Open Valley Roof Vs Closed

After the self adhering underlayment is installed across the valley a pre bent metal valley lining is installed.

Open valley roof vs closed.

Proponents of the open version say that an open flashing allows the rainwater to move away from the roof faster. Repairs to closed valleys are a lot more involved than working on an open valley as is re roofing or making changes to a portion of your roof in the future. I further feel that an open metal valley would flush faster without wearing away the granules. In comparison to a closed valley an open valley adds another layer of lining into the valley.

Closed valleys are very vulnerable to mechanical damage. Since it isn t bogged down by the friction shingles invariably create. This leaves a metal strip or line on the surface of the roof that serves as the valley line. Open roof valley this is almost the same as the closed roof valley method except a pre bent metal valley lining is installed instead of a secondary roof underlayment.

The closed variation is a flashing that has been completely covered with shingles while in the open variation will have the flashing completely exposed to the elements. The only type of valley that is unacceptable is the woven valley. After the underlayment is placed a pre bent metal valley lining is installed. The metal is usually pre painted to best complement the shingles color blend.

Regardless of open or closed this of course presumes that a grace water ice membrane is used. Although the open valley is recommended by the manufacturer closed valley is acceptable. An open valley has a gap usually about 6 inches between the tile or shingles at the valley area. Once the shingles are installed they don t run through the valley area.

Open valley when compared to a closed valley and open valley adds an additional layer of lining. A closed valley is where the tiles or shingles are butted up against each other in the center of the valley. This metal lining can be made of any type of metal that is resistant to the effects of weather acid rain or other contaminants. It is always a good idea to check with the manufacturer or a certified installer of the product such as ourselves.

And while some homeowners may prefer the aesthetics of a closed valley the heavier and thicker the shingle the less likely it is to lie flat across a joint. In looking at the fabral metal roofing supply catalog it has a valley flashing that from the end looks like a w.