Garage conversion rules in Boston, MA — sometimes called garage-to-ADU or accessory living unit conversions — govern permits, ceiling height, egress, and parking replacement.
Garage conversions to ADUs are explicitly allowed under the 2024 MA Affordable Homes Act by right on single-family zoned lots, subject to building code compliance and permit requirements.
The 2024 Affordable Homes Act specifically includes garage conversions as a permitted ADU type. Converting a garage to living space requires a building permit and compliance with 780 CMR including egress windows, insulation, electrical, plumbing, and fire safety requirements. The conversion cannot exceed 900 square feet or 50% of the principal dwelling. Boston's zoning may require site plan review but cannot require a special permit for the ADU use itself. Parking displacement from garage conversion cannot trigger denial if the lot is within half a mile of MBTA transit. The unit must meet all state sanitary code standards for habitation.
Unpermitted conversions subject to ISD enforcement including fines and required remediation. Uninspected conversions may not receive certificate of occupancy. Insurance and sale complications.
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Side-by-side rule comparisons with other cities in Suffolk County.
See how other cities in Suffolk County handle garage conversions.
See how Boston's garage conversions rules stack up against other locations.
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