Boston Accessory Dwelling Unit Guide
Data version: Q2 2026 · Last updated 2026-05-13
Buildability City Score™: C+ (Middle 55%) · Median permit time: 105 days
TL;DR. Find out if your Boston property qualifies for an accessory dwelling unit. Buildability™ checks the local ADU ordinance, Massachusetts state law, your zoning district, lot size, setbacks, parking requirements, and owner-occupancy rules in about 20 seconds. Free for your first check.
Boston ADU rules at a glance
Boston follows local ordinances layered on top of Massachusetts state ADU law. Typical restrictions cover maximum size (often 800–1,200 sqft), height (16–25 feet), side setbacks (4 feet minimum in most jurisdictions), parking (often waived near transit), and owner-occupancy. Buildability™ reads Boston's specific code against your exact lot.
Why this matters
Most Boston homeowners don't discover their ADU is infeasible until they've spent $3,000+ on preliminary design. Buildability™ catches the blockers first — easements, overlays, wetland proximity, utility extension costs — so you don't waste soft costs on a dead-end project.
How Buildability™ checks your Boston property
Enter any Boston address. Buildability™ pulls zoning, lot dimensions, easements, environmental overlays, utility access, and current Massachusetts state ADU law. Results include your Buildability Score™, setback envelope, maximum ADU size, parking waiver eligibility, and an estimated permit timeline — in about 20 seconds. Free for your first check.
Help us keep this accurate
Buildability™ translates Boston's ADU rules in plain language. Rules change and overlays are sometimes missed — if you spot an error on this page, email team@buildability.us with the URL and what's off. We verify with the Boston planning department and update within 48 hours of a confirmed correction. Boston planning staff: the same email works if you'd like to flag corrections or set up a direct verification channel.
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