A series of individual, L-shaped sheet metal pieces installed where a pitched roof intersects a vertical surface like a chimney, dormer or sidewall. Each piece overlaps the one below it and weaves into the shingle courses. This stepped arrangement directs water downhill and over the shingles rather than letting it run behind the siding.
Make sure you weave the step flashing properly into each course around the chimney base.
A common rookie mistake is nailing the step flashing to both the roof deck and the wall, which tears the metal when the structure settles. Nail it only to the roof deck.
Related terms
Apron flashing
A piece of sheet metal installed at the base of a wall or chimney to shed water onto the roof.
Drip edge
A metal flashing installed at roof perimeters to direct water away from the fascia and underlying wood.
Asphalt shingle
A waterproof roofing element made of a fiberglass or felt mat coated with bitumen and topped with mineral granules.