Roofing Contractors in Dorchester, MA

What we find when we strip a Dorchester three-decker

Nearly every one of these buildings has been over-roofed at least once. Under the top layer we find board sheathing with quarter-inch gaps between planks, brittle felt from the 1970s, and a flat center deck that was never tied into the hip correctly. The rot is rarely everywhere. It sits in three predictable places.

• The rear porch stack, where decades of runoff have soaked the boards behind the gutter return.
• The chimney and any old skylight curb, where flashing was replaced with roof cement instead of metal.
• The low edge of the flat deck, where ponding water sat against a lap seam every spring.
• Occasionally the hip corners, where the two systems meet and nobody ever ran a proper transition.

Flat center decks: EPDM, TPO and modified bitumen

The flat middle is where Dorchester roofs leak. Water finds an old lap seam, travels along a joist, and shows up two rooms away on the third-floor ceiling. We take these decks down to clean sheathing, correct the pitch toward the drain where the framing allows, and install a single-ply membrane with fully adhered or heat-welded seams. EPDM is the workhorse on a residential three-decker. TPO makes more sense on the mixed-use blocks around Fields Corner and the newer multifamily at Columbia Point. Our page on flat roof replacement in Boston walks through how we pick.

Slate on Ashmont Hill, Jones Hill and Melville Park

Those streets are not three-deckers. They are large Queen Anne and Colonial Revival singles with turrets, dormers, complex valleys and original slate that is often still sound. Under 780 CMR, slate can never be roofed over. It has to come off. The good news is that most slate calls we take in Ashmont Hill are failed valley metal or a dozen slipped tiles, and slate roof repair costs a fraction of a tear-off.

Ashmont Hill is a National Register district. That listing is not the same as design review: none of Boston's local historic districts and architectural conservation districts sit in Dorchester, so your shingle color is not going in front of the Landmarks Commission the way it would on Beacon Hill. If your specific building carries an individual Boston Landmark designation, check with the commission at 617-635-1935 before we order material.

Ice dams on a finished third floor

The third floor of a three-decker was finished long after the roof went on. Insulation got stuffed against the rafters, the eave was blocked, and the ventilation path disappeared. Boston sees about 92 days a year at or below 32 degrees but only about 23 that stay below freezing all day. That 69-day gap is the melt-refreeze cycle that builds a dam at your cold eave. We treat the cause with attic ventilation and insulation work rather than selling you a heat cable, and every asphalt reroof we do carries an ice barrier from the roof edge to at least 24 inches inside the exterior wall line, as 780 CMR requires. Our guide to preventing ice dams on a Boston triple-decker covers the rest.

The saltwater edge: Neponset, Port Norfolk and Columbia Point

The east side of Dorchester sits on the water. Port Norfolk, Neponset, the Savin Hill shoreline and Columbia Point are all inside the roughly 3,000-foot band where FEMA coastal guidance calls for 300-series stainless fasteners. Hot-dipped galvanized is the practical minimum out there. And never let a crew nail copper flashing with galvanized nails. The two metals eat each other, and you will be back at that chimney inside five years.

Permits, snow load and cost

Dorchester is Boston, so a reroof with no structural work goes through the ISD Short-Form Permit: $20 to apply plus $10 per every $1,000 of the work estimate. We file it, along with the liability certificate, the workers' comp affidavit and the site safety paperwork. You should never be asked to pull a homeowner permit for a licensed crew. Design ground snow load in Boston is 40 psf, verified from the 780 CMR Eighth Edition table, and worth confirming with the building official on any structural change.

Full three-decker roofs here land in a wide range depending on square footage, how much sheathing is bad, and whether the flat deck is in scope. We put the number in writing after we walk it. Current market context is in our breakdown of roof replacement cost in Boston, and if you own on the border we also cover roofing in South Boston and Jamaica Plain roof repair.