Accessory dwelling unit cost — Boston, MA | AccessoryDwellingUnit Services

Looking for accessory dwelling unit cost in Boston, MA? Call AccessoryDwellingUnit Services for a contact a provider — no obligation. Licensed adu builders serve Boston and the surrounding area, and you'll get straight answers on timing and what affects the price.

Last updated: September 24, 2026

What affects the price

Building an ADU involves several moving parts that shape your total investment. The final figure depends heavily on whether you choose a prefab unit or a custom build from the ground up. Site conditions are another major factor; if your property requires extensive grading, utility trenching, or foundation work, costs will climb. You also have to consider your choice of finishes, like high-end appliances or custom cabinetry. Navigating local permit fees and impact assessments also adds to the total.

About this service

Total costs for an ADU vary based on the size of the unit, the complexity of the site, and the quality of materials you select for the kitchen and bathroom. Things like trenching for new sewer lines or upgrading your main electrical panel can also impact the bottom line. We provide an exact pricing confirmed free on the call.

Frequently asked in Boston

What are the disadvantages of ADUs in Boston?

In Boston, potential disadvantages can include the initial construction cost and the time it takes to get permits. You'll also need to consider how an ADU might affect your property taxes. It's important to weigh these factors against the benefits of added space and potential income. Discussing these with a pro can clarify any concerns.

How much does an ADU cost in Massachusetts?

What are the rules for ADUs in Massachusetts?

Massachusetts has specific regulations for ADUs, often focusing on lot size, setbacks, and utility connections. Local zoning bylaws in Boston can also add layers of requirements. Understanding these rules is key before you start planning your build. The pros we work with are familiar with these state and local guidelines.

Is an ADU allowed in Maryland?

This page is about Boston, Massachusetts. While Maryland has its own ADU laws, we focus on serving homeowners in the Boston area. For information specific to Maryland, you would need to consult a local service provider there. We're here to help with your Boston ADU needs.

What are the rules for ADUs in California?

This page is about Boston, Massachusetts. California has a distinct set of ADU regulations that differ significantly from Massachusetts. If you are in California, you'll need to seek out ADU services specific to that state. We are focused on providing ADU services here in Boston.

This page is about Boston, Massachusetts, and does not cover California grants. We focus on providing ADU services and estimates for homeowners in the Boston area.

Also serving nearby: Quincy · Cambridge · Lynn · Newton · Brockton

All cities in Massachusetts →

More on this: HUD ADU resources — ADU policy and financing research.

Service area details

653,833residents

13,525per sq mile

8ZIP codes served

Serving all of Boston — population 653,833; about 13,525 residents per square mile across 48.3 sq mi. ZIP codes covered include 02108, 02109, 02110, 02111, 02112, 02113, 02114, 02115.

Neighborhoods served in Boston: Back Bay, South End, Beacon Hill, North End, Allston, Jamaica Plain — and every surrounding area.