Attached ADU, Convert Existing Space, Detached ADU Chris Lee Attached ADU, Convert Existing Space, Detached ADU Chris Lee

Swampscott, MA

Swampscott, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 8/10 (10 is most accepting)

Last updated: 7.2.2024

Image Source: North of Boston

What You Need To Know

Last winter, at Swampscott’s annual town meeting, a law was passed to make ADUs by right.  There are a number of restrictions and design requirements based upon what type of ADU you want to build.  

Type of ADU Permit Required

ADUs are permitted by right in Swampscott.

ADU Rules

Size Restrictions

  • Generally, ADUs are permitted to be as large as 50% of the floor area of the existing dwelling or 900 feet, whichever is smaller

Attached ADUs

  • If changing the footprint of an existing structure the floor area addition is limited to 800 square feet.

    • An addition of greater than 800 square feet is subject to site plan review by the Swampscott planning board

Detached ADUs can be built in two ways

  • ADUs can be built in existing detached accessory structures.  

    • If in a preexisting, nonconforming location, it can be demolished and rebuilt within the same footprint.  These cases are subject to a finding from the Zoning Board of Appeals.

    • If building a new construction detached ADU, the ADU must meet the dimensional requirements for a detached structure.

      • 5 feet from side and rear setbacks and no less than 10 feet from the primary structure. 

Additional Rules

  • Only one ADU is permitted per lot.

  • If an ADU is constructed where the entrance is located on the front of the home, only one entrance may appear to be the primary entrance.

  • Any exterior stairways to the ADU must be located on the side or rear of the dwelling.

  • All utilities must be shared between the ADU and the primary dwelling.

  • The owner of the lot must either live in either the primary dwelling or the ADU, except for a bona fide temporary absence.

  • In addition to minimum parking requirements, one additional parking space is required for the ADU.  

Resources:

Town of Swampscott Zoning By-law- Article 5.11.0.0/Page 119

https://www.swampscottma.gov/sites/g/files/vyhlif1296/f/pages/swampscott_zoning_by-laws_version_5_15_23_0.pdf

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Arlington, MA

Arlington, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 8/10

Last updated: 6.2.2024

Image source: Visit Lexington

What You Need To Know

Arlington, 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 Arlington 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 Arlington

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Montague, MA

Montague has very favorable rules related to backyard homes (ADUs). There are limited restrictions and their zoning bylaw overall does not place excessive regulations on what can be built on a someone’s land. Setback requirements are also some of the most accommodating in Western Mass. However, homeowners still need to apply for a special permit to build a detached ADU so it will be important to plan a project that considers neighbors and the public if your ADU will be visible from the street.


Montague, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 8/10 (10 is most accepting)


Evaluate your property:

Download D.I.Y. Guide

What you need to know:

Montague has very favorable rules related to backyard homes (ADUs). There are limited restrictions and their zoning bylaw overall does not place excessive regulations on what can be built on a someone’s land. Setback requirements are also some of the most accommodating in Western Mass. However, homeowners still need to apply for a special permit to build a detached ADU so it will be important to plan a project that considers neighbors and the public if your ADU will be visible from the street.

Type of Permit Required:

Living Space Conversion:

Conversion of space within an existing home can be done with only a building permit.

Additions and Detached:

Both new additions, conversion of existing detached structures and newly constructed detached structures require a Special Permit.

ADU Rules in Montague:

  • Only one Accessory Apartment may be created on a single-family lot.

  • Utilities, water & sewer must be integrated with the single-family dwelling.

  • The owner must occupy either the ADU of primary home.

  • The ADU must maintain the single-family character of the home

  • The ADU’s design must match the character of the home

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

  • New stairways to provide access or egress to the ADU shall be enclosed, screened, or located so they are not visible to the public.

  • A ADU cannot be larger that 900 SF

  • A minimum of two (2) off street parking space must be provided and the entire lot can not have more than 4.

  • Minimum lot size requirements are waved in districts AF-1, RS-2 and RB

  • The Building Inspector or the Zoning Board of Appeals may allow reasonable deviation from the stated conditions to accommodate features that facilitate access and mobility for disabled persons



See Dimensional Requirements (extracted12/14/2019)

See the full Zoning Ordinance here: Zoning Ordinance Section 8.5.2 Accessory Apartments

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Amherst, MA

In 2014, Amherst joined many cities in MA by revising bylaws making it easier for homeowners to install accessory apartments in all zoning districts. They have very straight forward rules in their zoning ordinance, but design requirements are strict and certain neighborhoods are harder to obtain approvals than others due to fears about student tenants and noise.

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=

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