Roof Valley Flashing Details

Valleys: Certi-label^TM Shingles

For roofs with slopes of 12:12 or greater, valley flashing should extend not less than 8" on each side of the valley centerline. For roof slopes less than 12:12, flashing should extend not less than 11" each side. Valley flashing should be center-crimped, painted, galvanized steel or aluminum. Valley metal should be underlayed with minimum Type 30 ASTM Designation 226 (ASTM D226) or ASTM Designation 4869 (ASTM D 4869) roofing felt. Shingles should not be applied with their grain parallel to the valley centerline and those extending into the valley should be cut at the correct angle (Figure 13b). 

Valleys: Certi-label^TM Shakes

On shake roofs it is recommended that a strip of Type 30 ASTM Designation 226 (ASTM D226) or ASTM Designation 4869 (ASTM D 4869) roofing felt be installed over the sheathing and under the metal valley. Metal valleys should be center-crimped, painted, galvanized steel or aluminum and should extend not less than 11" on each side of the valley centerline. In some areas, however, flashing width requirements may differ and local building codes should be consulted. Shakes should not be applied with their grain parallel to the valley centerline and those extending into the valley should be cut at the correct angle (Figure 13c).