Lancaster, MA

Lancaster, Massachusetts’ Accessory Dwelling Unit (ADU) Rules

Last updated: 2024

Lancaster, MA Accessory Dwelling Unit (ADU) Rules

As of 4/22/2024

City Acceptance Rating:

5/10(10 is most accepting)

What you need to know about ADUs in Lancaster, MA:

ADUs have been possible in Lancaster under a special permit since 2007.  The town of Lancaster does not specify whether the ADU must be attached, detached, or retrofitted; however, they have specific requirements detailing the size, aesthetic, and desired purpose of the ADU.  

ADU permit requirements in Lancaster, NA:

A special permit is required for construction of ADUs in Lancaster.  

The ADU Rules in Lancaster, MA:

1. The primary residence must have been built five years prior to building an ADU.

2. Either the primary residence and ADU must be owner occupied.  Temporary absences are allowed for no more than 12 months.

3. The habitable size of the ADU is limited to ⅓ of the habitable square footage of the existing dwelling and the proposed ADU or 1,200 square feet, whichever is less. 

4. The ADU must have a separate entrance from the primary residence, there can be no more than one entrance door on a single side, and there cannot be any exterior staircases.

5. The ADU cannot be designed to house greater than three people

6. If not on town water and sewer, the owner must document that appropriate water and sewer modifications have been made to accommodate the needs of the ADU.

7. There must be at least three parking spaces available.

8. There must be a benefit to the community under the following conditions:

1. There is a benefit to a community housing need or special need of the planned occupant.

2. The compatibility of the design in relation to the existing structure and neighborhood.

3. The construction impact to natural resources, privacy of neighbors, overall character of the neighborhood, and safety.

Resources:

https://ecode360.com/11813694 (scroll to the bottom of the page.  Section G)

Updates:

https://www.ci.lancaster.ma.us/sites/g/files/vyhlif4586/f/pages/la2689-220a_use_regulation_schedule.pdf - Indicates that special permit is still required
https://ecode360.com/LA2689/laws/LF1884287.pdf  - indicates there may be a new (unclear) zone that would make ADUs by right or just retrofit.  Unclear to me (sam) at this time.

Medway, MA

Medway, Massachusetts’ Accessory Dwelling Unit (ADU) Rules

Last updated: 2019

What you need to know:

Medway, 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. The rules for Arlington are outlined below. 

Type of ADU permit required:

ADUs in Medway do not require special permits, and can be built using a traditional building permit. If you have a particularly tight lot, it may be possible to get a special permit to reduce your setbacks.

ADU Rules in Medway:

• Medway allows ADUs by right in single-family zoning districts.

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

• ADUs may be attached, detached, or built within the existing house.

• Short-term rentals of ADUs are not allowed.

• 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. 

• Properties within ½ mile of a transit station do not require additional parking. Properties outside of that area require one additional off-street parking spot for the ADU.  

• The main house and ADU must be owned by the same person(s). 

Resources:
https://storage.googleapis.com/juniper-media-library/117/2025/10/Zoning%20Bylaw%20Final%20-%20AG%20Approved.pdf (See PDF pages 130-131)

Medfield, MA

Medfield, MA Accessory Dwelling Unit (ADU) Rules

Last updated: 2004

Photo courtesy of Town of Medfield

The town of Medfield, MA had the following provisions for Accessory Dwelling Units:

1. A dwelling unit within a single structure for use by a family member

2. The house was in existence prior to 1938

3. The house has a minimum of 2000 sq. ft. of existing floor area

4. The house meets the lot area requirement for a one-family dwelling in its district

5. An addition to the house of up to 10% of the existing floor area must be allowed in the rear or side yard, provided the addition is architecturally consistent with the existing house

6. The exterior of the house must not be altered except for restoration consistent with the existing architecture and exits required by law, which exits must be in the rear or at the side of the house.

7. The accessory unit must have a minimum floor area of 500 sq. ft., plus 100 sq. ft. for each bedroom over one

8. The accessory unit must have a bathroom and a kitchen or kitchenette

9. One off street parking space must be provided for each bedroom in the accessory unit, in addition to spaces required for the existing dwelling

10. The owner of the house must occupy the house or the accessory unit, except for bona fide temporary absences of up to one year

11. The Special Permit must be a personal permit restricted to the individual owner-applicant and shall terminate when said owner-applicant ceases to own the dwelling

12. In the event of a change of ownership of a house for which a Special Permit has been issued for an accessory unit, the new owner or holder of a purchase and sale agreement with the owner may apply for a renewal of the Special Permit.

13. Special Permit will terminate upon the happening of any of the following events: (a) Sale of the property (b) Death of those persons occupying the Family Apartment, (c) Permanent change of domicile of all of the persons occupying the Family Apartment from said Family Apartment to some other location either within or without the Town of Medfield

Read more:

Williamsburg, MA

Williamsburg, MA Accessory Dwelling Unit (ADU) Rules

New Rules allowing Detached ADUs coming in September 2021!!!!

City Acceptance Rating:
N/A

What you need to know: 

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

Type of permit:

A special permit from the zoning board of appeals is required.

ADU rules in Williamsburg:

• The ADU must have its own kitchen and bath and be within an existing single family dwelling.

• One of the two units must be owner occupied.

• The ADU’s floor space must be less than 750 square feet or one-third of the existing living space whichever is greater.

• No more than three people can live in the ADU

• Parking must comply with parking requirements outlined in the parking section of the Bylaw.

Other Notes:

• Human habitation is not allowed in accessory structures, aka backyard homes.

• Multi-family and two-family homes are allowed in all zoning districts. This means homeowners can convert their homes from single to two family dwelling INSTEAD of adding an ADU.

See the full text here: Zoning Ordinance Section 9.1 Accessory Apartments

Wilbraham, MA

Wilbraham, MA Accessory Dwelling Units (ADU) Rules

City Acceptance Rating: N/A

What you need to know: 

Wilbraham 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 4.1 Accessory Apartments

Warwick, MA

Warwick, MA Accessory Dwelling Units (ADU) Rules

Updated: 11/17/2025 - Rules still being finalized

What you need to know:

Warwick, 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. The rules for Warwick are outlined below. 

Type of Permit Required:

ADUs in Warwick do not require special permits, and can be built using a traditional building permit. Residents are allowed to build one ADU per lot. 

ADU rules in Warwick:

• An ADU can be up to 900 square feet in Warwick. 

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

• Short-term rentals are allowed in either the main house or the ADU, but not both simultaneously.

• Properties with an ADU may require additional off-street parking (driveway or garage).

Resources:

https://warwickma.org/wp-content/uploads/2024/12/2024-12-09-STM-Minutes-Complete.pdf

https://warwickma.org/town-clerk/2024-12-09-special-town-meeting-minutes/?highlight=%5C%22accessory%20dwelling%20unit%5C%22

Sunderland, MA

Sunderland, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: N/A

What you need to know: 

Sunderland does not have a section in its bylaw covering accessory dwelling units (ADUs).

However, the town does allow two-family homes in all zoning districts except C-2. If your property has enough space you may be able to add backyard tiny home as a formal 2nd unit.

See the full text here: Zoning Ordinance

South Hadley, MA

South Hadley, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: N/A

What you need to know: 

South Hadley does not have a bylaw for detached accessory dwelling units (ADUs). However, they do provide a path to convert single-family homes into duplexes following the rules in the town’s zoning ordinance.

In order to convert a property, owners must get written permission from 3 of their neighbors and their property must meet meet minimum dimensional requirements.

The zoning bylaw does not specifically state whether a detached structure (backyard home) could act as the second unit.

If you are interested in building in South Hadley and would like more concrete information, contact our team. The rules in South Hadley will be specific to your property and situation and we will need to confer with the building department.

See the full text here: Zoning Ordinance

Southampton, MA

Southampton, MA Accessory Dwelling Units (ADU) Rules

City Acceptance Rating: N/A

What you need to know: 

Southampton 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 XI-K Accessory Apartments

Monson, MA

Monson, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: N/A

What you need to know: 

Monson 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

Leverett, MA

Leverett, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: N/A

What you need to know: 

Leverett does not allow detached accessory dwelling units (ADUs). The town allows attached accessory dwelling units under extremely strict circumstances. The town also requires the special permit to be renewed every 2 years. We do not recommend building an ADU of any kind in Leverett.

See the full text here: Zoning Ordinance

Ludlow, MA

Ludlow, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: N/A

What you need to know: 

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

The accessory apartment must be occupied by a family member.

See the full text here: Zoning Ordinance Section 6.6 Accessory Apartments

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

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