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Accessory dwelling unit construction cost — Boston, MA

Looking for accessory dwelling unit construction cost in Boston, MA? Call AccessoryDwellingUnit Experts 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 is a major project, and the final bill depends on a few key things. Site prep is a big factor; if your land is sloped or needs extensive utility connections, costs go up. The materials you choose—from siding to kitchen finishes—also change the math significantly. Whether you’re building a detached unit or converting an existing garage shifts the permit requirements and structural work needed. We provide exact pricing confirmed free on the call.

About this service

The cost to build an ADU varies based on whether you are converting an existing garage or building a new detached structure from the ground up. Factors like foundation work, utility extensions, high-end finishes, and site access all influence the final total. Exact pricing confirmed free on the call.

Frequently asked in Boston

What are the disadvantages of ADUs in Boston?

While ADUs offer many benefits, potential disadvantages in Boston can include upfront construction costs and the time it takes to navigate city permits. You'll also need to consider ongoing maintenance and potential impacts on your existing property's utility usage. Discussing these with experienced local pros can help you weigh the pros and cons for your specific situation.

How much does an ADU cost in Massachusetts?
What are the rules for ADUs in California?

California has state-level ADU laws designed to streamline approvals, but local ordinances can still apply. These rules often cover minimum lot sizes, setback requirements, and parking. While we focus on Massachusetts, understanding how different states approach ADUs can highlight important considerations for any homeowner.

Is an ADU allowed in Maryland?

Yes, ADUs are permitted in many areas of Maryland, with specific regulations varying by county and municipality. Similar to Massachusetts, local zoning laws dictate size, placement, and other requirements. Getting informed about your local jurisdiction's rules is always the first step in planning an ADU.

What are the rules for ADUs in California?

California's ADU laws aim to encourage their development by setting clear guidelines on size, height, and owner occupancy. Local governments still have some authority to implement specific requirements. Understanding these state and local nuances is crucial for any ADU project in California.

California has offered various grant programs to help offset ADU construction costs, with specific amounts and eligibility criteria changing over time. These grants are intended to make ADUs more accessible. While this program is specific to California, it shows the potential for financial assistance in some regions.

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, Beacon Hill, Charlestown, Dorchester, Fenway-Kenmore, Jamaica Plain — and every surrounding area.

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