Correct construction of roof junctures and slope transitions is vital to ensure the integrity of the roof system. In the following cases, where metal flashing is employed, it should be no less than 26 gauge galvanized steel or acceptable equivalent. Check with your local building official for their preference in your area. It should be painted on both sides with a good metal or bituminous paint. Flashing materials should be painted after bending to maintain the integrity of the coating.
On this type of juncture (Figure 9) metal flashings should be installed to cover the top 4" of the wall and the bottom 8" of the roof slope before the final course of Certi-labelTM shakes or shingles is nailed to the top of the wall. A strip of wood molding can be applied after the final wall course is installed. A double or triple starter course is then applied at the eave, with a 1 1/2" overhang over the outside wall trim. The roof can then be completed in the normal manner.
Metal flashings for the concave juncture are similar to those for the convex type. They should be installed to cover the top of the roof slope and the bottom 4" of the wall before the final course of Certi-labelTM shakes or shingles is installed. The final roof course should be installed so that the tips fit as snugly as possible against the wall at the juncture. A double starter course should be applied at the start of the wall surface and the remaining wall courses applied in the recommended manner. If nails are not acceptable through exposed metal, metal clips can be used to hold down the flashing.
Roof transitions (Figure 10) require appropriate flashing, felt and product application. Changes in roof slope should be detailed in a similar manner to concave junctures, to ensure the integrity of the roof system. Solid sheathing is required above and below the change in slope, metal flashing is required across the change in slope, and a 36" strip of starter felt is required on the upper slope, installed in the same fashion as at the eaves.