ADU Frequently Asked Questions

---

An Accessory Dwelling Unit (ADU) is a self-contained residential unit located on the same lot as a primary home. It can be attached (converted space or addition) or detached (separate structure, such as a backyard cottage)

Yes, ADUs are legal in many Massachusetts municipalities. Recent state legislation has encouraged towns and cities to relax zoning restrictions to allow ADUs "by right" or with a special permit.

ADU's can have a maximum of 900 square feet or be no larger than 50% of the gross floor area of the principal dwelling, whichever is smaller.

Yes, you will need a building permit for an ADU.

Yes! Under Massachusetts’ updated ADU laws, homeowners can rent out their ADUs without an owner-occupancy requirement. This means you do not have to live on the property to rent out either the primary home or the ADU. 

An ADU can increase your property value by adding livable space and creating an income-generating rental unit. It also makes a home more attractive to buyers looking for flexible living arrangements, such as housing for relatives or rental income opportunities.

The timeline varies depending on whether the ADU is new construction or a conversion. Generally:

• Attached ADUs or garage conversions: 3–6 months
• Detached ADUs (new construction): 6–12 months
  Factors like permitting, weather, and material availability can affect timelines.

Costs vary based on size, design, and materials, but typical estimates include:

• Attached ADUs or conversions: $75,000 – $150,000
• Detached ADUs: $150,000 – $300,000+
  Financing options include home equity loans, ADU-specific loan programs, or cash savings.

At Terra Development Group, we specialize in ADU design, permitting, and construction, ensuring a smooth, stress-free process. We handle everything from site assessment and compliance with local laws to custom design and high-quality construction—helping homeowners maximize their property's potential.

Ready to build your ADU? Contact us today for a consultation!