Best ADU Builders in Massachusetts

BuildX is the cleanest verification in this state, and in Massachusetts that sentence means more than it does anywhere else, because there are two credentials to get right and most companies only make one of them easy to find.

Here is the pair. The business holds HIC registration 208169, active, effective March 2025 and running to March 2027, registered in Carver. The responsible person named on that registration is Vittorio M Artiano, and he holds Construction Supervisor Licence CS-042906, active, and it is the unrestricted type rather than the 1 and 2 Family or Specialty variants. That last detail matters: a Specialty licence is a restricted trades credential and would not cover general building supervision on your ADU.

The review record backs it up. 5.0 across 41 Google reviews is the deepest base I could verify in Massachusetts, in a market where most companies are working with a dozen or fewer. Forty years in the trade is the claim, and unlike a licence issue date there is no state record that either confirms or contradicts a founding year here, so treat it as a claim.

The practical caveat is geography. Carver is deep on the South Shore. If you are building in Newton, ask directly how they staff a job that far north and what it does to the schedule.

If you want the ADU to look like it was always there, Hawthorn is the one I would call in Greater Boston. They come from custom homes rather than from the ADU boom, and in Needham, Newton and Wellesley that pedigree is what most clients are actually buying.

Both credentials verify. HIC 166224 is active, renewed in July 2026 and running to July 2028, and the responsible person on it, Mathew Roth, holds CSL CS-103005, active and unrestricted. Google reads 5.0 across 20 reviews.

One thing to have straight before you sign, and it is the recurring Massachusetts trap. The brand name has no registration. Search the HIC register for Hawthorn Builders and you get four other Hawthorne businesses, three of them expired, and not the company you are looking for. The registrant is Hawthorn Investments LLC. That is not evasive, it is just how HIC works, but the entity on your contract should match the entity on the registration and you should check that yourself.

On price, they publish nothing and I would not expect them to. Premium custom work in these towns has an enormous spread. What to ask for instead is a fixed-price contract with a named allowance schedule, so you know which numbers are real and which are placeholders.

Walczak is the North Shore answer, and it is the verification I would point at if I wanted to show someone what a clean Massachusetts check looks like. HIC 185455, active, renewed June 2026 and good to June 2028, registered at an Ipswich address. Responsible person Derek Walczak, holding CSL CS-108993, active and unrestricted. The name on the registration and the name on the licence are the same person, which sounds obvious and is genuinely not guaranteed here.

What I like operationally is the standard-layouts option. A design a builder has already built and already had through a plan check moves faster than a bespoke one, and on the North Shore, where you are often dealing with older lots and tighter setbacks, that predictability is worth money. Custom is available if you need it; the point is you get to choose.

Two honest gaps. Twenty Google reviews at 4.8 is a real signal but a small one, and Google files them as a remodeler, so how much of that base is ADU work is unclear. And I could not verify a working website, which for a company this well registered is a strange gap. Ask for three recent addresses in your town and go look at them.

Conversions are the underrated route to a Massachusetts ADU, and FiveTen is the one on this page built around them. Basements, garages, interior reconfigurations. It is harder work than dropping a new structure on a clear part of the lot, because you inherit whatever the last four owners did, and it is usually cheaper, because the shell already exists.

Both credentials verify. HIC 191572, active, effective April 2025 to April 2027. Responsible person Alison H Loiselle, holding CSL CS-112264, active and unrestricted. Google reads 5.0 across 18 reviews.

Two entity details to check rather than assume, and both are the ordinary Massachusetts kind rather than anything alarming. The registrant is FiveTen Properties, LLC, which is not the FiveTen Construction & Design name on the marketing. And the registration carries a Woburn physical address with a Medford mailing address. Neither is a problem. Both are worth a question, because the name on your contract should be the name carrying the registration.

If you are weighing a conversion against a new detached build, the thing to ask them for is a written scope on the discovery risks: what happens if the foundation is not what everyone assumed, who decides, and who pays.

Western Massachusetts is thin on ADU builders and Backyard ADUs is the one genuinely working it, with modular units in the 525 to 1,000 square foot range and a set of design-path templates that take some time out of the front end.

The HIC registration 203349 is verified active, effective October 2025 and running to October 2027. Two things about it are worth your attention rather than mine.

First, the address. Both the mailing and physical addresses on the registration are 247 Coombs Rd, Brunswick, Maine. Holding a valid Massachusetts HIC from out of state is entirely legitimate and plenty of Connecticut River valley businesses work both sides of a border. It does mean your builder is a Maine company, and that is worth knowing before you plan around site visits.

Second, and this is why I have flagged rather than resolved it. The responsible person on the registration is named as Chris Lee, and the Massachusetts CSL register returns two active Christopher Lees with nothing to distinguish them, no address and no business linkage. Both are active, so whichever one it is, the licence is current. I could not confirm which, and I would rather tell you that than pick one and present it as verified. Ask them for the CSL number directly. It takes one email and it closes the only open question on this entry.