Most Roof Leaks Aren't From the Shingles
If your roof is leaking and you can’t find an obvious broken shingle, there’s a good chance the problem is in the flashing. Flashing is the metal that seals every joint, intersection, and penetration on your roof, and it’s responsible for the majority of leaks we find in Calgary and Edmonton homes. Here’s what it is, where it fails, and how it gets fixed properly.
Signs Your Flashing Has Failed
Flashing failures are tricky because the water entry point is almost never directly above where the stain appears inside. Here's what points to a flashing problem rather than a shingle problem.
Leaking Near a Chimney, Skylight, or Vent
If water is entering your home near any roof penetration, your first suspect should always be the flashing around it, not the penetration itself. Chimneys, skylights, plumbing vents, and HVAC curbs all require flashing, and it’s the flashing joints that fail first, typically long before the shingles surrounding them.
Leaking in a Valley
A valley is where two roof planes meet. Water from both planes flows toward this intersection, making it the highest-volume drainage point on the roof. Leaks in valleys are almost always caused by failed valley flashing or improperly lapped valley underlayment, not by the shingles themselves.
Staining on the Wall Where a Roof Meets a Sidewall
Where a sloped roof butts against a vertical wall (a common configuration on additions, dormers, and attached garages), the transition is sealed by step flashing and counter flashing. When this fails, water tracks down the wall cavity and often shows up as staining on interior walls or at the base of the wall well below the actual leak source.
Water Stains Along the Eaves After Rain
Drip edge is the metal flashing that runs along the eave and rake edges of the roof, directing water into the eavestrough rather than behind the fascia. When drip edge is missing, corroded, or improperly installed, water runs behind the fascia board and rots it from the back, often showing up as staining or soft spots along the roofline before any interior leak appears.
Visible Rust Streaks on Shingles or Walls
Orange or brown rust streaks running down the shingle surface from a chimney, vent cap, or pipe boot indicate that the metal component is corroding. Corroded metal is also cracking and pulling away from the sealant joints around it, meaning water intrusion is either already happening or very close.
Old Tar or Caulk Patches Visible on the Roof
If you can see black tar or dried caulk smeared around penetrations or joints on your roof, a previous contractor applied a temporary patch rather than a proper repair. These patches typically last one to three Alberta winters before cracking, and by the time you’re looking at them they may have already failed. Tar over failed flashing is a delay, not a fix.
What Flashing Is, Where It Lives, and Why It Fails
Flashing is the system of metal components (typically aluminum, galvanized steel, or copper) that seals every point where the roof surface meets something that interrupts it. Shingles are excellent at shedding water on an uninterrupted slope. But every chimney, vent, valley, and wall intersection creates a joint that shingles alone can’t waterproof. That’s what flashing does.
Flashing fails for several reasons. Thermal movement is the biggest one in Alberta: metal expands in summer heat and contracts in winter cold, and over 40 or more freeze-thaw cycles per year, the sealant that bonds flashing to masonry, frames, or adjacent metal fatigues and cracks. Once the sealant fails, even a small gap allows wind-driven water or pooled meltwater to enter behind the flashing and into the roof system.
Poor installation is the second major cause. Flashing that’s been nailed through instead of slipped under shingles, step flashing that doesn’t overlap properly, or counter flashing that’s just caulked instead of embedded in mortar joints, these shortcuts create failure points that typically show up within three to five years. Reusing old flashing during a shingle replacement is one of the most common ways a brand-new roof develops a leak in year two.
WHY LEAKS APPEAR FAR FROM WHERE FLASHING FAILS
Water that enters through a failed flashing seam doesn't drip straight down. It follows the path of least resistance, travelling along rafters, underlayment, and decking before finally dropping somewhere visible. A chimney flashing failure on the back of the chimney can produce a ceiling stain three metres away from the chimney itself. This is why finding the actual source of a roof leak almost always requires getting on the roof and into the attic, not just looking at where the stain appears inside.
WHAT EACH ONE DOES AND WHY IT FAILS
Chimney Flashing
A chimney is the most demanding flashing job on any roof. The chimney and the roof structure expand and contract at different rates, constantly stressing the metal and sealant joints. Saddle (cricket) flashings behind the chimney prevent water pooling. Counter flashing embedded in the mortar provides the upper seal. Both fail over time in Alberta’s freeze-thaw climate.
Valley Flashing
Valleys carry the highest volume of water on the roof. Open metal valleys are the most durable but require precise installation. Closed-cut and woven valleys rely on shingles for waterproofing and fail faster in high-volume drainage zones. Failed valley flashing is often mistaken for a shingle problem because the leak appears along the valley where shingles are visible.
Drip Edge
Drip edge is the L-shaped metal strip installed at every roof edge. It directs water cleanly into the eavestrough and prevents water from wicking back under the shingles via capillary action. Many older roofs in Calgary are missing drip edge entirely. Advanced Level Roofing installs drip edge on every replacement as standard, not as an optional upgrade.
Pipe Boots
Pipe boots are the rubber and metal collars that seal plumbing vent stacks where they exit through the roof. The rubber gasket degrades under UV exposure and freeze-thaw cycling, typically cracking within 10 to 15 years. A failed pipe boot is one of the most common sources of small, persistent drips that homeowners can’t trace.
Step and Wall Flashing
Where a sloped roof meets a vertical wall (dormers, additions, skylights), step flashing (small L-shaped pieces integrated with each shingle course) and counter flashing (the upper seal against the wall) work together. When counter flashing pulls away from the wall or step flashing is improperly overlapped, water enters the wall cavity, often appearing as interior staining well below the actual roof junction.
What Happens When Flashing Failure Goes Unaddressed
Flashing leaks are slow and deceptive. The water entry is small, often invisible from the interior until significant damage has already accumulated. Here’s what’s building up while you wait.
Decking and Rafter Rot
Water entering through failed flashing doesn’t announce itself with a dramatic drip. It soaks slowly into the decking and adjacent rafter tails over months and seasons. Wood that’s repeatedly wet and dry loses structural integrity quietly. By the time you see evidence of it inside, the wood it’s been soaking has often already begun to degrade.
Hidden Mould in Wall Cavities
Water that enters through wall- junction or chimney flashing typically travels inside the wall cavity before it appears anywhere visible. Mould can establish in a wall cavity within 24 to 72 hours given the right moisture conditions, and because the cavity is enclosed, it can grow unchecked for months or years. Remediation of wall cavity mould is significantly more expensive than a flashing repair.
New Roof, Same Leak
The most expensive consequence of ignored flashing failure is a roof replacement that doesn’t solve the problem. If flashing is the source of the leak and only shingles are replaced, the new roof leaks in the same spot within a season or two. We see this regularly when homeowners hire contractors who reuse old flashing during replacement. A new roof should always include new flashing.
What to Do Right Now
If you suspect a flashing problem, here's the right sequence before the next rain event hits.
01.Map the Leak Pattern to Narrow Down the Location
Note where and when the leak appears inside. Does it only happen during heavy rain, or also during light rain? Does it show up during snowmelt but not rain? Is the stain near a chimney, an exterior wall, a valley, or an interior location that doesn't correspond to any obvious penetration? This information significantly narrows down which flashing zone is the likely source before anyone gets on the roof.
02.Check the Attic for the Entry Point
On a dry day, access your attic with a flashlight. Look at the underside of the decking around penetrations (chimneys, pipe stacks, skylights) and along the valley lines. Water staining on the underside of the decking, wet insulation, or rust on nail tips often traces back toward the actual leak source more reliably than the ceiling stain below. Photograph what you find.
03.Don't Apply Tar or Caulk
Roofing tar and caulk applied over failed flashing seal the surface but not the failure. They typically hold for one season before UV degradation and thermal movement crack them again. Worse, tar applied over a flashing joint makes the proper repair more difficult by contaminating the metal and surrounding shingles. If you need to buy time before the next rain, a professional temporary tarping over the affected area is more effective and less likely to complicate the eventual fix.
04.Request a Flashing-Specific Inspection
A proper flashing inspection requires getting onto the roof and physically examining each flashing zone: checking sealant condition, testing whether metal has pulled away from adjacent surfaces, looking for corrosion at lap joints, and checking that step flashing is correctly integrated with each shingle course. This isn't a job for a ground-level visual assessment or a drone alone.
ON REUSING OLD FLASHING DURING A ROOF REPLACEMENT
Some contractors offer to save money by reusing existing flashing when replacing shingles. This is one of the most common sources of post-replacement leaks. Old flashing metal may be corroded or deformed, the sealant at existing joints is already fatigued, and reinstalling old flashing correctly around new shingles is actually more labour-intensive than installing new. Advanced Level Roofing installs new flashing on every complete roof replacement. It's not optional because we're the ones standing behind a 5-year workmanship warranty.
How Advanced Level Roofing Finds and Fixes Flashing Failures
Finding the actual source of a flashing leak requires methodology, not guesswork. Our process traces the water entry point from the evidence it leaves rather than just looking where the ceiling stain appears.
Multi-Point Flashing Audit: Roof and Attic
We inspect every flashing zone on the roof (chimney, valleys, drip edges, all penetrations, and wall junctions) and correlate the findings with the interior evidence from the attic. We document every failure point with high-resolution photography so you can see exactly what we're seeing and why we're recommending the repair scope we are.
Proper Flashing Repair: Metal Replaced, Not Patched
We remove the surrounding shingles to expose the failing flashing, strip out the old metal, and install new flashing components correctly. For chimney flashing, that means new step flashing, new saddle flashing, and properly embedded counter flashing. For valleys, new metal flashing integrated correctly with the underlayment. For pipe boots, new rubber and metal collar units. Caulk is used to finish joints, not to substitute for proper metal installation.
Ice-and-Water Shield at All Critical Zones
At every flashing repair zone, we install new ice-and-water shield membrane before the new flashing and shingles go on. This self- adhering membrane seals around nails and provides a secondary waterproofing layer at exactly the points where flashing failure is most destructive. In Alberta's climate, this isn't optional at chimney bases, valleys, or eave areas.
Written Warranty on All Flashing Work
All flashing repairs we perform are covered under our 5-year workmanship warranty alongside the IKO Limited Lifetime Warranty on materials. We provide documentation of what was replaced, the materials used, and photographic before-and-after evidence of the repair for your records.
DAVID R. , Tuscany, NW Calgary
Our roof was 17 years old and we'd been quoted $18,000 for a replacement. Advanced Level Roofing assessed it and said the decking was sound and the shingles had good life left — they recommended the life extension treatment instead. We paid a fraction of the replacement quote, and two years later the roof is performing exactly as they said it would. They could have sold us a replacement and they chose not to — that kind of honesty is rare.
Yannick Rouette , Calgary
Advanced Level Roofing replaced the roof on my house in April 2025. The previous roof was damaged by hail and I paid for Class 4 hail-resistant shingles. They delivered the shingles on a Thursday and came for the removal and installation on Saturday. They did all the work in a single day, from 8 am to 4:30 pm. The employees were nice and careful. They cleaned everything around the house and passed their rolling magnet over my yard ten times to remove all nails. They sent me a photo inspection of the roof. I would recommend this company. Their prices are great.
JOHN D. , Calgary
Yesterday I had my roof replaced by a team from Advanced Level Roofing. True professionals who know what they do. I saw them working on houses around me for two years now and their jobs look awesome. You can see other companies dragging a roof job on for days, but these guys try their best to do it in one day and that was the case for me. The whole process from estimate to installation was a breeze. The price was fair and the estimator answered all my questions. When dusk set in, they were gone and everything was clean and nice around the house. The roof looks awesome. As much as I like what you've done, I don't want to see you again for the next 20 years or so!
What Does Flashing Repair Cost, and Is It Covered?
Flashing repair costs depend on which flashing zone has failed and how much surrounding shingle work is required. A single pipe boot replacement typically runs $200 to $500. Chimney flashing repair or rebuild (the most complex flashing job) typically runs $800 to $2,500 depending on chimney size and the extent of counter flashing work required.
Valley flashing repair ranges from $600 to $1,800 depending on valley length and the shingle scope required. Full drip edge installation on a home without it runs $400 to $900. When multiple flashing zones need attention at the same time, we provide a consolidated quote that’s more cost- effective than treating each as a separate visit.
On insurance: flashing damage caused by a covered weather event (hail denting the metal, wind tearing flashing from the wall, or an ice dam forcing flashing apart) can be a valid insurance claim, and we help document these cases for adjusters. Flashing that has failed through age, UV degradation, or thermal movement over time is typically classified as a maintenance issue. We’ll tell you honestly which category your situation falls into during the inspection.
Dealing With a Related Problem?
Flashing failures rarely exist in isolation. These are the problems most commonly connected to what you're experiencing.
Emergency Roof Repair
If a flashing failure is causing an active interior leak right now, this guide covers what to do in the next 30 minutes to protect your home while you arrange a proper repair.
Skylight Leak Repair
Skylight leaks are almost always a flashing problem. If your leak is near a skylight specifically, this guide covers the step and counter flashing components unique to that repair.
Roof Insurance Claims
If the flashing failure was triggered by a storm event, this guide walks you through the Alberta insurance claims process and how we assist with documentation and adjuster representation.
Flashing Repairs Across Calgary and Western Canada
We carry out flashing repairs across all our markets. Given the freeze-thaw and hail exposure in Alberta, flashing maintenance is one of the most impactful things a homeowner can stay on top of in Calgary and Edmonton.
Frequently Asked Questions
How do I know if it’s a flashing problem versus a shingle problem?
How long does flashing last in Alberta’s climate?
Can flashing be repaired without replacing surrounding shingles?
We had a new roof installed two years ago and it’s leaking again. Could it be flashing?
Is chimney flashing different from regular roof flashing?
My roof has had multiple tar patches over the years. Is that a problem?
