Planning an ADU in Massachusetts? Here’s What You Need to Know
See the incredible potential of your unfinished basement! This demonstrates how a professional basement finish can create a stunning, income-generating ADU.
Accessory Dwelling Units (ADUs) are becoming an increasingly popular option for homeowners in Massachusetts looking to expand their living space, accommodate multigenerational families, or generate rental income. Therefore, due to recent changes in state regulations and rising interest in compact, functional living, now is the time to explore whether an ADU is right for your property.
In this article, we’ll cover:
- Average cost to build an ADU in MA
- Important permitting considerations
- Why working with an experienced contractor matters
Average Accessory Dwelling Unit Cost in Massachusetts
Building an Accessory Dwelling Unit in Massachusetts varies significantly based on design, site conditions, and finishes. Here’s what current data shows:
- Standard Construction: $250–$325 per sq ft
- High-Performance: $350–$500+ per sq ft
For a 900 sq ft ADU, homeowners can expect to pay between $250,000 and $450,000. This estimate includes structural work, plumbing, electrical, and finished materials.
Permitting: What to Watch Out For
Massachusetts passed a new law in 2023 (effective February 2024) requiring all cities and towns to allow at least one ADU by right on single-family lots. However, each municipality may add its own rules and processes.
([Source: mass.gov – ADU Legislation News])
If you’re in the City of Boston, here’s what you need to consider:
- Permit Application: Submit your plans to the Boston Inspectional Services Department (ISD).
- Additional Permits: Depending on the scope, you may need plumbing, electrical, HVAC, or fire protection permits.
- Zoning & Design Guidelines: Requirements vary by neighborhood, so consult local zoning rules before starting.
([Source: City of Boston – ADU Guide])
Massachusetts ADU Code Requirement
Code of Massachusetts Regulations (CMR): As of February 14, 2025, the state of Massachusetts adopted 225 CMR 22.0, a set of energy-efficiency codes (the Stretch Energy Code) designed to make low-rise residential properties more energy-efficient
([Source: Mass.gov – 225 CMR 22.])
Why You Should Work with an Experienced ADU Contractor
Building an ADU is more complex than a typical home remodel. From navigating permits to integrating utilities, the process requires careful coordination and expertise.
Here’s why hiring a qualified ADU contractor is critical:
- Code Compliance: Professionals stay up to date on local building codes to ensure your ADU is fully compliant with city and state regulations
- Permit Management: A seasoned team will handle applications, inspections, and scheduling with city departments.
- Design-Build Expertise: ADUs require efficient use of space—experienced contractors help maximize livability without blowing your budget.
- End-to-End Service: From concept to completion, a reliable contractor streamlines the process and saves you time.
Thinking About an ADU? Let’s Talk.
At Sordan Construction, we specialize in full-service ADU design and construction across Greater Boston. Indeed, whether you’re planning a backyard cottage for your aging parents or a modern income-producing unit, we offer custom solutions that match your goals and your lot.
👉 Contact us for a free consultation and explore what’s possible on your property.
