A valley roof is formed when two portions of the roof meet at an inside angle. These valleys are common to many roofs. The Cape Cod style of architecture is one type of home that is traditionally free of valleys if there are no dormer windows on the roof. Many times, valleys are created where the roof on the main part of the house meets the garage roof or when an addition is put on the original roof.
A valley roof leak is the most common type of roof leak. These leaks can be caused by poor roofing practices or just simply by the age of the shingles on the roof. A roofer must be careful where the nails are placed in the shingles of valley roofs. If the nails are placed in the very center of the valley, leakage will occur. If the nails are placed closer than 6 inches (15.2 cm) from the center of the valley, tension could be placed on the shingle, causing it to torque. Within a few short years, this tension could cause the shingle to rip, which will then expose the bare roof to the elements.
A metal valley roof helps eliminate those issues because the metal cannot rip or torque. Another benefit of metal roofs is that they have a life span of at least 50 years. This is much longer than asphalt shingles' average life span of about 20 years.
Roof valley shingles can be the same type of shingles that are used on the rest of the house. Roofers employ a few techniques that allow them to use the same shingles on the whole roof instead of purchasing specialty shingles. These techniques are variations of a herringbone pattern, and they create a very effective water barrier. One tool in the roofer's arsenal is called valley roof flashing. This metal flashing is an effective and impenetrable barrier that is laid underneath the shingles as insurance against worn shingles.
A valley roof can collect leaves and other debris. As the debris gathers in this vulnerable area, water no longer flows freely into the gutters. In the winter season, ice collects in this area, and as the ice freezes and thaws, the shingles get pushed around, causing them to move and wear. In addition to employing roofers who use proper roofing techniques, the homeowner should check the roof and gutters at least twice every year and clean out any debris that is clogging them.