ADU CONSTRUCTION IN MASSACHUSETTS
Massachusetts changed the rules — you can now build an accessory dwelling unit on your property by right, no special permit needed. From backyard cottages to garage conversions and in-law suites, we design, permit, and build rental-ready ADUs.
GET FREE ESTIMATE
Free and no obligation. Tell us about your project.
WHAT'S INCLUDED
WHY CHOOSE INNOVATE BUILDING FOR ADU BUILDS
OUR PROCESS
Feasibility Review
We check your lot, zoning dimensional rules, utilities, and septic capacity — and tell you exactly what you can build.
Design & Permits
Architectural plans sized to the 900 sq ft / 50% rule, submitted for a standard building permit. No special permit required.
Construction
Foundation to finishes with our own crews — site work, utilities, framing, and interior build-out.
Rental-Ready Handoff
Final inspections, certificate of occupancy, and a unit ready for family or tenants.
FREQUENTLY ASKED QUESTIONS
Can I really build an ADU without a special permit in Massachusetts?
Yes. Since February 2025, state law allows one ADU up to 900 sq ft (or 50% of your home's floor area, whichever is smaller) by right on any single-family lot. You still need a standard building permit, but towns can no longer require a variance or special permit for a conforming ADU.
How much does an ADU cost to build?
In Greater Boston: basement conversions typically run $80K–$150K, garage conversions $120K–$220K, and detached new-construction ADUs $250K–$500K+ depending on size, site conditions, and finishes. We provide a fixed-price proposal after a feasibility visit.
Can I rent out my ADU?
Yes — long-term rentals are allowed, and towns cannot require you to live on the property. Short-term rentals under 31 days are not permitted under the state ADU law.
Do I need extra parking for an ADU?
Towns may require at most one additional space — and none at all if your property is within a half mile of public transit.
What if my home is on a septic system?
Title 5 capacity is based on bedroom count. We evaluate your system during feasibility; some projects need a septic upgrade, which we price up front — no surprises mid-project.
How long does an ADU project take?
Design and permitting typically take 6–10 weeks, and construction 3–6 months depending on the type — garage and basement conversions are fastest, detached cottages take longest.