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Boston-area ADU questions, answered
Each guide gives the short answer first, then the detail and the cases where it depends. Rules and numbers carry a date and a source.
Updated October 2026
How much does an ADU cost in Boston?
Published 2026 ranges by ADU type, the soft costs on top, and incentives that can help.
Read the guideCan I build an ADU in the City of Boston?
Boston's own rules: interior units citywide, Mattapan, and the 2026 draft for three neighborhoods.
Read the guideWhat does the Massachusetts ADU law allow?
Size, by-right status, owner occupancy, entrances and what towns can still regulate.
Read the guideDo I need to add parking for an ADU in Massachusetts?
One space at most, none near transit, and what counts as a station.
Read the guideCan I rent my ADU short-term in Massachusetts?
What the state lets towns restrict, and how Brookline, Newton and Boston handle it.
Read the guideHow much rent can an ADU make in Boston?
Current Boston rents, and what decides what an ADU can earn.
Read the guideWant the answer for your own lot?
The guides cover general rules. Send your address and we apply them to your property.