The valley area of a roof handles a tremendous amount of water run-off. It is where two opposing surfaces of the roof system drain water that is then directed to the edge of the roof. A poorly installed valley can let water into the home, causing damage. Here are the advantages and disadvantages of closed and open roof valleys.
In a closed valley, the roofer installs the shingles extending them to “close” the valley area. When finished, the self-adhering underlayment is completely covered with the asphalt shingles. The asphalt shingles become the valley lining to protect against water run-off.
In comparison to a closed valley, a roofer adds another layer of lining into the valley at the joint. This material can consist of metal that resists weather, acid rain and contaminants. Asphalt shingles are then installed over the roof deck ,but not run through the valley area. The shingles are then cut out of the valley area where they overlap the metal. This “opens” the surface of the valley lining to water run-off and the environment.
Benefits of a Closed Valley
The most popular type of valley used by roofers is a closed valley. They are most often used due to their aesthetic qualities and fast and easy installation. They do not use extra materials, and shingles get installed across the valley. They are very cost-effective and usually installed on residential roofs.
Benefits of an Open Valley
An open valley system sheds ice and water a lot quicker. This minimizes granule loss and leads to a longer-lasting system. This type can have aesthetic appeal if well installed. It’s also easier to fix problems with an open valley system roof repair.