Roof flashing

Flashing is sheet metal (typically aluminum, copper, or galvanized steel) installed at roof transitions, penetrations, and edges to direct water away from vulnerable joints. Common flashing locations: chimney perimeters, vent pipes, skylights, valley junctions, sidewalls (where roof meets a vertical wall), eaves and rakes, dormers.

When flashing is properly installed, water flows over the metal surfaces and away from the joint. When it's poorly installed (or missing entirely), water infiltrates the joint and migrates into the structure. The vast majority of roof leaks originate at flashing failures, not at field shingles.

For roofing operators, flashing quality is the difference between a roof that lasts 25+ years and one that develops leaks within 5-10 years. Common shortcuts that create future problems: re-using existing flashing during a tear-off (flashing should be replaced when shingles are replaced), inadequate step flashing at sidewalls (should overlap each shingle course, not span multiple courses), insufficient flashing dimensions at chimney/vent perimeters. Customer-facing positioning around flashing quality is a meaningful differentiator from low-bid competitors who skip the flashing investment.