There are two methods of flashing valleys in roofing systems used by roof replacement services providers: closed and open valleys. In this post, Renovation Team describes the differences between the two.
Closed Valley
Before installing shingles, the roofer installs an underlayment over the entire roof dec, such as a self-adhering ice and water shield. It can also be of a heavier gauge than the underlayment that covers the rest of the roof system. This self-adhering underlayment acts as the valley lining.
In a closed valley, the roofer installs the shingles onto the roof deck including the valley. The shingles then “close” the valley area. When finished, the self-adhering underlayment is completely covered with the asphalt shingles. The asphalt shingles become the valley lining that protects against water run-off. They also prevent water damage to your home.
Open Valley
In comparison to a closed valley, an open valley new roofing system gets another layer of lining into the valley. Experts like Renovation Team will set a pre-bent metal valley lining over the self-adhering underlayment. This lining is usually meant to withstand weather, acid rain and other such contaminants.
The asphalt shingles installed over the roof deck are set into the valley. They are not run through the valley area, though. It is also important to not nail the shingles through the valley metal. A chalk line is then drawn from the top of the valley to the bottom of the valley. The shingles crossing the line are then cut out of the valley area. This “opens” the surface of the valley lining to water run-off and the environment.
Have other roofing or even vinyl siding installation concerns? Trust Renovation Team for all your roofing needs. We also offer windows, gutters, and more to cover all your home improvement requirements. Give us a call at (314) 200-2228 or fill out our contact form for a free estimate. We serve clients in St. Louis and Chesterfield, MO.