Granby, MA

Granby, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: N/A

What you need to know: 

Granby does not allow attached or detached accessory dwelling units (ADUs). The town also specifically prohibits the conversion of single family homes into duplexes or mutli-family homes.

See the full text here: Zoning Ordinance

Huntington, MA

Huntington, Massachusetts’ Accessory Dwelling Unit (ADU) Rule

City Acceptance Rating: N/A

What you need to know: 

Huntington does not allow detached accessory dwelling units (ADUs). Granny flats must be constructed within existing space or as an addition.

See the full text here: Zoning Ordinance, Section: Accessory Family Dwelling Units

Hatfield, MA

Hatfield, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: N/A (10 is most accepting)

What you need to know: 

Hatfield does not allow detached accessory dwelling units (ADUs). Granny flats must be constructed within existing space or as an addition.

See the full text here: Zoning Ordinance Article 23 Accessory Apartments

Hadley, MA

Hadley, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: N/A

What you need to know: 

Hadley does not allow detached accessory dwelling units (ADUs). Granny flats must be constructed within existing space or as an addition.

See the full text here: Zoning Ordinance SECTION XXVI Accessory Apartments

Greenfield, MA

Greenfield, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 10/10 (10 is most accepting)



What you need to know: 

Greenfield revised its rules for Accessory Dwelling Units in 2020 to make it EXTREMELY easy for homeowners to add an additional dwelling unit to their properties. The city sees ADUs as a great to way increase density and create high quality housing without sacrificing the character of the town. Since the bylaw was approved, there have been many ADUs added to homes including at least one backyard home (detached ADU)!

ADUs can be added to two and single-family homes by right! This means there is no public hearing process and owners of two-family homes with landlord experience can add another unit.

Type of Permit Required:

Greenfield allows all types of ADUs by right. This included space conversion, detached ADUs, additions, and conversion of existing accessory structures (barns, garages, etc).

ADU Rules in Greenfield:

• The additional unit must have its own kitchen, bathroom, and means of egress.

• An ADU can be added to single-family and two-family properties.

• One of the two dwellings must be owner-occupied.

• The single-family character of the home must be retained and new entrances must be located on the side or rear of the house.

• New detached structures or additions must match the character of the existing house.

• Any stairways, access, or egress alterations serving the Accessory Dwelling Unit shall be hidden from public view.

• The ADU can not be larger than 900 sq. ft. or one-third the total gross floor area of the home, whichever is greater.

• Once built, the ADU cannot be enlarged beyond the square footage approved with the original permit.

• An Accessory Dwelling Unit may not be occupied by more than three (3) people.

• The ADU must have 2 or fewer bedrooms.

• Detached ADUs are considered Accessory Structures and must follow rules as such.

• The entire property must have at minimum 2 parking places and cannot have more than 4.

• Septic system capacity must be validated by the Board of Health before a permit issued.

• Deviations from the above can be granted to accommodate people with a disability and persons with limited mobility.

See the full text here: Zoning Ordinance Section 200-7.18. Accessory Dwelling Units, page 119

ADU Bylaw

Dimensional Requirements

Great Barrington, MA

Great Barrington, MA Accessory Dwelling Units (ADU) Rules

City Acceptance Rating: 7/10 (10 is the most accepting)

What you need to know: 

Great Barrington loves ADUs and allows them by right in all zoning districts. However, it is important to note that the backyard home cannot be greater than 900 SF. Additionally, if an ADU is proposed in an existing nonconforming structure, a special permit will be needed.

Great Barrington also defines a path to convert a single family property to a legal duplex or multifamily property. For eligible lots, this formal conversion will allow homeowners to maximize their property value. Duplexes and multifamily properties are discussed in section 8.1 and 8.3 of the zoning bylaw.

The town is also deliberating on new rules that would allow tiny homes on trailers! Stay tuned for more information and if you are a resident of Great Barrington contact the planning/zoning board to voice your support.

Type of Permit Required:

Great Barrington allows both attached and detached accessory dwelling units (ADUs) to be built by right.

If the ADU is proposed in a nonconforming lot, it requires a special permit.

ADU Rules in Great Barrington:

• Only one ADU is allowed per lot.

• ADUs are allowed on single family and two family lots.

• The ADU and primary home must have the same owner.

• The ADU cannot be larger than 900 gross square feet. (“Gross” includes unfinished space and area with low ceilings)

• A newly constructed backyard home or addition must meet setback and other dimensional requirements related to the primary home. An ADU can be located in an existing nonconforming structure with a special permit.

• The ADU must be provided one parking space. This spot must be in addition to the minimum required spaces for the primary home. The parking space must be located behind the front setback line, unless a variance is granted by the planning board.

• When possible, new entrances to the ADU must be located on the rear or side of the building.

• Fire escapes and outside stairways leading to a second or higher story shall be located on the rear or side of the building. They should not be visible from the street.

Read the full bylaws here:

Zoning Ordinance, Section 8.2 Accessory Dwelling Units

Zoning Ordinance, Section 8.1 Two-family residential use of a single lot.

Zoning Ordinance, Section 8.1 Multifamily dwellings

Deerfield, MA

Deerfield, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: N/A

What you need to know: 

Deerfield does not allow detached accessory dwelling units (ADUs). The town allows attached accessory dwelling units under extremely strict circumstances. ADUs can only be used to provide in home care for someone who needs help with Activities of Daily Living and the Special Permit issued has to be renewed every 5 years.

See the full text here: Zoning Ordinance

Belchertown, MA

Belchertown, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating:

N/A

What you need to know: 

Belchertown does not allow detached accessory dwelling units (ADUs). Granny flats must be constructed within existing space or as an addition.

See the full text here: Zoning Ordinance Section 145-29.1 Accessory Apartments

Amherst, MA

Amherst, Massachusetts Accessory Dwelling Unit (ADU) Rules

Updated: 12/05/2025

What you need to know: 

Amherst, like all of Massachusetts since the passage of the 2024 Affordable Homes Act, allows ADUs by right. Each town has slightly different rules surrounding ADUs, but they all must adhere to the framework outlined by the state. 

There are two types of ADUs allowed in Amherst - Protected Use ADUs (PADU) and Local ADUs. PADUs are generally in line with Massachusetts state law regarding ADU zoning and requirements, while Local ADUs have their own rules.

Type of Permit Required:

Protected Use ADUs in Amherst are considered by-right, meaning they are allowed in any single-family residential zoning district with a simple building permit. 

Local ADUs require administrative approval if the lot has no existing PADU. If the lot already has a PADU, owners can apply for a special permit to build a Local ADU.

ADU Rules in Amherst:

General ADU Rules in Amherst:

• No more than one Local ADU and one Protected Use ADU are allowed on the same lot as the main house.

• ADUs can be attached, detached, or built within the main house.

• Whenever possible, detached ADUs cannot be built closer to the road than the main house.

• ADUs need to submit a parking plan to the Building Commissioner and have it approved. 

• The driveway can be altered or added to, but a new driveway to the street is not typically allowed.

• No more than two off-street parking spaces can be added for any ADU.

• ADUs must have a separate entrance from the main house - attached ADUs can share an entry hall with the main house, but need a separate entry within the entry hall. 

• Storage of trash and recycling must be inside the interior of the ADU, in a garage or another accessory outbuilding. 

• All exterior lighting must be designed and installed to avoid disturbing neighboring properties.

• If the owner wants to rent the ADU or their main house, it will have to be registered and permitted in accordance with the Residential Rental Property Bylaw (See here: https://www.amherstma.gov/DocumentCenter/View/24029/Residential-Rental-Property-Bylaw?bidId=).

• ADUs shall not have a new driveway or curb cut unless approved by public works.

Protected Use ADU Rules in Amherst:

• PADUs can be maximum 900 square feet, or half the Gross Floor Area of the main house; whichever is smaller. 

• There is no minimum lot size to build a PADU.

• PADUs within ½ mile of a transit station do not require additional parking. Properties outside of that area could require additional off-street parking. 

• PADUs do not require owner-occupancy.

• PADUs have less restrictive setback requirements than Local ADUs in Amherst.

Local ADU Rules in Amherst:

• Local ADUs can be a maximum of 1200 square feet.

• Local ADUs must have a similar architectural style as the main house.

• Either the main house or the Local ADU must be occupied by the property owner(s).

Resources:

https://www.amherstma.gov/DocumentCenter/View/82436/8b-voted-cca--CRC-ADU-Amend-Both-9-11-2025-1?bidId=

Northampton, MA

Northampton, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 10/10 (10 is most accepting)

Last updated: 7.22.2024

Source: City of Northampton

What You Need To Know

Northampton updated their ADU rules to allow for two single-family dwellings on one parcel in residential districts.  In Northampton, they have removed ADU language from their rules and permit everything as a second dwelling on the same lot. Each district has specific requirements that must be met for the new dwelling unit.

Type of ADU Permit Required

Each additional single family dwelling (ADU) is subject to site plan approval by the planning board. 

ADU Rules

• Two single-family dwellings are allowed subject to site plan approval in the follow districts:

  • Rural Residential

  • Suburban Residential

  • Urban Residence A

  • Urban Residence B

  • Urban Residence C

  • Water Supply Protection

  • Farms Forest Rivers

  Each zoning district has a specific lot area, open space, setback, and parking requirements for adding single family dwellings to a piece of land with an existing single family residence.  Please connect with our team to see what is possible at your specific address!
  
  
  

Resources:

https://ecode360.com/13265306

Chesterfield, MA

Chesterfield, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 7/10 (10 is most accepting)

What you need to know: 

Chesterfield joined many cities in MA by revising its zoning bylaw to make it easier for homeowners to build accessory apartments in most zoning districts. 

Type of Permit Required:

Conversion of Existing Space or Attached:

By right in:

• Town Center

• Agricultural Residential I

• Agricultural Residential II

By Special Permit in the following overlay districts:

• Floodplain

• Westfield River Protection District

• Water Supply Protection District

Special permits are also required if an apartment is being added to a commercial building.

Detached ADUs:

A Special Permit is always required for detached ADUs.

ADU Rules in Chesterfield:

• The ADU must be a fully separate dwelling unit with its own kitchen, bath, and egress.

• A lot can only have one accessory apartment.

• The ADU must have 2 or fewer bedrooms.

• At least two additional off-street parking spaces shall be provided for the ADU. Parking spaces shall be located on the side or rear of the building to the extent feasible.

• The ADU’s appearance must match the character of the original building.

• New entrances shall be located on the side or rear of the building to the extent feasible.

• The ADU must be subordinate to the primary building.

• The living area shall not be more than 33% of the existing residential living space (commercial building SF) or 800 square feet, whichever is less.

• Small homes or commercial buildings, can bypass the 33% limitation and build a 300 square feet ADU.

Read the full bylaw here: Zoning Ordinance, Section 6.1 Accessory Apartments

Easthampton, MA

Easthampton, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 9/10 (10 is most accepting)

What you need to know: 

In 2021, Easthampton revised its zoning bylaw to allow homeowners to build accessory apartments in all zoning districts.

Type of ADU Permit Required:

A building permit is required and a special permit in some instances (we can help with this).

ADU Rules in Easthampton:

• ADUs are allowed on lots with Single-Family or Two-Family Homes.

• The owner(s) of the detached single- or two-family dwelling must occupy one of the units as their primary residence at the time of occupancy. (No longer in compliance with the MA state ADU law)

• A new detached ADU (and/or an attached unit consisting of new construction) must not exceed 900 square feet.

• One new off-street parking space is required for the ADU. The new parking space materials must be consistent with the existing driveway.

  • A waiver of this requirement may be granted for such reasons as, the resident has a disability or an occupant that does not own a vehicle.

• If a new or expanded driveway is proposed within 10 feet of a side or rear lot line, a landscaped buffer of at least six feet—measured from the lot line—must be provided.

  • Within this buffer zone, no parking, storage, or other use is permitted unless a written agreement is created and submitted to the building department between the applicant and neighbor.

• No more than one ADU on a lot.

• The principal dwelling and the ADU must remain in common or single ownership.

• For tax purposes, a second dwelling unit may be considered a two-family dwelling for tax purposes.

Interior and Attached ADU Rules

• An interior or attached ADU is required to be designed to maintain the appearance of a single- or two-family dwelling with a separate entrance.

• The separate entrance must be either outside or through a shared entry with the primary dwelling.

• All stairways to the ADU above the first floor must be within the building. If constructed outside the building, the stairs cannot face the street.

• Maximum height, minimum setbacks, and maximum building coverage for a primary dwelling must be met.

Detached ADU Rules

• An existing accessory structure can be converted to an ADU as long as no changes in footprint or height are made.

• Maximum height, minimum setbacks, and maximum building coverage for a primary dwelling must be met.

• A new detached ADU cannot be greater than 900 square feet.

Easthampton Setbacks and Density Tables

See the full text here: Zoning Ordinance Section 8.5, Accessory Apartments, page 117