Accessory Dwelling Unit (ADU) Zoning Bylaw - Draft Amendments for 2022 Special Town Meeting

***UPDATE: This bylaw amendment passed Town Meeting October 2022 and was approved by the Attorney General's Office in January 2023***

PB 2221 ZNG: Updates to Section 3.3 of the Zoning Bylaw, Accessory Dwelling Units (Special Town Meeting October 17, 2022)

The Planning Board and Zoning Board of Appeals are co-sponsoring amendments to the Accessory Dwelling Unit (ADU) Section of the Zoning Bylaw for Special Town Meeting beginning October 17, 2022 at 7:00pm at Westford Academy.

ADUs are permitted in Westford by Special Permit from the Zoning Board of Appeals. The Board has approved an average of 5 ADUs per year since 2015. More than half of these applications also required variances related to dimensional standards.

What changes are proposed?

  • Allow for special permit transfer upon a change in ownership
    • Presently: upon change in ownership, the special permit that allowed creation of the ADU expires. This occurs even if the new owner is making no changes whatsoever to the ADU, and necessitates a new permitting process to continue to legally maintain it, which takes additional time and expense.
    • Proposed: Provided the new owner is not making changes to the ADU, the special permit remains in effect, so long as the new owner provides an affidavit stating they will not expand or alter the ADU. This could save the previous and/or new owner(s) a several month-long, costly permitting process.
  • Simplify the ADU standards by replacing area calculations currently based on a percentage of gross floor area, to a flat square footage allowance
    • Presently: The ADU cannot exceed 33% of the gross floor area of the principal structure, and cannot exceed a 15% increase in the size of the principal structure. These calculations can, at times, be confusing. They can also lead to a need for variances, which can take additional time and money for the permitting process, and has the risk of denial. For example, there have been instances in recent years where people proposing a 500 sq.ft. ADU (with a modest-sized home) have needed a variance for size, while people proposing a 1,000 sq.ft. ADU (with a large home) have not needed a variance.
    • Proposed: No percentage calculations - Instead, ADUs can be up to 900 sq.ft., not exceeding the size of the principal dwelling unit, or can be reasonably larger if the space is needed to install features that facilitate access and mobility for persons with disabilities. This would make it easier for people with modest-sized homes to have an ADU without needing variances for size, and provide a more level playing field for all residents wanting ADUs. Furthermore:
      • The latest Massachusetts legislation defines ADUs as being not greater than 900 sq.ft.
      • The average ADU size of approved ADUs in Westford since 2015 is 894 sq.ft.
  • Expand upon the purpose of the bylaw
    • A few purposes were added to better reflect what the ADU bylaw is for, such as protecting the single-family character of a neighborhood, encouraging more economic and energy-efficient use of the town's housing, and providing units for persons with disabilities.

The latest draft can be viewed at this link.

The Planning Board Report and Recommendation to Town Meeting can be found here.

Helpful Links

Massachusetts Smart Growth/ Smart Energy Toolkit Modules - Accessory Dwelling Units (ADUs)

Chapter 358 of the Acts of 2020: Full Text

If you have any questions or comments, please contact Assistant Planner Sierra Pelletier,, 978-692-5524