Boston & North Shore Roofing
Chimney Flashing Repair in Boston, MA
Shingles rarely fail first. The joints do, where the roof meets a brick chimney, a sidewall, a dormer or a parapet. We strip those joints back, rebuild them in proper metal, and test them with water before we call it done.
- Counter flashing cut into the mortar
- New metal, never reused flashing
- Crown and repointing above the roof line
- Water tested before we leave the job
Most Boston roof leaks are not shingle failures. They start where the roof meets something else: a brick chimney, a sidewall, a dormer, a parapet. Flashing is the metal that seals those joints, and it goes first.
It fails quietly. The roof looks fine from the street while water runs down the back of the chimney. By the time a ceiling stains, the sheathing around that stack has been wet for two winters.
We rebuild those joints across Boston and the surrounding towns, from porch-stack chimneys on three-deckers to clustered brick on the Hill.
- Counter flashing cut into the mortar
- New metal, never reused flashing
- Crown and repointing above the roof line
- Water tested before we leave the job
Free Flashing & Chimney Repair Estimate
Know The Signs
Signs the leak is your flashing, not your shingles
Flashing leaks have a signature. These are the ones we get called for most.
It only leaks in driving rain
Wind pushes water sideways into a joint that sheds a vertical downpour fine. If the ceiling only wets in a nor'easter, start at the flashing. Here is [why a roof leaks in heavy rain](/blog/why-does-my-roof-leak-only-in-heavy-rain/).
Black roof cement smeared at the chimney
Tar is not flashing. It is what somebody used instead. Roof cement goes brittle, cracks through one winter, and hides the failed joint.
A dark stripe running down the brick
Water is soaking into the masonry itself. That points at a cracked crown or open mortar joints above the roof line, not the metal.
Spalling brick and crumbling mortar
Faces popping off brick mean water froze inside it. Boston sits at or below freezing about 92 days a year, but only 23 stay frozen all day.
Rot low on a sidewall, no ceiling stain
Classic missing kick-out flashing. Where a slope dies into a wall that keeps going, water runs behind the siding instead of into the gutter.
Why parapets and chimneys leak first in Boston
The three-decker matured around 1890 in Dorchester and stopped going up by the 1930s. Survivors are sheathed in boards, with party walls running past the roof as brick parapets.
That parapet is the leakiest detail in the city. When the cap loosens, water runs inside a wall shared with the neighbors. On Dorchester three-deckers we rebuild the turn-up, termination bar and cap metal, tied into the EPDM center deck.
The details we rebuild most
Step flashing at sidewalls and dormers
Small L-shaped pieces, one per shingle course, each lapped over the one below. Done wrong it is a single aluminum strip bent into the corner and caulked.
Counter flashing at the chimney
Base flashing sits on the roof. Counter flashing covers it and tucks into a cut mortar joint. On older chimneys that reglet is packed with folded lead, worth saving.
The cricket behind the stack
A framed saddle that splits water and snow around the uphill side of a chimney. Plenty here never got one, and the shingles behind them show it.
Where the roofer stops and the mason starts
We flash chimneys, rebuild cracked crowns, repoint above the roof line and set caps. We do not reline flues or rebuild a stack from the firebox up.
Many Boston chimneys are dead anyway: capped flues left from coal or an old oil burner. If nothing vents, dropping the stack below the roof line beats reflashing it.
Historic districts, copper and matching metals
Copper is the traditional flashing metal here, and on Beacon Hill's clustered brick chimneys often the only one approved. That district dates to 1955, the first in Massachusetts, and Landmarks approval precedes the ISD permit.
Metals have to agree. Copper fastened with galvanized nails corrodes galvanically, so copper takes copper. Within 3,000 feet of saltwater in Marblehead and Swampscott, stainless is the spec.
Red flags on a flashing quote
- A price quoted by phone with nobody on the roof
- Roof cement or caulk written up as the repair
- Old flashing reused under brand-new shingles
- Nothing in the scope about the crown, cap or mortar
- Any offer to cover your deductible, illegal in Massachusetts
We are licensed and insured in Massachusetts, with HIC and CSL credentials on every estimate. A chimney on a pre-1940 slope usually means slate roof repair at the tie-in, and a leaking skylight needs proper curb flashing, not caulk.
Our Process
How we repair chimney and roof flashing
Flashing is detail work. We run it in the same order every time.
Find the real entry point
Water travels along rafters before it drops. We start inside at the stain and work uphill. A chimney leak often enters two feet above where it shows.
Inspect the masonry, not just the metal
We check the crown, the cap, the flue tile and the mortar above the roof line. If the brick is drinking water, new flashing will not stop the leak.
Strip the old joint out
Shingles come up around the stack, old flashing and cement come off, and we probe the deck for rot. Old flashing is never reused.
Cut a real reglet
Counter flashing gets set into a saw-cut mortar joint, wedged and sealed. Surface-caulked counter flashing is a two-year fix at best.
Weave step flashing course by course
One piece per shingle course, lapped up the wall, with a kick-out at the eave end. Never one long L-strip bent into the corner.
Water test, then hand over photos
We run a hose from the low side up, one zone at a time, with someone watching inside. You get photos of the open joint.
On The Roof
What flashing & chimney repair looks like in progress
What Drives The Price
What chimney and flashing repair costs in Greater Boston
This work prices by the joint, not by the square. Here is what moves it.
How much has to come apart
Reflashing a chimney means opening the shingles around it. On a brittle twenty-year-old roof, more of them break on removal and go back new.
Which metal you use
Aluminum is the common spec and it is fine. Copper costs several times more, lasts decades longer, and is what a historic district expects.
Condition of the masonry
New flashing on a chimney that needs a rebuilt crown or repointing is money spent twice. That work prices as its own line.
Cricket and geometry
A chimney more than 30 inches wide across the slope needs a cricket behind it. That is framing, sheathing, membrane and formed metal.
Coastal fastener spec
Within 3,000 feet of saltwater we use 300-series stainless. Copper nailed with galvanized fasteners corrodes galvanically, so the metals must match.
Cost drivers, not a quote. Paulo Silva looks at the chimney himself before a number goes on paper. If a contractor offers to cover your insurance deductible, walk away. That is illegal in Massachusetts.
FAQ
Flashing & Chimney Repair questions we get asked
Straight answers, including the ones that cost us work sometimes.
Staining on the outside of the brick points at the crown or mortar. Water at the joint where the stack meets the roof points at the flashing. Often it is both.
We can, and it may hold a season. Sealant is a stopgap at a metal lap, not a repair, and freeze-thaw pulls it loose.
A straightforward flashing repair usually does not. Structural masonry work can. In a Landmarks district, visible chimney work needs Boston Landmarks Commission approval before ISD issues anything.
It is common and it is wrong. That metal has run through twenty New England winters. Replacing it while the roof is open costs little.
Sudden storm damage often is. Slow deterioration from freeze-thaw and tired mortar reads as maintenance and generally is not. We photograph everything either way.
Related roofing services
Work that often comes up on the same roof.
- Roof RepairWe find the actual source of the leak, not just the stain below it, then repair valleys, flashing and rotted decking so it holds.Learn more
- Slate Roof Repair & RestorationSlate, copper and historic roof work. Matched stone, copper hooks and bibs, no tar patches, and historic review handled before the permit is pulled.Learn more
- Skylight Installation & RepairNew skylights, sun tunnels and skylight leak repair. Matched flashing kits, membrane-wrapped openings, and a water test before we leave.Learn more
Read more before you decide
Longer guides on the parts of this that homeowners ask about most.
- DiagnosisWhy Does My Roof Leak Only in Heavy Rain? The Flashing Failures Behind Boston LeaksIf your ceiling stains during a nor'easter but stays dry in a drizzle, the shingle field is probably fine. Six failure points that only leak under volume, wind, or both — and why the stain is never under the hole.5 min read
- Historic RoofingReplacing a Roof in Beacon Hill, Back Bay or the South End: Landmarks Commission Approval FirstDesign review is not a formality you handle later — Boston is explicit that Landmarks approval comes before the building permit. Here are the districts, what gets reviewed on a roof, and how to sequence the job.6 min read
Flashing & Chimney Repair across Greater Boston
We run this service in 34 communities. Here is where it comes up most often:
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