Accessory Dwelling Units

In December 2024, Town Meeting adopted an Accessory Dwelling Unit (ADU) policy in its Zoning Bylaw (Section 7.5), allowing attached or detached units of no more than 900 square feet as a matter of right in the R-1a, R-1b, RA, and R-2 Zoning Districts.

Middleton’s ADU Zoning Bylaw conforms to changes in Massachusetts’ Accessory Dwelling Unit zoning provisions, which were enacted as part of the Affordable Homes Act (Chapter 150 of the Acts of 2024), and which will take effect on February 2, 2025. For more information, please visit please visit https://www.mass.gov/info-details/accessory-dwelling-units.

If you are considering an ADU on your property, please review the FAQs below and contact the Building Commissioner or Planning Director for guidance.

FAQ

What is an Accessory Dwelling Unit (ADU)?

An Accessory Dwelling Unit (“ADU”) is an attached or detached Dwelling Unit that is accessory to a principal single-family Dwelling Unit and is otherwise defined in accordance with the provisions of G.L. c. 40A, §1A, as may be amended.

Where are ADUs allowed?

ADUs are allowed by right in all residential districts: R-1a, R-1b, RA, and R-2. ADUs are prohibited in all other districts. ADUs are subject to the requirements of Town of Middleton Zoning By-Law Chapter 235 Section 7.5, including Zoning Board of Appeals Site Plan Approval.

What size ADU is allowed?

An ADU may be no larger in gross floor area than one half of the gross floor area of the principal Dwelling Unit on the property or 900 square feet, whichever is less.

Can I put more than one ADU on my property? 

Only one ADU is allowed as a matter of right on any property. Additional ADUs require a Use Variance from the ZBA.

Do ADUs need to be attached to the principal structure?

ADUs can be attached or detached units. This means an ADU can be added to an existing home or constructed in a separate structure on the same lot. A detached unit could be a new building, or conversion of an existing building, such as a garage.

Can an ADU be sold separately?

An ADU cannot be owned separately from the principal dwelling unit.

Can I rent an ADU? 

ADUs may not be used as Short-Term Rentals or otherwise rented for a period shorter than thirty-one consecutive (31) days.

What do I need to know before converting or constructing an ADU?

Anyone who intends to convert an existing space or construct a new ADU will need Site Plan Approval before applying for a Building Permit. Please apply for Site Plan Approval according to the Zoning Board of Appeals application process as outlined on the ZBA website. Your application should include the following:

Required Submission Documents

  • Completed ZBA General Application
  • Completed Form A1. Site Plan Review
  • Certified Plot Plan showing the proposed ADU
  • Architectural Plans (Floor Plans and Elevations)
  • Abutters List (Assessors Office) & 2 Sets of Stamped & Addressed Envelopes
  • Copy of the Deed & Letter of Authorization (If applicant is not the owner)

Depending on the existing parcel and proposed changes, you may be required to apply for a Special Permit in addition to Site Plan Approval.

Where can I find additional information about ADUs?

For all requirements, read the draft Zoning Bylaw as approved at Town Meeting on December 12, 2024. This Bylaw will be added to the Middleton Zoning Code upon final approval by the Office of the Attorney General. 

If you are considering an ADU, please contact the Building Commissioner or Planning Director for guidance.