Backyard Garage to Two-Bedroom ADU
A masonry garage on a Somerville lot is being converted into a two-story, two-bedroom accessory dwelling unit — the existing shell kept, a full second story added, and the whole property’s utilities and fire systems brought up to support it.
The Opportunity
An underused masonry garage sits at the back of a Somerville lot. Under Massachusetts’ ADU-by-right rules, a structure like this can become legal, permitted living space — and that’s the plan: a full two-story, two-bedroom accessory dwelling unit, without tearing down what’s already there.
The Plan
We’re keeping the existing block shell and infilling the old overhead-door opening with a new framed wall, then building a full second story under a new pitched roof in Hardie siding with black windows. Inside: living and kitchen on the first floor, two bedrooms and a full bath above.
Where It Stands
The project is in permitting now, with two design directions still on the table. Alongside the structure, the scope covers all-new utilities, a main-house electrical service upgrade, a full ADU sprinkler system, and a fire panel upgrade — the infrastructure that makes an ADU livable and code-compliant.
A backyard garage, kept and reimagined.
Rather than demolish, we’re building on what’s there. The existing masonry garage gives the ADU a solid shell and foundation to work from — the former garage-door opening gets framed in, and a new second story rises above. It’s a faster, less wasteful path to a finished dwelling than starting from bare ground.
Two directions under consideration.
Design is still being finalized. Both schemes share the same footprint, roofline, and window layout — the difference is finish and palette. One leans modern, in charcoal board-and-batten with a natural cedar gable accent; the other stays traditional, in a warm cream with a shingled gable. Same structure, two ways to fit the neighborhood. These are design concepts, not photos of a finished build.
Built off real plans.
These aren’t napkin sketches. The ADU is moving through permitting on a full set of architectural drawings — elevations, fenestration schedules, fire-rated assemblies, and a two-floor layout designed around egress, mechanical space, and code. This is the part of an ADU most owners underestimate, and it’s where doing it right starts.
More than a garage conversion.
A livable ADU is as much about infrastructure as it is about framing. Here’s what the full scope covers:
- Existing masonry garage shell retained; former overhead-door opening infilled with a new framed wall
- Full second-story addition under a new pitched roof — Hardie siding, black windows
- 2 bed / 1.5 bath layout: living and kitchen below, two bedrooms and full bath above
- All-new utilities — water and sewer service
- Main-house electrical service upgraded to create capacity for the ADU
- Full fire sprinkler system in the ADU
- Fire alarm panel upgrade in the main house
- New patio build serving the ADU
- Additional site and livability improvements across the property
Thinking about an ADU?
Massachusetts now allows ADUs by right on most single-family lots. If you’ve got a garage, a backyard, or unused space, we’ll walk you through what’s actually possible — feasibility, permitting, utilities, and cost — before you commit to anything.
Start an ADU Conversation Or call (617) 410-6623