Newton, MA

Newton, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 10/10

Last Updated 6.20.2024

Image source: Kenneth C. Zirkel

What You Need To Know

In Newton, ADUs can be detached as well as within a primary dwelling.  The design requirements for each type of ADU are extensive, and getting approval for an ADU is a difficult process.

Type of ADU Permit Required

ADUs within a dwelling and detached dwellings both are by right in Newton; however, a special permit may be required/granted for the construction of spaces that exceed the baseline requirements.  

ADU Rules

Requirements for both ADUs within a dwelling and detached ADUs

  • The ADU must have the same owner as the primary dwelling.

  • Only one ADU is allowed per lot.

  • The owner of the property must reside in either the primary dwelling or the ADU.

  • The total number of individuals allowed on the lot is not increased by the addition of an ADU.  

  • ADUs can only be rented for a period of 30 days or more.

  • Additional parking is not required if an ADU is built, but if it is added, a screening process must be followed.

  • The property owner must provide documentation prior to a certificate of occupancy being granted to the county.  Documentation stating the ADU rules will be followed must be filed yearly as well.

Requirements for detached ADUs

  • Detached ADUs must be at least 250 square feet and cannot be greater than 900 square feet or 50% of the total habitable space of the existing dwelling, whichever is less.

    • A special permit may be granted to increase the square footage up to 1,500 square feet.

    • Habitable space is the total of the habitable space of the primary dwelling and the ADU.

  • The design of the ADU must align with the character and architecture of the primary residence.

  • The ADU must meet dwelling separation and setback requirements.

  • ADUs are included in the floor area ratio.

  • If the home is of historic significance and outside of a historic district, a detached ADU may be allowed by right without a special permit if the following conditions are met:

    • The detached ADU must be located within an accessory structure or primary dwelling.

    • The ADU must be greater than 15 feet from the existing dwelling.

    • Any alteration to the exterior of the building must preserve the character of the historic building.

Requirements for ADUs within a dwelling

  • ADUs within a dwelling must be at least 250 square feet and cannot be greater than 1,000 square feet or 33% of the total habitable space of the primary dwelling, whichever is less.

    • Habitable space is the total of the habitable space of the primary dwelling and the ADU.

    • A special permit may be granted up to 1,200 square feet or 40% of the total habitable space, whichever is less.

  • Any exterior alterations made to accommodate an ADU must be made in a way that maintains the original structure and look of the primary dwelling.  Specifically:

    • Siding, roof pitch, trim, and windows

    • Exterior staircases are permitted but should be designed to compliment the primary dwelling or hidden.

    • Only by special permit can new street side entrances be created.  

Resources: 

https://www.newtonma.gov/home/showpublisheddocument/29823/638457536861130000

Attached ADU, Convert Existing SpaceGuest UserGreater Boston, Friendliness score 10/10, Newton, Massachusetts