Roof flashing is a thin metal barrier that seals joints and transitions where water is most likely to penetrate. Coastal Windows & Exteriors is a GAF Master Elite contractor and woman-owned exterior remodeling company with 7,000+ installations completed since 2011, serving 730+ towns across Massachusetts, New Hampshire and Maine with roofing systems built to seal out water at every critical transition.
It’s one of the most critical, and most overlooked, components of any roofing system.
What Flashing Does and Where It Lives
- Flashing Seals the Vulnerable Points: Every place your roof changes direction or meets a wall, chimney, skylight, or vent is a potential leak entry point. Flashing covers these transitions and channels water away from the structure.
- Where You’ll Find It: Common flashing locations include chimney bases, roof valleys, skylights, vent pipes, and side walls. Each requires precise installation to perform correctly.
- Poorly Installed Flashing Is a Top Cause of Leaks: Many roof leaks originate at flashing joints, not at the shingles themselves. This is true on older Colonial and Tudor-style homes with complex rooflines.
- Flashing Materials Matter: Quality flashing uses durable metals that resist corrosion and expand and contract with temperature changes. Temperature swings make this critical.
- Flashing Works With the Full System: Our GAF 6-layer approach treats flashing as part of a complete waterproofing strategy, not an afterthought. Leak Barrier Protection and Roof Deck Protection work alongside flashing for complete coverage.
- Inspect After Every Major Storm: Flashing can lift, crack, or separate over time. A post-storm inspection catches flashing issues early, before water reaches your interior ceiling.
- A Top Roofing Service Includes Flashing Assessment: Every top roofing service we complete includes a full review of existing flashing conditions before installation begins.
Flashing Recommendations for Homeowners
- Top Recommendation: Have flashing inspected any time your roof is over 15 years old or after a major storm, especially on homes with dormers or chimneys.
- Best for Older Homes: Full flashing replacement paired with a complete roof replacement for a fully integrated waterproofing system.
- Best for Peace of Mind: Schedule a free inspection with our certified team to assess your roof’s current flashing condition.
Concerned about your roof’s flashing? Reach out to Coastal Windows & Exteriors for a free evaluation today.
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Still have questions about What Is Flashing on a Roof, and Why Does It Matter? See the areas we serve and talk to your local roofing contractor.
Last Updated: July 2026
Sources:
- Asphalt shingles cost $4.46 per square foot on average nationally. This Old House Roofing Facts and Statistics, roofing material cost data and industry statistics for homeowners. (2025)
