Frequently Asked Questions

1. What is an Accessory Dwelling Unit (ADU)?

An ADU is a smaller, self-contained residential unit located on the same lot as a single-family home. It can be detached (a backyard cottage), attached (a home addition), or internal (like a finished basement or garage conversion).

2. Are ADUs legal in my town?

It depends. Each city or town in Massachusetts has its own zoning bylaws that determine whether ADUs are allowed, and under what conditions. Mass ADU can help you determine what’s possible through a Feasibility Study.

3. Do I need a permit to build an ADU?

Yes. You’ll need to go through your local building department to obtain the proper permits. This may include zoning review, building, electrical, and plumbing permits. In some towns, special permits or public hearings may be required.

4. What are the size restrictions for an ADU?

Size limits vary by town, but most municipalities cap ADUs at around 600–900 square feet or a percentage of the primary home’s size (typically 30–50%). Mass ADU can help you figure out your town’s requirements.

5. How much does it cost to build an ADU?

Construction costs can vary significantly depending on the type, size, design, and site conditions. In Massachusetts, costs typically range from $250,000 to $350,000+. Our team provides clear pricing options with Good-Better-Best packages to match your budget and goals.

6. Can I rent out my ADU?

Many towns allow ADUs to be rented out, but some have restrictions (like requiring owner occupancy or long-term leases). We’ll help you navigate your town’s rental regulations during the planning process.

7. Will an ADU increase my property value?

Yes—when designed and built properly, ADUs can add significant value to your home by increasing livable square footage and offering rental income potential.

8. Can I build an ADU for my parents or adult children?

Absolutely. ADUs are a popular solution for multigenerational living—allowing privacy and independence while keeping loved ones close.

9. How long does the whole process take?

From initial consultation to move-in ready, the process typically takes 6–12 months, depending on design, permitting, and construction timelines.

10. What’s the first step if I’m interested in building an ADU?

Start with a Feasibility Study. This helps you understand what’s possible on your property, including zoning, utilities, site layout, and estimated costs—so you can make informed decisions before you design.