Know Your Roof · Flashing & Roof Edge
Apron Flashing: Where a Roof Runs Into a Wall
Quick answer
Apron flashing is a long piece of bent metal that seals the joint where a roof slope runs up into a vertical surface, like the front of a chimney, a dormer face or a wall at the top of a slope. It sheds water running down that wall onto the roof, and counter flashing or siding covers its top edge.
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Where apron flashing goes
The downslope face of a chimney. The front of a dormer. A headwall, where a lower roof meets a taller wall. Walls at the top of a low-slope or flat roof section.
How it differs from step flashing
Step flashing is a series of small pieces along sloped joints. Apron flashing is one piece along a level joint, the horizontal line where the roof ends against a wall.
How it works
The lower edge lies over the shingles. The upper edge runs up the wall and is covered by counter flashing, siding or house wrap. Water running down the wall lands on the apron and flows out over the shingles.
Common problems
Sealant used instead of overlap. Lifted or bent metal. Rust. And flashing that was never tied into the siding or counter flashing.
What does apron flashing repair cost?
Apron flashing at the base of a chimney or wall is a small, targeted repair when caught early. Flashing repair around a wall, chimney, or valley typically runs $400 to $900. A minor repair that includes flashing, a vent boot, or one or two shingles runs $400 to $750. The final number depends on how much flashing is damaged and how hard it is to reach, and every job starts with a free roof inspection.
Looking for another word? See the roofing terms glossary, A to Z.