Massachusetts ADU feasibility checker

Enter a Massachusetts address or a town, plus the lot size, the existing house size, and the lot type. The screen applies the 2024 by-right accessory dwelling unit rules and any town limit cited from an official page.

Not legal advice. This is not legal advice. It is a screening summary of the Affordable Homes Act (Chapter 150 of the Acts of 2024), the EOHLC regulations at 760 CMR 71.00, and the local pages cited here. It is not a permit or a zoning opinion. EOHLC does not answer questions about a specific property. Setbacks, lot coverage, the building code, the fire code, Title 5 septic rules (310 CMR 15.000), wetlands, flood zones, and historic review can change the outcome. Confirm the parcel with the city or town and a licensed professional before you spend money on plans. HLC has proposed revisions to 760 CMR 71.00; public comment closed on October 9, 2026. This screen uses the regulations published in the Massachusetts Register on January 31, 2025, which took effect February 2, 2025, not that draft.

Massachusetts address

Or leave this blank and choose a town below.

Town

Lot size (sq ft)

Existing house gross floor area (sq ft)

Include basements with legal ceiling height. Exclude crawl spaces, garages, attics, and enclosed porches.

Lot type

Single-family zoningThe district allows a single-family house by right.Single-family zoning, within 0.5 miles of a transit stationAny part of the lot is within 0.5 miles of a commuter rail station, subway station, ferry terminal, or a regular bus station. A flag stop does not count.Single-family zoning in a local historic districtZoning may still allow the unit. A historic district can require a separate design review.District allows single-family homes, and the house is a 2- or 3-familyThe by-right unit is not limited to lots that contain only a single-family house.Zoning does not allow single-family homesBusiness or industrial districts that do not allow a single-family house are outside the state by-right rule.

Massachusetts ADU feasibility checker

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