Last updated: 2026-08-24 by Ted Sellers, Owner
Most roof-flashing repairs require replacing or correctly resetting the damaged metal—not simply covering the area with caulk. The right repair depends on where the leak is coming from: a chimney, sidewall, vent, skylight, valley, or another roof transition.
Flashing is the metal that directs water away from the places where a roof changes direction or meets another surface. When it is loose, rusted, punctured, installed in the wrong order, or sealed over repeatedly, water can reach the underlayment and roof deck. If you are tracing an active leak, start by identifying where the water is actually entering; the wet spot inside is often not directly below the failure.
How do you fix roof flashing?
Repairing roof flashing starts with identifying the failed detail, removing only the materials necessary to reach it, and installing new flashing so water sheds over—not behind—the next layer. Sealant can support the detail, but it should not be used as a substitute for properly lapped flashing or damaged shingles.
For steep-slope shingle roofs, step flashing is normally woven into the shingle courses where a roof meets a wall or chimney. GAF’s technical guidance explains why correct step and counterflashing matter at these transitions. Review the manufacturer’s Proper Flashing bulletin and the applicable Minnesota Residential Code flashing requirements before planning a major repair.
Common flashing problems and the usual repair
| What you see | What may be wrong | Typical next step |
|---|---|---|
| Water marks near a chimney or wall | Step flashing, counterflashing, or sealant has failed | Inspect the flashing layers; replace damaged sections instead of only surface-sealing them. |
| Loose pipe boot or cracked collar | Penetration flashing has aged or split | Replace the boot or flashing assembly and check the adjacent shingles. |
| Rust, holes, or lifted metal | Corrosion, storm damage, or failed fasteners | Remove and replace the affected flashing with compatible, corrosion-resistant material. |
| Leak after a prior patch | Water is getting behind the patch or the source is elsewhere | Trace the water path before adding more sealant; a hidden shingle or counterflashing failure may be involved. |
When sealant is enough—and when it is not
Sealant may help with a small, accessible gap after the underlying flashing is still sound and correctly installed. It is not a dependable long-term fix for rusted metal, missing step flashing, open laps, a split pipe boot, or water that is already getting beneath shingles.
Think of sealant as a finishing material, not the whole waterproofing system. If you can see multiple layers of old tar or caulk, repeated patching is often hiding the actual problem.
Step-by-step: how a flashing repair is approached
- Find the water path. Check the roof penetration or transition above the leak, then inspect the attic or ceiling area for staining and damp insulation.
- Identify the flashing type. Chimneys, walls, valleys, skylights, vents, and plumbing stacks each use different details. The repair method should match the roof system.
- Protect the roof and yourself. Roof work can involve steep slopes, brittle shingles, and fall hazards. Use appropriate fall protection and avoid working on wet, icy, or unstable roofing.
- Remove damaged material carefully. Lift only the shingles and fasteners necessary to expose the failed flashing. Do not tear the surrounding underlayment or force a repair over soft or rotted decking.
- Install the new flashing in the water-shedding order. Each layer should direct water onto the layer below it. On shingle roofs, step flashing is integrated with the shingle courses rather than nailed or caulked on top.
- Repair the roofing around it. Replace damaged shingles, confirm exposed fasteners are handled correctly, and follow the product instructions for any sealant used.
- Test thoughtfully. After the repair is complete and materials have cured as directed, test from the lower portion of the detail upward. Stop if water appears inside and reassess the source.
When to call a roofing professional
Call a roofer when the leak is active, the repair involves a chimney or steep roof, shingles need to be removed, or you cannot safely identify the failed detail. Those conditions usually require more than a tube of sealant.
Sellers Roofing can help homeowners and property managers assess leaking flashing and roof transitions in the Twin Cities. If you need a professional evaluation, visit our St. Paul roof repair page or request a roofing estimate with our team.
Frequently asked questions about roof flashing
What is roof flashing?
Roof flashing is a thin, durable material used to direct water away from joints and roof transitions. It is commonly installed around chimneys, walls, skylights, valleys, and plumbing vents.
Can I repair roof flashing with caulk alone?
Usually, no. Caulk can seal a minor gap on sound flashing, but it will not correct corroded metal, missing flashing, improper overlap, or water trapped beneath shingles.
How often should roof flashing be inspected?
Inspect flashing during routine roof checks and after major wind or hail events. Look for loose metal, cracked sealant, rust, missing fasteners, or new interior water stains.
Does flashing need to be replaced when a roof is replaced?
It depends on the flashing type and condition, but replacement is often the safer choice when existing flashing is corroded, undersized, damaged, or incompatible with the new roof system. Follow the manufacturer’s installation instructions and the applicable code requirements for the project.
Sources and next step
If your roof is leaking or you are unsure whether a flashing patch is enough, get in touch with Sellers Roofing for a written roof-repair assessment.
Need a roof inspection in Saint Paul or the Twin Cities? Call Sellers Roofing Company at +1-651-703-2336 or schedule a free estimate. We are a black-owned, NMSDC-certified MBE roofing contractor with 9+ years experience.
