A method for weatherproofing the intersection of two sloping roof planes. Roofers run the shingles from the lower-slope or larger roof area completely across the valley. They then install the shingles from the intersecting roof over the top and cut them in a straight line about two inches back from the centerline. This creates a clean, straight visual line while maintaining a continuous water barrier underneath without needing exposed metal flashing.
Make sure you run the main deck shingles fully through the closed-cut valley before you snap the chalk line for the dormer side.
Always cut the top layer of shingles carefully to avoid slicing into the underlying shingles that cross the valley.
Do not mix it up with
- Open valley: A closed-cut valley covers the intersection entirely with shingles, whereas an open valley leaves a central strip of metal flashing exposed.
Related terms
Open valley
A roof valley where the shingles are cut back to expose a continuous metal flashing down the center.
Asphalt shingle
A waterproof roofing element made of a fiberglass or felt mat coated with bitumen and topped with mineral granules.
Roof assembly
The complete system of interacting components that form a building's roof, from the structural deck up to the weatherproofing layer.