Roof-to-Roof Flashing

It is common to see changes in roof slope, especially where the house has an addition and the roof plane transitions from a conventional slope to a low slope. In many cases, two roof planes are covered with different styles of roof covering. For example, regular shingles on a steep slope will transition to roll roofing on a flat roof. In most cases, the material of the lower-slope roof should be extended at least 12 inches up under the covering of the conventional-slope roof. In some areas, particularly those with high snow loads, it is better if the lower-slope covering is extended as much as 3 feet up the conventional plane. Even in cases where the same roofing material is continued down both planes, there should be additional protection underneath the roof covering at the junction. At a minimum, an inspector should see an extra layer of roofing felt or an impermeable membrane.