Accessory dwelling unit construction cost

Looking for accessory dwelling unit construction 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

The cost to build an ADU depends on factors like your foundation type, utility connection distances, interior finish choices, and whether you are doing a detached build or a garage conversion. We provide an exact pricing confirmed free on the call.

Frequently asked in Boston

What are the disadvantages of ADUs in Boston?

Potential disadvantages can include initial construction costs and the time it takes to secure permits, which can be complex in Boston. You might also consider the impact on your existing yard space or privacy. However, the long-term benefits often outweigh these concerns for many homeowners.

How much does an ADU cost in Massachusetts?

What are the rules for ADUs in Boston?

Boston has specific zoning ordinances and building codes that govern ADU construction. These rules dictate lot coverage, setbacks, and the maximum number of units allowed. The pros we work with are well-versed in these regulations and can guide you through compliance.

Is an ADU allowed in Maryland?

While this service focuses on Boston, Massachusetts, ADU regulations differ by state and municipality. Maryland has its own set of rules, and local jurisdictions within Maryland will have specific requirements. Always check with your local planning department.

Massachusetts and other states may have different incentive programs or financing options available. We can help you explore potential funding avenues relevant to your project.

How much does ADU construction cost?

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, Charlestown, Jamaica Plain — and every surrounding area.