In cold climates, where snow and ice are common, an ice-dam protection membrane is recommended on downslope roof perimeters (e.g. eaves), valleys, and around penetrations. (Consult local authorities for building code requirements.)
Dimensions shown are recommended minimums and are intended to be approximate to allow for reasonable tolerances due to field conditions. Diverter flashing should be a minimum of 26 gallon (0.019 inches) pre-finished galvanized or stainless steel, 16-ounce copper or an equivalent longevity non-corrosive sheet metal, or other appropriate material commensurate with the roofing and flashing system. Vertical flange of diverter flashing suggested to be lapped a minimum of 2 inches.