Is the overlap of the bottom three inches of a slate over the top three inches of the slate in the second row below the first slate, or the top three inches of any slate.
Shortest distance from the butt edge of an overlapping shingle to the upper edge of a shingle in the second course below. The triple coverage portion of the top lap of strip shingles.
In a bituminous assembly, the overlap between the lower edge of the top exposed ply and the upper edge of the bottom ply, which provides a margin which ensures that the membrane is actually a two, three, or four ply membrane.
The overlapping of shingles or roofing felt at their top edge. Roofing felt should be headlapped by a minimum of 2 in. French (Recouvrement supérieur)
the minimum distance allowable from the upper edge of a shingle or felt
The distance that the topmost ply of roofing felt overlaps the undermost ply or course.
the distance of overlap measured from the uppermost ply or course to the point that it laps over the undermost ply or course.
the minimum distance, measured at 90 degrees to the eaves along the face of a shingle or felt, from the upper edge of the shingle or felt to the nearest exposed surface.