ADU Craft Boston
ADU builder · Boston, MA

Add a second home to your Boston-area lot.

Backyard cottages, garage and carriage house conversions, additions, and basement or attic apartments for homeowners in Boston, Quincy, Newton, Somerville and Brookline. One contract covers design, permits and construction. Licensed and insured.

Check my lot See ADU costs
Small backyard home (ADU): A wood building with a glass roof
Licensed & insuredMassachusetts licenses this work through the Construction Supervisor License and Home Improvement Contractor registration. Our details come with every quote.
Permits handledPlans, energy paperwork and the building department review are on us.
Written, itemized quoteEvery line priced on paper before any work begins.

How much does an ADU cost in Boston?

As of October 2026, the Massachusetts Clean Energy Center's ADU guide puts a two-bedroom detached ADU at about $250,000 to $450,000 and an interior conversion at about $120,000 to $270,000, including site work. Design, surveys and permits often make up 10 to 20 percent of the budget. We price your lot in writing.

Read the Boston ADU cost guide

What kind of ADU can I build near Boston?

As of October 2026, state law lets owners in single-family zones of Quincy, Newton, Somerville and Brookline add an ADU of up to 900 sq ft, or half the main home's floor area if that is smaller, without a special permit. The City of Boston writes its own zoning and, outside Mattapan, allows ADUs only inside existing space for now.

Small backyard home (ADU): Green trees near white house Detached ADUA new cottage in the yard, separate from the house. Small backyard home (ADU) Garage or carriage house conversionReuse an outbuilding you already own. Small backyard home (ADU) Attached ADUAn addition with its own door, kitchen and bath. Finished attic room: A room with two beds and a rug on the floor Basement or attic ADUA unit carved from space inside the house. The main path in Boston today.

How ADU design and permits work · Compare every ADU type

How does an ADU project work?

  1. Lot checkYou send an address. We read the zoning, the transit distance and any historic or flood overlay.
  2. Visit and designWe measure the house and yard, then draw a plan sized to the rules and your budget.
  3. PermitsWe file with your building department and answer every comment.
  4. BuildConstruction, inspections and the certificate of occupancy.

See the full process

Where do we build ADUs?

Boston and four neighboring cities and towns. The state sets one floor for most of them, but each writes its own local details on top.

Boston

Its own zoning code. Interior ADUs citywide, detached units by right in Mattapan.

Boston ADU rules

Quincy

Four Red Line stations and a long shoreline both shape what a lot needs.

ADUs in Quincy

Newton

Local rules that go past the state floor, including ADUs in carriage houses by right.

ADUs in Newton

Somerville

Backyard cottages have been part of local zoning since 2019.

ADUs in Somerville

Brookline

A 2026 bylaw update with footprint caps and a short-term rental ban.

ADUs in Brookline

Check what your lot allows

Send your address and a line about your plans. We look up the zoning, the size cap and any overlay, then tell you which ADU types are realistic. Serving Boston, Quincy, Newton, Somerville and Brookline.

Boston-area ADU questions

How much does an ADU cost in Boston? Can I build an ADU in the City of Boston? What does the Massachusetts ADU law allow? Do I need to add parking for an ADU in Massachusetts? Can I rent my ADU short-term in Massachusetts? How much rent can an ADU make in Boston?