What Is Roof Flashing?
Flashing is a thin, waterproof metal barrier installed at roof joints and penetrations to direct water away from vulnerable areas:
Flashing is installed where the roof meets walls, chimneys, vents, skylights, dormers, valleys, and at the eaves and rakes.
Common flashing materials include aluminum, galvanized steel, copper, and stainless steel. Copper lasts the longest but is the most expensive.
Flashing creates a watertight seal at joints and penetrations where water is most likely to enter. It directs water onto the shingles and into the gutters.
Types of Roof Flashing
Different flashing types serve different purposes:
Installed in valleys (where two roof planes meet). Protects the most vulnerable area of the roof from water accumulation.
Installed along walls and chimneys. Each piece is layered like steps to direct water away from the joint.
Around plumbing vents and pipes. Rubber boots or metal collars seal the gap between the vent pipe and the roof.
At the eaves and rakes. Directs water into the gutters and protects the roof edge from water damage.
Embedded into walls and chimneys, overlapping step flashing to create a double barrier against water.
Signs of Flashing Failure
Watch for these warning signs of flashing problems:
Rusty flashing indicates the protective coating has failed. Rust creates holes where water can penetrate.
Metal flashing can crack from temperature expansion and contraction. Holes allow water to enter freely.
Wind can lift or remove flashing pieces. Missing flashing leaves joints exposed to water.
Water stains on walls or ceilings near chimneys, vents, or walls often indicate flashing failure.
Sealant around flashing can crack or shrink over time, creating gaps for water entry.
Flashing Repair and Replacement
When flashing fails, it needs to be repaired or replaced:
Small cracks or gaps can sometimes be repaired with roofing cement or sealant. This is a temporary fix at best.
Damaged flashing pieces are replaced with new metal. This requires removing shingles, replacing the flashing, and re-installing shingles.
When flashing is extensively corroded or damaged, full replacement is the most cost-effective long-term solution.
Preventing Flashing Problems
Proper maintenance helps prevent flashing failures:
Check flashing during roof inspections. Look for rust, cracks, loose pieces, and damaged sealant.
Branches rubbing against flashing can dent or scratch the metal, creating entry points for water.
Clean gutters to prevent ice dams that can lift flashing at the eaves.
Frequently Asked Questions
What is roof flashing and what does it do?
Roof flashing is thin metal installed at roof joints and penetrations to direct water away from vulnerable areas. It prevents leaks at chimneys, vents, walls, valleys, and eaves by creating a watertight barrier.
How often does flashing need to be replaced?
Flashing lasts 20-30 years with proper installation. Copper flashing can last 50+ years. Replace flashing when it shows rust, cracks, holes, or when sealant has failed. Annual inspections help catch problems early.
Can I repair flashing myself?
Minor sealant repairs can sometimes be DIY, but flashing work requires climbing on the roof and working with metal. Most flashing repairs should be done by a professional to ensure proper installation and watertight seals.
How much does flashing repair cost?
Minor flashing repairs cost $200-$600. Section replacement costs $400-$1,200. Full flashing replacement costs $800-$2,500 depending on the extent of damage and materials used.