Abacus

Abacus is a South Boston general contractor whose name comes up again and again for one particular kind of job: the roof deck. Dozens of reviews — spanning additions, gut renovations, porch rebuilds, and roofing work — repeatedly name the same crew: Mark Little, Gerald, Lua, and Ger. Its Massachusetts home improvement contractor registration is active, and the Better Business Bureau gives it an A+ grade. On Google, its 87 ratings average 4.9★, and Houzz shows a 5.0★ average from 5 ratings. The specifics run deep: in a November 2025 review, neighbors had been quoted $50,000–$100,000 to fix a roof leak, until Mark found and patched an opening in the rubber roof membrane for a few hundred dollars. Reviewers describe Abacus taking over work other contractors left unfinished — in a 2024 review, new owners of a Beacon Hill condo hired the company to fix a prior contractor's unpermitted, defective porch rebuild; in a 2025 review, a real-estate development company brought Abacus in after a previous general contractor abandoned a five-unit condo conversion mid-demolition. Multi-month, multi-trade projects come up often too — a nine-month full renovation of a South End row house, a large condo project that required tracing a water-vapor-barrier defect back to the original builder — and one reviewer says a property management company has hired the firm for close to two decades. There is one clear miss on record: in a February 2024 review, a homeowner said Abacus gave its ironworking subcontractor the wrong plans, resulting in a roof-deck staircase installed on the wrong side of the house, and that the company refused to fix it or take responsibility. It stands out because it's the lone complaint against dozens of detailed, positive accounts, not a pattern — still worth asking about directly. For a roof deck, a porch, or a larger gut renovation in the South Boston area, the volume and specificity of the reviews point to a crew that takes on complicated, multi-trade jobs and finishes what other contractors couldn't.