two inches up the roof, more is better. For long runs that require multiple pieces of drip edge, overlap the seams the opposite direction of the prevailing winds — at least two inches for code, and three inches for Fortified Home Program.
- Install rake pieces to overlap the eaves, nailing every four inches, staggered up and down.
- Valley metal goes over the sealed valley with only the top of the valley metal nailed into the deck. Other nails trap the edge of the metal, allowing it to expand and contract between day and night.
- Tape the edges of the valley metal.
- You can also seal the rake edge metal and the eave edge too. The eave needs extra protection from water and ice for two feet inside of the outside of the wall. That usually means more than one strip of peel and stick membrane. Some people cut rolls in half to save materials.
- An eight-inch band of roofing cement at the bottom edge and up the rake make a solid bed for starter strip shingles, storm nailed, within two inches of the bottom of the shingle.
- The first course of shingles follows, storm nailed according to the manufacturer, and you can work your way up the rake, working into the valley.
A belt and suspenders at the eaves and edges keep sideways water out of your roof.
—Thanks to Mike Guertin for technical assistance. The 3D model in this animation is an edited version of a roof flashing model in the SketchUp Warehouse built by Ben Richardson, of HUBER. Ben also gave technical assistance.