A headwall is a junction where the top of a sloped roof meets a wall. ... Flashing should always overlap the roof-covering material. However, for aesthetic reasons, on asphalt shingle roofs, the headwall flashing flange that extends down over the shingles is often covered with a course of shingle tabs.

What is flashing for siding?

Step flashing is used where a roof and wall intersect and is placed behind the siding and underneath the roofing material. “It covers the seam where those two building elements meet,” Ojeda says. It channels water downward to the kick-out flashing, which is intended to manage water coming off step flashing.

Should flashing go under siding?

In certain instances flashing may need to be installed on the exterior of siding. However, in most instances, step flashing should be installed “behind” siding. It is always recommended to install step flashing behind stucco, Dryvit, wood panel, lap siding, vinyl siding, cedar shingle siding, etc.