Close enough for Sunday dinner. Independent enough to feel like home.
Most of the ADUs we build are generational — a place for a parent on their own to live next door. Private, single-level, built for the way your family actually lives.
The law finally caught up with the need
As of February 2025, Massachusetts allows accessory dwelling units up to 900 square feet by right in most single-family zones — no special permit fight, no town meeting. (Town-specific requirements still apply; we handle the permitting and know what each of our towns expects.)
That changed everything for families who’d been putting this off. A parent keeps their independence and their own front door; you keep them close. And when the time comes, the space flexes — guest house, home office, or rental income in a market that needs it.
Detached Cottages
A small home of its own in the yard — the classic generational setup, with full kitchen, bath, and laundry.
Garage Conversions
The structure’s already there. We convert and connect it — insulation, systems, and finishes to full-home standard.
Attached Suites
An addition with its own entrance — closest connection, easiest care, still separate front doors.
Approved Feasibility Study Provider
Before you spend a dollar, find out if it fits
Southcoast Building LLC performs Accessory Dwelling Unit (ADU) Feasibility Studies under the Massachusetts Housing Partnership (MHP) Accessory Dwelling Unit Incentive Program. We walk your property, check your zoning and utilities, and tell you whether an ADU works here and what it would realistically cost.
Providers are permitted to charge property owners up to $500 for a study. Southcoast Building LLC charges $0.
$0
Your cost for a Feasibility Study.
No obligation to build with us.
A Feasibility Study is not a design, a permit, or a construction contract. Building an ADU is a separate agreement with Southcoast Building LLC, and choosing a contractor is entirely the property owner’s decision. Southcoast Building LLC does not charge the additional $500 referred to below. Your cost is $0.
As a participating Feasibility Study Provider (Provider) in the MHP Accessory Dwelling Unit Incentive Program, we provide property owners with Feasibility Studies and are paid $500 for each completed study by the program. Providers may charge property owners up to an additional $500 for the Feasibility Study. Feasibility Studies help property owners understand the considerations in building an accessory dwelling unit on their property. Other services beyond Feasibility Studies may be offered for which contractor selection is solely at the property owner’s discretion.
The MHP Accessory Dwelling Unit Incentive Program is a statewide initiative administered by the Massachusetts Housing Partnership, in collaboration with and on behalf of the Executive Office of Housing and Livable Communities. Eligibility, restrictions, and offers are subject to change or cancellation. Please visit mhp.net/ADU for full details.
Typically a 4–5 month project
From design and permit to move-in, a typical SCB ADU runs four to five months. We handle design, permitting, and construction — single-level living, accessibility options (zero-step entries, wider doors, curbless showers) built in from the start, not retrofitted later.
Considering something bigger? See the Family Compound at 11 Walnut & Julia Lane — the same multigenerational idea, at neighborhood scale.
Case Study
See one we finished, priced line by line.
32 B Drive in Westport — a 900 sq ft, one-bedroom ADU built on the second story of an existing two-car garage. The case study carries every division of work, the full cost breakdown, the allowances we wrote into the contract, the one change order and what caused it, and the week-by-week schedule from permit to certificate of occupancy.
Twenty weeks, permit to final. One change order at 2.7% of contract, no schedule extension. Nothing ran over its allowance. The garage stayed a garage and the yard never changed.
Read the price honestly
That project delivered at $355,920 — but it is not a bare ADU price. It carries an 18′×18′ mudroom addition, a new 200 amp service for the whole property, a new boiler and water heater, and central AC added to the existing house. A stand-alone ADU of that size is a materially smaller number. The full breakdown is in the case study.
Company Profile
Who you are hiring.
Licenses and insurance, the trades we self-perform, and our ADU track record — feasibility through certificate of occupancy. Take the full profile with you.
Have a project in mind?
Tell us what you’re planning. We take on a limited number of projects each year, starting at $200,000 — and we’ll tell you honestly whether we’re the right builder for yours.