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What Are Common Roofing Flashing Types?
Ask any roofer where most leaks start and you'll hear the same answer: the flashing. These metal transitions — not the field of shingles — are the leak points. Here's what each type does and where it lives on your roof.
Why flashing matters most
A roof field is simple: overlapping shingles shed water downhill. But every place the roof meets something else — a wall, a chimney, a vent pipe, another roof plane — breaks that simple shedding, and water needs engineered direction. That's flashing's job. When flashing fails (corrosion, separation, bad installation, freeze-thaw working it loose), water gets in — even on a roof with perfect shingles.
Colorado's freeze-thaw cycling is especially hard on flashing: repeated expansion and contraction opens tiny gaps at exactly the joints flashing is meant to seal. That's why roof repair calls so often end at the flashing, not the shingles.
The common flashing types
- Step flashing: Small L-shaped pieces woven with each shingle course where the roof meets a wall. The workhorse of wall intersections.
- Counter flashing: The second layer (often set into chimney mortar joints) that overlaps the base flashing — chimneys need both.
- Valley flashing: Metal lining the valleys where two roof planes meet — the highest-water-volume zone on a pitched roof.
- Drip edge: Edge flashing directing water into gutters. See what roof drip edge is.
- Pipe boots: Rubber or metal collars sealing plumbing vent pipes. The rubber versions crack with UV age — one of the most common single leak sources.
- Chimney flashing: A system of step + counter flashing plus a cricket/saddle (a small peaked diverter) on the uphill side of wide chimneys.
- Skylight flashing: Kit-based flashing around skylights — leak-prone enough that skylight curbs deserve their own inspection attention.
How flashing fails
- Separation: Freeze-thaw and building movement open gaps at joints.
- Corrosion: Old galvanized flashing rusts through; dissimilar metals in contact corrode each other (galvanic corrosion).
- Sealant-only "flashing": Caulk smeared where metal flashing belongs — it fails within a few seasons. Real flashing is metal, shaped and layered.
- Reused flashing: Reusing old flashing during a reroof to save money — the new roof inherits the old roof's weakest link.
A quality roof installation always includes new flashing. If a quote reuses flashing, that's a quote to question.
Talk to a Colorado roofer. Suspect a flashing problem? One call connects you with an independent roofing professional who can inspect every flashing point on your roof.
What to check
From the ground with binoculars: rust streaks below flashing points, lifted or separated metal at walls and chimneys, cracked rubber pipe boots, and any place where you see caulk doing a metal's job. Inside: water stains on ceilings below chimneys, valleys, and skylights point at flashing before shingles. A professional inspection covers every flashing point systematically.
FAQs
Should flashing be replaced when I get a new roof?
Yes — always. New flashing with a new roof is standard practice; reusing old flashing is a false economy that causes early leaks.
What's the most common flashing leak?
Failed pipe boots (cracked rubber collars around vent pipes) and chimney flashing separations top the list on residential roofs.
Can I just caulk a flashing leak?
As an emergency stopgap, maybe. As a repair, no — sealant over failed flashing fails again quickly. The flashing itself needs proper repair or replacement.
Related reading
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