Flashing Most roof leaks can occur where water is channeled off the roof or where the roof abuts a vertical wall or chimney. At these points, metal valleys and flashings are used to assist the Certi-label shakes and shingles in keeping the structure sound and dry. Structural members that join a roof should also be flashed at all intersecting angles to prevent leakage. Flashing strips which must be bent to sharp angles should be painted after bending.
Metal flashing with baked-on enamel coating is available in some areas.
Different flashing metals are available in different areas depending on climatic variations. It is good practice to use metals that have proven their reliability under the specific conditions to be encountered. It is important that metal flashing have the same longevity as Western Red Cedar. Check with your local building official for their preference in your area. Valley flashing should be center-crimped, painted, galvanized steel or aluminum.