Metal Roof Leaking Around Chimney: Flashing Restoration

Why Your Metal Roof Is Leaking at the Chimney (and Why It’s Almost Never What You Think)

Rainwater sneaking through your ceiling after a storm isn’t usually about a bad metal panel or crumbling mortar-it’s about the thin layers of flashing that nobody thinks about until they fail. I’ve spent nearly two decades on Brooklyn roofs, and I can tell you with confidence that nine times out of ten, when a metal roof leaks around a chimney, the culprit is flashing that was either installed wrong from the start, worn out from years of freeze-thaw cycles, or just can’t keep up with how metal and brick move against each other. The good news is that once you understand what’s actually happening up there, the fix is straightforward.

Before you climb a ladder or call anyone, you can do a quick sanity check from inside your house and maybe from the ground with binoculars. Look in your attic after a hard rain-if you can trace the water stain or active drip back toward the chimney area rather than toward a skylight or ridge vent, you’re probably on the right track. Check the ceiling below the chimney on every floor; sometimes water travels along a rafter or down inside the chimney chase before it shows up two rooms away. If those clues point back to the chimney, and especially if the stains show up during wind-driven rain or after freeze-thaw days, it’s time to call a pro like Metal Roof Masters to get eyes on the flashing itself.

Here’s the blunt truth about metal roofs and chimneys: they’re made of materials that expand, contract, and age at completely different rates, and the only thing holding back thousands of gallons of water every year is a system of bent metal pieces and sealants that have to stay flexible while being baked by summer sun and frozen by January nor’easters. When I’m standing on a roof in Park Slope looking at a 100-year-old brick chimney poking through standing-seam panels, I’m basically looking at a slow-motion wrestling match where one side is rigid and crumbly and the other side is slick and wants to slide around. The flashing is the referee, and when it gives up, water wins.

What Flashing Actually Does (and Why It Fails)

Think of chimney flashing like the weather stripping around your front door-it’s supposed to create a flexible seal between two surfaces that move independently. On a metal roof, you’ve got step flashing running up the sides of the chimney, base flashing at the bottom, back flashing (often with a cricket or saddle) at the uphill side, and counter-flashing that tucks into the mortar joints and laps over everything else. When any one of those pieces gets a gap, lifted edge, or cracked sealant bead, water finds it. I’ve pulled off counter-flashing in Bay Ridge that looked fine from ten feet away but had a pencil-thin gap where wind-driven rain was shooting uphill under the metal panels every time a storm blew in from the harbor.

Metal roofs expand and contract more than almost any other roofing material. On a sunny July afternoon, those panels can be 30 or 40 degrees hotter than the brick chimney sitting in the shade of a taller building. Come January, the metal shrinks fast while the brick barely moves. Every cycle opens and closes tiny gaps at the flashing line. Sealants get hard and crack. Fasteners back out. Counter-flashing that was embedded in old lime mortar starts to wiggle loose because that mortar is basically sand at this point.

How to Confirm the Chimney Is Really Your Leak Source

On a cold Brooklyn morning, I’ll get a call from someone absolutely convinced their skylight is leaking, and after I trace the water back through the attic, we find out it’s been traveling six feet along a rafter from the chimney flashing the whole time. Water doesn’t fall straight down inside your house-it follows wood grain, drips onto insulation, and sneaks along the underside of sheathing until it finds a nail hole or seam to come through. So before you spend money on a repair, you need to play detective.

Start in the attic on a rainy day if you can do it safely. Bring a flashlight and look for wet insulation, dark streaks on rafters, or active drips. Trace any wetness back toward its highest point-that’s usually close to where it’s coming in. If that high point is near the chimney framing, you’ve got your answer. From the outside, use binoculars to check the counter-flashing around the chimney: look for gaps where it meets the brick, lifted edges, or places where the metal panels seem to be pulling away. You’re not trying to diagnose the exact failure mode-you’re just confirming that the chimney area is the problem zone so you’re not wasting time and money chasing ghosts.

If you notice water stains after a nor’easter, especially if they only show up when the wind is howling out of the east or southeast, that’s a huge clue that wind-driven rain is getting behind your flashing. Normal straight-down rain might not trigger the leak because gravity and good laps keep it out, but when rain is moving sideways at 40 miles an hour, it finds every weak spot. I’ve seen this a dozen times in Williamsburg and Greenpoint where buildings face the water and catch the brunt of coastal storms.

Why Metal and Brick Are a Tough Pairing (Especially in Brooklyn)

From a roofer’s point of view, that chimney is the enemy of a simple roofline. It interrupts the flow of water, creates uphill and downhill zones where everything wants to pool or shoot past, and introduces a second material that behaves completely differently from your roof panels. Metal roofs are designed to shed water fast with clean lines and overlapping seams. Chimneys are bulky, porous, and don’t care about your drainage plan. Flashing is the compromise, and it only works if it’s installed right and maintained over time.

One January in Bay Ridge, I got called to a three-story row house where the homeowner swore the roof was fine but water kept showing up inside the chimney chase every time the wind hit from the harbor. Turned out the original metal roof installer had just gooped sealant where the metal met the brick-no proper step flashing at all-so the freeze-thaw cycles had opened a tiny gap you could only see when the metal was cold and shrunk. I rebuilt the chimney flashing in 25-degree weather, metal snips in hand, heating the sealant with a small torch so it would set right, and that leak never came back. That job taught me that you can’t see a shrinkage gap in August when you’re up there for an inspection; you have to know it’s coming and build the flashing to handle it.

A summer job in Williamsburg sticks with me: a converted warehouse with a long, low-slope metal roof and a big square chimney serving half the building. The owner complained of mystery leaks that only happened during sideways rain. By climbing inside the attic bays and then back out on the roof, I tracked it to uplifted counter-flashing where wind-driven rain was being pushed uphill under the metal panels, sneaking in behind a poorly bent saddle flashing. I redesigned the whole flashing system around that chimney, adding a wider cricket and properly hemmed counter-flashing into the mortar joints, and we stopped what three other contractors had misdiagnosed as condensation. That warehouse sits low and catches wind off the East River, so the flashing had to be built like it was expecting a sideways car wash every few months.

The Three Usual Failure Points

Most leaks happen at the same three spots. The uphill side of the chimney-what we call the back-is where water hits hardest and pools if there’s no cricket to divert it around. If the back flashing is too shallow, flat, or missing a diverter, water just sits there until it finds a seam or nail hole. The sides are where step flashing has to climb the brick in a stair-step pattern, lapping with each metal panel as it goes up. If those steps are too far apart, nailed through instead of clipped, or just missing because someone thought sealant would do the job, water runs down the brick, hits the roof, and keeps going under the panel. The counter-flashing that covers all the base and step flashing is supposed to be tucked into mortar joints and sealed, but in old Brooklyn buildings, that mortar is often so degraded that the counter-flashing just hangs there like a curtain with a gap behind it.

Think of it like the expansion joints on the subway tracks. When it’s hot, metal grows, and when it’s cold, it shrinks. If you bolt everything down tight, something’s going to buckle or tear. Good flashing has to let the metal move a little while still keeping the seal-that’s why we use clips instead of nails where we can, and why sealants have to stay flexible for years. I always tell people to picture a winter pothole forming: water gets in a crack, freezes, expands, and makes the crack bigger. Same thing happens where your metal roof meets your brick chimney every single winter.

When Buildings Settle (Because They All Do)

In Clinton Hill, I restored flashing around a decorative brick chimney on a standing-seam metal roof where the building had settled on one side over the years. That small tilt meant the panels and the chimney were moving differently every season, popping nails and opening micro-gaps at the uphill side. I added a clever slip-flashing detail to let the metal float slightly while still staying watertight against the stationary brick, and I only know to look for that kind of structural shift because I’ve spent nearly two decades fixing “we already tried everything” leaks. Settlement is real in Brooklyn-these buildings are a century old, they sit on everything from bedrock to fill dirt, and they shift a quarter inch here, an eighth inch there. Your roof has to be able to handle that, or the flashing will tear itself apart over five or ten years.

Brooklyn Roof Reality Check:

• Harbor winds in neighborhoods like Bay Ridge and Red Hook push rain uphill under metal panels, so standard flashing laps aren’t always enough.
• Buildings in Brooklyn settle unevenly because of mixed soil conditions and age, which means your chimney and roof might be moving in different directions every winter.
• Old lime mortar in brownstone and row-house chimneys crumbles when you try to re-set counter-flashing, so repairs often require careful repointing before the flashing even goes in.

What a Proper Chimney Flashing Restoration Looks Like

Let’s talk about what should actually happen when a roofer like me shows up to fix your chimney flashing on a metal roof, because knowing the steps helps you tell the difference between a real repair and a guy with a caulk gun. First, we pull off the old counter-flashing carefully-sometimes we can reuse it if it’s still in good shape, but usually it’s bent, cracked, or was never the right profile to begin with. Then we inspect the step flashing and base flashing underneath; if those pieces are compromised, they come off too, which might mean lifting a few metal panels to access the fasteners. The brick gets cleaned and checked-any loose or missing mortar has to be repointed before new flashing goes in, or we’re just going to be back in two years doing it again.

Next, we fabricate and install new base flashing at the bottom of the chimney, making sure it laps over the metal panels correctly and has a good kick-out to keep water moving downhill. Step flashing goes in next, one piece tucked behind each panel as we work up the sides-each piece should overlap the one below it by at least three inches, and the top edge needs to turn up against the brick. If the chimney is big or the roof slope is shallow, we add a cricket at the back, which is basically a little metal tent that splits water around the chimney instead of letting it pool. Counter-flashing caps everything, gets hemmed into the mortar joints, and laps down over the base and step flashing by a few inches. We bed it in polyurethane or a high-grade elastomeric sealant that’ll stay flexible through a hundred freeze-thaw cycles, and then we make sure every seam and edge is sealed but not gooped so thick that it traps water.

Nine times out of ten, the leak isn’t where you think it is. That’s why a real restoration means checking the whole system, not just slapping sealant on the obvious crack. I’ve pulled off counter-flashing that looked perfect from the ground, only to find that the step flashing underneath was completely missing on one side because the original installer ran out of material and figured sealant would cover it. It did, for about three years, and then the homeowner called me.

Cost, Timing, and When to Call Metal Roof Masters

Let’s talk about money for a second. A proper chimney flashing restoration on a metal roof in Brooklyn typically runs between $1,200 and $3,500, depending on chimney size, how much of the flashing system needs replacement, whether we’re repointing brick, and how hard the roof is to access. If we’re just replacing counter-flashing and adding sealant because everything underneath is still solid, you’re on the lower end. If we’re tearing off panels, fabricating a new cricket, repointing mortar joints, and rebuilding step flashing on all four sides, you’re looking at the higher end or beyond. That might sound like a lot, but compare it to the cost of rotted roof sheathing, ruined insulation, mold remediation, and ceiling repairs after a year of uncontrolled leaks, and it’s a bargain.

Timing matters in Brooklyn because our weather swings hard. I don’t love doing flashing work in January unless it’s an emergency, because sealants don’t cure right below about 40 degrees, metal is brittle and hard to bend, and your fingers go numb in about eight minutes. Spring and fall are ideal-the metal panels are close to their mid-range size, the weather cooperates, and we can take the time to do detail work without racing a thunderstorm. If you’re seeing leaks right now, call Metal Roof Masters and get on the schedule; we can often do temporary sealing to get you through a rough season and then come back for the full restoration when conditions are better. If you’re just noticing stains from last winter and it’s dry now, don’t wait-book the work for late spring or early September so you’re buttoned up before the next round of nor’easters hits. I’ve seen too many people wait, thinking a small leak isn’t urgent, and then call me in a panic after three months of rain have turned their attic into a science experiment.

If you’re reading this because you’ve got a wet ceiling or you’re tired of putting buckets in the attic, reach out to Metal Roof Masters. We’ve been solving these exact problems all over Brooklyn for years. I’ll come take a look, show you exactly what’s going on in plain English, and give you a fair price to make it right. Most of the time, it’s not scary or complicated once you understand it-it’s just metal, brick, and a little bit of craftsmanship holding back the weather.