Boston & North Shore Roofing
Flat Roof Replacement in Boston, MA
Boston's flat roofs do not shed water or snow. They hold it. When an old rubber or tar roof finally gives up, the leak lands in a top-floor ceiling and the patching stops working.
- 60-mil EPDM, fully adhered and taped
- Tapered insulation kills ponding water
- Board-sheathing repair on century-old decks
- Boston ISD short-form permit filed for you
Most Boston roofs that leak are not the steep ones. They are flat. The three-decker deck, the rear ell, the mansard top behind a cornice, the row-house roof behind a parapet.
No flat roof is truly flat. It is built to drain at about a quarter inch per foot. Twenty winters of settling framing and compressed insulation flatten that out. Then water stands and seams soak.
We tear off and replace low-slope roofs in 60-mil EPDM rubber. Paulo Silva walks the roof and writes the estimate himself.
- 60-mil EPDM, fully adhered and taped
- Tapered insulation kills ponding water
- Board-sheathing repair on century-old decks
- Boston ISD short-form permit filed for you
Free Flat & Low-Slope Roofing Estimate
Know The Signs
Signs your Boston flat roof is past patching
A flat roof warns you before it fails. Every warning sits up on the roof, where nobody looks.
Water still standing two days later
EPDM tolerates a damp low spot. It does not tolerate a puddle that never leaves. Standing water 48 hours after rain means the slope or the drains are gone.
Seams you can lift with a finger
Lap seams fail first on an old rubber roof. Freeze-thaw pries them open a fraction at a time, then wind gets under the edge.
Membrane shrunk back from the walls
Old EPDM pulls inward as it ages. Rubber stretches tight over the corners and flashing drags off the parapet. Once the perimeter is under tension, every detail is failing.
Soft, spongy spots underfoot
Give underfoot means saturated insulation and board sheathing rotting beneath it. Wet insulation does not dry out under a rubber roof. It spreads.
Ice sitting on the deck into March
A flat roof stores the whole snowfall instead of shedding it. Meltwater refreezing at a cold parapet is a load problem and a leak problem at once. Start with [ice dam removal and prevention in Boston](/services/ice-dam-removal-boston/).
Why EPDM rubber on a Boston three-decker
EPDM is a rubber sheet. Rolled out in big pieces, bonded to the insulation, laps joined with seam tape. No torch and no hot kettle over an occupied three-family. We install 60-mil, not 45-mil, because people walk these roofs.
TPO and PVC are heat-welded rather than taped, and both work well on bigger buildings. Compare them in our EPDM vs TPO vs PVC guide for Boston flat roofs. For a condo association or an old mill, start with commercial and multi-family roofing.
The Boston flat roof, building by building
Triple-deckers and three-families
The three-decker matured around 1890 in Dorchester, and construction stopped region-wide by the 1930s. Every one still standing is 100 to 140 years old, with board sheathing that has gaps between the boards and will not hold a fastener like plywood. We work on flat roofs in Dorchester and triple-deckers in South Boston year round.
Mansards in the South End and Back Bay
A mansard is two roofs pretending to be one: slate or metal on the near-vertical face, low-slope membrane on the flat top behind it. These blocks have continuous rooflines, so your flat top ties into the neighbors' on both sides. The face is slate and historic roof restoration work, and Landmarks Commission approval comes before the ISD permit.
Snow load, freeze-thaw and the code that applies
A pitched roof sheds snow. A flat roof stores it. The 780 CMR Eighth Edition table sets design ground snow load by town: 40 psf for Boston, Cambridge, Somerville, Brookline, Quincy and Revere, 50 psf for Danvers, Ipswich and Gloucester. Confirm your town's number with the building official.
Freeze-thaw does the slower damage. Boston sits at or below freezing about 92 days a year, but only about 23 stay frozen all day. That 69-day gap melts water into a lap seam and refreezes it the same night. It is the mechanism that opens parapet and chimney flashing.
One code point worth knowing. The ice barrier rule at 780 CMR R905.1.2, underlayment from the lowest edge to at least 24 inches inside the exterior wall line, is written for shingles, slate and wood shakes, not for a fully adhered rubber field. It does govern the pitched section your flat roof ties into. That tie-in is what leaks in February.
Red flags on a flat roof bid
- A coating quote with no moisture scan. Silicone over wet insulation seals the water in.
- No mil thickness or attachment method on the estimate.
- No permit. In Boston the contractor files the short form.
- Any offer to cover your insurance deductible. That is illegal in Massachusetts.
- No HIC or CSL shown. Both are free to verify with the state.
Call (209) 758-8550 and Paulo will come look at the roof. The estimate names the membrane, the thickness, the insulation and every flashing detail, in writing.
Our Process
How we replace a low-slope roof in Boston
Same sequence every time, on a Dorchester three-decker or a South End rear roof.
Core sample and moisture check
Paulo walks the roof, checks the drains and probes for soft insulation. On a multi-layer roof we cut a small core so we know what is actually under there.
Permit and paperwork
Boston ISD issues a short-form permit for a reroof with no structural work: $20 to apply plus $10 per $1,000 of the estimate. We file it, with our trade license and insurance certificate.
Staging and protection
This is what gets underpriced on a three-decker. Four stories of staging, a rear porch stack in the ladder line, party walls on both sides, nowhere legal for a dumpster.
Tear-off and deck repair
Membrane, felts and gravel come off so we can see the sheathing. Century-old decks are boards, not plywood, and usually need some replaced. A Specialty CSL for roof covering allows up to 25 percent.
Insulation and slope correction
New polyiso goes down, with tapered sections and crickets behind chimneys where the deck has gone flat. This is the step that ends ponding water. Skipping it is why the last roof failed.
Membrane, flashing and a water test
60-mil EPDM, fully adhered, seams taped and rolled. Then termination bar at the parapets, new edge metal, pipe boots, curb flashing at skylights. We run water on it before we call it done.
On The Roof
What flat & low-slope roofing looks like in progress
What Drives The Price
What drives flat roof replacement cost in Boston
Flat roof replacement in Greater Boston generally lands between roughly $7,000 and $17,000 per 1,000 square feet installed. The membrane is the cheap part. Here is what moves the number.
How many layers come off
One old rubber membrane is a clean tear-off. Three layers of built-up felt and gravel is a different job, with far more weight in the dumpster and far more disposal cost.
Deck condition
Board sheathing on a 1905 three-decker usually has rot at the perimeter and around old drains. We price an allowance and show you every board we replace.
Insulation and tapered slope
New polyiso, tapered sections and crickets are a real line item, and the one owners are tempted to cut. It is also the difference between a roof that drains and one that ponds.
Access and staging
A South End roof with no dumpster space and four stories of staging costs more to reach than a Saugus ranch with a driveway. Tight alleys and party walls add labor hours.
Metal, drains and penetrations
Edge metal, coping caps, scuppers, pipe boots and skylight curbs are where the craft lives. Coastal buildings need stainless fasteners, a small cost with a large payoff.
These are Greater Boston ranges from the roofs we actually work on, not a quote. Every flat roof prices differently once we see the deck and the access.
FAQ
Flat & Low-Slope Roofing questions we get asked
Straight answers, including the ones that cost us work sometimes.
A properly installed 60-mil EPDM roof with real slope gives 20 to 30 years here. The membrane rarely fails first. Flashing, drains and parapet details decide whether you get 12 years or 28.
Sometimes, but rarely on residential low-slope. If the insulation underneath is wet, covering it seals the water in and rots the board deck. We cut a core sample first and show you what comes back.
A damp low spot after a downpour is normal. Water still sitting there two days later is not. Most manufacturers exclude long-term ponding from warranty coverage, so a bid that never mentions slope is selling you the same roof again.
Yes, and we file it. A residential reroof with no structural work runs on a Boston ISD short-form permit. In a landmark district, Landmarks Commission approval has to come first.
Related roofing services
Work that often comes up on the same roof.
- Commercial RoofingTPO, PVC, modified bitumen and silicone restoration for condo associations, mill buildings, churches and retail plazas. Board-ready scopes and phased work that keeps tenants operating.Learn more
- Flashing & Chimney RepairStep, counter and cricket flashing rebuilt at chimneys, sidewalls and parapets. Crown and mortar repair above the roof line, water tested before we leave.Learn more
- Ice Dam Removal & PreventionSteam ice dam removal, roof snow raking and the attic work that stops the dam from coming back. Photos and dates for your insurance file.Learn more
Read more before you decide
Longer guides on the parts of this that homeowners ask about most.
- MaterialsEPDM vs. TPO vs. PVC: Choosing the Right Flat Roof for a Boston Triple-DeckerMost of Boston's housing has a flat or near-flat deck, which makes membrane choice a real decision. Here is how EPDM, TPO and PVC actually differ — and why the tapered insulation under them matters more than the sheet itself.6 min read
- WinterHow Much Snow Can a Massachusetts Roof Hold? Boston's 40 PSF vs. the North Shore's 50 PSFMassachusetts rates roofs in pounds per square foot, not inches. Boston sits at 40 psf and the northern North Shore at 50. Here is what those numbers mean for your roof this winter, and the warning signs that matter.5 min read
Flat & Low-Slope Roofing across Greater Boston
We run this service in 34 communities. Here is where it comes up most often:
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