Common Symptoms
- ✓Water stain near chimney, skylight, or exterior wall where roof meets siding
- ✓Visible rust streaks or lifted metal strips at roof edges or chimney base
- ✓Caulk pulling away or cracking at any roof penetration
- ✓Recurring leak in the same location after previous repairs
- ✓Deteriorated mortar between chimney and flashing counter-flashing
- ✓Dark staining or moss growth concentrated at a valley or transition
What Causes This
Flashing is the leading cause of chronic, recurring roof leaks in St. Louis homes, particularly those over 12 years old. Thermal expansion and contraction in Missouri's climate — sub-zero January lows and 100-degree July highs — work metal and sealant joints through thousands of cycles per year. Galvanized steel flashing corrodes, aluminum work-hardens and cracks, and the rubberized sealant used to seal step flashing legs dries and shrinks. Valley flashing in homes built before the 2000s was often installed with open metal valleys rather than closed woven valleys, and the exposed metal corrodes through entirely. Chimney counter-flashing set in masonry mortar joints is particularly vulnerable as the mortar weathers.
When to Call Immediately
Re-caulking over failed flashing is a temporary measure, not a repair. If a previous contractor applied caulk over existing flashing more than once, the flashing likely needs full replacement. Caulk bonds fail in two to three years under St. Louis thermal cycling — metal replacement holds for 20+ years.
How Revolve Fixes It
- 1Inspect all flashing types present — chimney, step, valley, drip edge, kickout, and any skylights or pipes — and document condition.
- 2Remove deteriorated sealant and test for metal integrity; corroded-through or kinked flashing requires full replacement, not re-caulking.
- 3Install new flashing using the appropriate material — galvanized or stainless step flashing at sidewalls, lead or aluminum at chimney, EPDM or neoprene boots at pipes.
- 4Seal all laps and terminations with roofing-grade polyurethane or butyl sealant rated for metal-to-shingle applications.
- 5Re-bed any masonry counter-flashing in fresh mortar where applicable; re-tuck lead flashing into reglets.
- 6Perform a water test with a garden hose before closing out the job to verify all repair points are watertight.
Types of Flashing and Where Each Fails
Step flashing is the L-shaped metal woven between each course of shingles where the roof meets a sidewall or dormer. Each individual piece is small, so failure is gradual — one or two pieces lift, water gets behind the shingles, and by the time you notice the interior stain, several feet of step flashing have been compromised. This is the most common flashing repair we perform in St. Louis.
Chimney flashing consists of two components: base flashing that laps onto the roof surface, and counter-flashing that is set into the masonry and overlaps the base flashing. Both must be intact. Counter-flashing mortar joints in older St. Louis brick homes crack and crumble, allowing water to funnel directly behind the base flashing and into the attic.
Valley flashing covers the intersection where two roof planes meet. Open metal valleys rust through. Closed woven valleys and closed-cut valleys using underlayment eventually develop shingle granule erosion at the high-traffic water channel, and the exposed shingle degrades faster than the field. Both conditions are repairable without replacing the full roof.
Why Flashing Repairs Require Partial Shingle Removal
Proper step flashing replacement requires lifting the shingles that overlap each flashing leg. There is no way to slide new step flashing in from the side without disturbing the shingle above. Any contractor who claims to repair step flashing by caulking from the exterior without removing shingles is applying a temporary patch, not a repair.
This is the reason flashing repair costs more than homeowners expect. The labor involves careful shingle removal, flashing replacement, and reinstallation of shingles in the correct offset and nail pattern. When we lift shingles for flashing work, we also inspect the underlayment beneath — if the felt or synthetic underlayment has deteriorated in the same zone, we replace it as part of the same repair.
Material selection matters. Galvanized steel step flashing is the standard for most applications and holds up well when installed correctly. Aluminum is lighter and easier to form but work-hardens over time and can crack at bends. For chimney applications where mortar contact is involved, lead or lead-coated copper is the most durable long-term choice and is what we specify on older masonry chimneys.
Flashing and Manufacturer Warranties
Most asphalt shingle manufacturer warranties — GAF, Owens Corning, CertainTeed — require that flashings be installed per their specifications to keep the warranty valid. Improper flashing installation or the use of sealant-only repairs in lieu of proper metal flashing can void the warranty on the surrounding shingles. This is a real exposure for homeowners who have relatively new roofs with flashing failures.
Revolve carries certifications from all three major manufacturers: GAF Certified Contractor, OC Preferred Contractor, and CertainTeed Select ShingleMaster. When we perform a flashing repair on a roof under an active manufacturer warranty, we document the repair in a way that supports rather than jeopardizes the warranty coverage.
If your roof was installed within the last 10 years and the flashing is already failing, that is a workmanship issue that may be covered under the original installer's warranty or under the manufacturer's system warranty. We will tell you if that is likely the case before you pay for a repair that someone else may owe you.
Frequently Asked Questions
How long does roof flashing last?+
Properly installed galvanized steel flashing lasts 15–25 years in St. Louis conditions. Aluminum flashing can last 20+ years but is more prone to cracking at bends. Lead and copper flashing can last 50 years or more. Sealant-only applications without metal flashing typically last 2–4 years before requiring re-application.
Can flashing be repaired without replacing shingles?+
Only in limited cases — where the flashing itself is intact but the sealant has failed, careful re-caulking without shingle disturbance can extend service life by a few years. Any repair involving the flashing metal itself requires lifting the overlapping shingles. We always preserve existing shingles where possible during flashing work.
My chimney flashing was re-caulked twice and still leaks. What's the real fix?+
If caulk has been applied over the same joint more than once, the underlying metal is almost certainly corroded, lifted, or improperly bedded. The caulk is bridging a gap that the metal should be covering. The correct fix is full counter-flashing and base flashing replacement — typically $700–$1,200 for a standard single-flue chimney.
Does homeowners insurance cover flashing failure?+
Insurance covers sudden storm damage, not gradual deterioration. A wind event that lifts or tears flashing can be a covered claim. Age-related corrosion and sealant failure is a maintenance issue and is generally not covered. We photograph all conditions during inspection so you have documentation if a storm component exists.
How much does it cost to replace all flashing on a house?+
Full flashing replacement on a typical 2,000–2,500 sq ft St. Louis home during a re-roof runs $800–$2,500 depending on the number of penetrations, valleys, and chimneys. As a standalone repair on an existing roof, per-zone pricing applies: chimney $700–$1,200, step flashing per run $300–$600, valley $400–$800.