Roof flashing is thin, weather-resistant material, typically metal, installed at joints, intersections, and penetrations throughout a roof, directing water away from these vulnerable areas and preventing it from working its way beneath the roofing material into the structure below.
Because flat, uninterrupted roof surfaces shed water fairly reliably on their own, flashing specifically addresses the transitions and interruptions, valleys, chimneys, walls, and vents, where water needs deliberate guidance to keep flowing in the intended direction rather than finding its way underneath the roofing.
Different flashing types are engineered for specific locations and conditions, each addressing a particular water management challenge unique to that spot on the roof.
What Types of Roof Flashing Are There?
- Step flashing at wall and roof intersections
- Valley flashing where roof planes meet
- Chimney flashing around masonry penetrations
- Pipe and vent flashing at smaller penetrations
Why Is Roof Flashing Important?
Roofing professionals consistently identify flashing failures, rather than shingle or covering material failures, as the leading cause of roof leaks, reflecting just how much of a roof’s actual water-shedding performance depends on these often-overlooked metal components rather than the more visually prominent shingles themselves. This reality is why a thorough roof inspection focuses heavily on flashing condition at every intersection and penetration.
Flashing deteriorates through corrosion, sealant breakdown, and physical damage over time, meaning even a roof with shingles still in reasonably good condition can develop serious leaks if the underlying flashing has failed, making flashing replacement sometimes necessary well before a full roof replacement is warranted. This focus on flashing condition, rather than shingle appearance alone, often reveals the true state of a roof’s health.
Roof Flashing vs. Step Flashing
Roof flashing is the general category covering all types of water-directing metal installed throughout a roof. Step flashing is one specific type, used at the intersection between a roof slope and an adjacent vertical wall, among several distinct flashing types serving different locations.