Lay the flashing down in the roof valley and start at the lower end of the roof.
How to flash a roof valley.
Shingle the other side of the valley the same way.
Use 1 inch galvanized roofing nails.
One common method is to lay the edge metal under the eaves membrane and over the rake.
To splice the pieces add roofing cement to the lower piece and install the upper piece with at least a six inch.
Protect the eave from ice dams and sideways rain step one in steep slope roofing is the edge flashing.
Snap a chalkline 2 to 3 inches past the valley center on the top layer of shingles.
Fold the top of the flashing over the ridge.
Roof one side of the valley running the shingles across it.
Attach the flashing panel in place at the bottom.
Lay one and two tab shingles as you near the valley so full size shingles will run across the valley.
Details concrete masonry roofing wrb flashing.
Step 6 install the flashing.
Make sure that the end of the flashing panel is perfectly in line with the edge of the roof.
Now nail this first flashing at both its far ends.
Stop nailing 6 inches from the center.
Make sure to cover the gap at the bottom of the raised ridge.
Remember to caulk the underside of the flashing with a sealant.