Rowley has no sewer, so every addition starts at the septic tank

Rowley's Board of Health adds its own requirements to Title 5: systems at least 30 feet from every lot line including the street, 100 feet from wetlands, none within 200 feet of the Mill River, and a design flow of at least 150 gallons per day per bedroom. Any repair or upgrade has to bring the whole system to new-construction standards. Every added bedroom or ADU has to pass that math first, so confirm the current regulations with the Board of Health. More in our guide to Title 5 and adding bedrooms.

Exterior work in the Central district around the Town Common and in the Glen Mills district needs Historic District Commission approval before the building permit. The guidelines are specific: wood clapboard at a 4-inch exposure, no vinyl or aluminum siding, rear shed dormers held 3 feet in from the gable ends, decks out of street view, chimneys kept. Paint color and roof color are not reviewed. Our historic renovation page covers how we prepare an application.

Outside the districts, the Historical Commission still reviews demolition. If it finds a structure significant after a public hearing, no demolition permit can issue for nine months. That can include an old barn or ell you planned to remove to make room for an addition, so ask before the schedule depends on it.

State law and the Inspections Department's April 2026 guidelines allow one ADU by right on a lot in a single-family district: attached, detached, or converted from a garage or barn, up to 900 sq ft or half the house, whichever is smaller. The guidelines bar rentals of 31 days or less, require one parking space unless the lot is within half a mile of the train station, and ask for proof of Title 5 compliance with the permit. Confirm the current bylaw with the Inspections Department. The state rules are in our Massachusetts ADU law guide.

Rowley's wetlands bylaw reaches past the state act: isolated wetlands, vernal pools plus 100 feet around them, a 100-foot buffer, the 200-foot riverfront area and the Parker River/Plum Island Sound ACEC. By vote, the Conservation Commission can set a no-cut, no-disturb zone, typically 25 to 50 feet from a resource area. On a marsh-edge or wooded lot, that line can decide where an addition or a new leach field goes.

Rowley adopted the Stretch Energy Code effective July 1, 2020, and has not moved to the Specialized code. New houses need a HERS rating, and so does an addition of more than 1,000 sq ft of conditioned space. Smaller additions follow prescriptive insulation and air-sealing rules. See the stretch code and additions.