Brookline ADU feasibility
Brookline follows the statewide by-right ADU rules.
Rules cited for Brookline
- One protected ADU is allowed by right on a lot in a district that allows a single-family house by right or by special permit. A second unit needs a special permit.
- The by-right gross floor area is the smaller of 900 square feet and half the principal dwelling. A town cannot set a lower cap, and it may allow a larger unit.
- The town cannot require the owner to live in either unit, and it cannot require a family relationship.
- Parking is at most one extra space. If any part of the lot is within 0.5 miles of a commuter rail station, subway station, ferry terminal, or bus station, no extra space may be required.
- Setbacks, coverage, open space, bulk, height, and stories cannot be stricter than the most permissive standard for the principal dwelling, a single-family dwelling, or an accessory structure. A minimum lot size and a floor-area ratio for the protected unit are not allowed.
- Brookline is covered by the state rule. In a June 18, 2025 decision, the Attorney General disapproved bylaw text that made ADU dimensions follow the principal dwelling when the accessory-structure standard was more permissive. Brookline has to use the more permissive of the principal dwelling, a single-family dwelling, or an accessory structure.