ADU Conversion Process in Greater Boston
Accessory Dwelling Units (ADUs) are having a moment in Greater Boston — and for good reason. A legal ADU can house family, generate rental income, or add flexible space without moving. But converting a basement, garage, or unused area into a compliant living unit takes planning, permits, and coordinated construction.
Here is what the process typically looks like for Massachusetts homeowners.
Step 1: Feasibility and local rules
Every municipality has its own zoning and building requirements. Before you invest in design, confirm whether an ADU is allowed on your lot, what size and occupancy limits apply, and whether separate utilities or entrances are required. A contractor familiar with local departments can help you interpret early constraints.
Step 2: Design and scope
Define how the unit will be used — long-term rental, family member, or home office with future flexibility. Layout affects ceiling height, egress windows, kitchen and bath placement, insulation, and HVAC. Smart planning upfront reduces expensive changes later.
Step 3: Permits and approvals
Most ADU projects require building permits and multiple inspections: framing, electrical, plumbing, insulation, and final certificate of occupancy. Your general contractor should coordinate submissions, schedule inspections, and keep work aligned with approved plans.
Step 4: Construction phases
A typical conversion includes:
- Demolition and structural adjustments
- Framing, insulation, and fire separation where required
- Rough plumbing, electrical, and HVAC
- Drywall, flooring, tile, and finish carpentry
- Fixtures, paint, and punch list
Urban properties in Somerville and Cambridge often involve tight access, noise considerations, and coordination with neighbors — another reason an experienced local team matters.
Step 5: Final inspection and occupancy
Passing final inspection is what makes the unit legal to occupy or rent. Cutting corners on code compliance creates problems at sale, refinance, or insurance review. Licensed work documented through permits protects your investment.
Is an ADU right for you?
ADUs are not one-size-fits-all. Construction cost, rental potential, and local rules all factor in. Start with a conversation about your property, goals, and budget.
The Solid Builder manages ADU conversions from framing through finishes across Peabody, Somerville, Cambridge, and the North Shore. View our ADU service page or request a consultation.