Tiny Homes in Boston, Massachusetts

Boston is its own zoning jurisdiction and the statewide Affordable Homes Act ADU provisions do not apply automatically — the city administers its own ADU rules through the Boston Zoning Code. As of April 2026, Boston allows ADUs citywide with detached, attached, and internal configurations permitted on most single- and two-family lots; ADUs must generally be at least 350 sq ft and no more than 900 sq ft or 50% of the primary dwelling, whichever is less. A building permit, plumbing permit, electrical permit, and Certificate of Occupancy are required from the Inspectional Services Department (ISD). One off-street parking space is required for each ADU, waived if the property is within a half-mile of an MBTA rapid-transit or commuter rail station. THOWs are regulated as recreational vehicles and cannot serve as a primary residence on standard Boston residential lots. Tiny homes of 400 sq ft or less built on permanent foundations may use the Appendix AQ code pathway from the 10th Edition of 780 CMR. Verify current requirements with your local planning department before purchasing land or beginning construction.