ADU Builders in Massachusetts and Greater Boston
Massachusetts legalized accessory dwellings statewide in February 2025, and the builder market caught up faster than anyone expected. Most single-family lots can now add a unit of up to 900 square feet by right, with no special permit, and MassHousing followed with a loan program. The result is a young market with unusually clear rules and a real crop of ADU-first firms rather than remodelers who added a service page. The local problems are frost-depth foundations, wiring in houses built long before anyone imagined a second kitchen, and a season that closes. This page covers Greater Boston, the North and South Shores, Worcester and the Cape.
- 1
Massachusetts-based custom stick-built ADU builder with over 40 years of residential construction experience, specializing in fully finished units delivered in 100 days or less.
- 2
Worcester-based design-build firm specializing in ADU and in-law apartment construction, handling the full process from design through permitted installation on your property.
- 3
Award-winning design-build firm on the South Shore specializing in custom ADUs and whole-home remodeling, with over 20 years of comprehensive site-built construction experience.
- 4
Design-build firm based in Easthampton, MA that specializes in constructing affordable, net-zero-ready accessory dwelling units on existing properties across western Massachusetts and New England.
- 5
Boston-area custom ADU builder focused on stick-built construction for Boston's tight urban and suburban lots, with personalized design services and ADU-specific financing guidance.
- 6
Stick-built ADU constructor serving Massachusetts, Connecticut, and Rhode Island, building permanent site-constructed accessory dwelling units directly on customer property.
- 7
Design-build firm specializing in ADU construction across Boston's western suburbs, with expertise in conversions, detached units, and attached additions for multigenerational living and rental income.
- 8
Licensed design-build firm on the South Shore with 30+ years of construction supervision, offering integrated design, permitting, and ADU construction for homeowners seeking a single, experienced point of contact.
- 9
Design-build firm on Cape Cod that adds accessory units to single-family properties, with licensed construction expertise and a focus on aging-in-place accessibility for Massachusetts homeowners.
- 10
Framingham-based design-build firm where in-house architects collaborate directly with contractors to design and construct custom ADUs across MetroWest, serving towns from Boston to Hopkinton.
- 11
Licensed CSL/HIC general contractor with 25 years in greater Boston, offering detached, attached, garage conversion, and basement ADUs alongside remodeling and custom home work.
- 12
Millis-based ADU construction specialist focused exclusively on accessory dwelling units throughout Massachusetts, offering consultation, permitting, and full construction services.
- 13
Custom home builder founded by Allen Carpenella, serving greater Boston with ADU construction alongside renovation and new-build work, emphasizing transparency and long-term client relationships.
- 14
Milford-based general contractor owned and operated by Marcos Damasceno, serving MetroWest with design-led construction of residential renovations and ADUs across 40+ towns.
- 15
Wellesley Hills-based luxury custom builder and renovator with 17+ years of experience designing and building energy-efficient high-performance homes and ADUs across MetroWest and inner Boston suburbs.
- 16
Full-service design-build firm in Southeastern Massachusetts that constructs ADUs alongside kitchen and bathroom remodels, serving Plymouth and Cape Cod with a reputation for reliable execution and attention to detail.
- 17
Southern Berkshires design-build firm specializing in custom homes and ADUs using healthy building principles, superior materials, and thoughtful craftsmanship.
Frequently asked questions
What are my options if I want to convert an existing space rather than building something new?
Several firms specialize in conversions, including those focused on garage conversions, basement ADUs, or transforming existing structures into in-law apartments. You can also find builders who specialize in attached additions designed for multigenerational living.
I have a very small lot in an urban area. Can I still build an ADU?
Yes. Certain builders focus specifically on stick-built construction tailored for tight urban and suburban lots found around the Boston area. These specialists work with personalized designs to maximize utility in limited spaces.
Do the builders listed handle the complicated permitting process in Massachusetts?
Most of the design-build firms on this list provide integrated services that include permitting and consultation. They handle the process from the initial design through the permitted installation on your property.
Can I find a builder that focuses on eco-friendly or sustainable construction?
You can find specialists that focus on constructing affordable, net-zero-ready units. These builders are equipped to handle sustainable accessory dwelling units on existing properties throughout New England.
Are there builders who specialize in making homes more accessible for elderly family members?
Yes. Some firms focus specifically on aging-in-place accessibility to help Massachusetts homeowners accommodate senior living. These builders specialize in adding units that prioritize ease of movement and long-term usability.