Lexington, Massachusetts’ Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 6/10

Last updated: 2016

What You Need to Know:

The town of Lexington, MA authorizes the provision of Accessory Dwelling Units and is intended to:

Increase the number of small dwelling units available in the Town
Increase the range of choice of housing accommodations
Encourage greater diversity of population with particular attention to young adults and senior citizens; and
Encourage a more economic and energy-efficient use of the Town's housing supply while maintaining the appearance and character of the Town's one-family neighborhoods.

ADU Rules:

An accessory apartment is a second dwelling unit subordinate in size to the principal dwelling unit on a lot, located in either the principal dwelling or an accessory structure.
No more than one accessory apartment on a lot
The owner of the property on which the accessory apartment is to be created must occupy one or the other of the dwelling units, except for temporary absences
The "owner" must be one or more individuals who constitute a family, who hold title directly or indirectly to the dwelling, and for whom the dwelling is the primary residence
Temporary absence of owner. An owner of a property containing an accessory apartment who is to be absent for a period of less than two years may rent the owner's unit as well as the second unit during the temporary absence provided
Written notice thereof must be made to the Building Commissioner on a form prescribed by him
The owner must reside on the property for at least two years prior to and between such temporary absences
The accessory apartment must be designed to maintain the appearance and essential character of a one-family dwelling with accessory structures, subject further to the following conditions and requirements
All stairways to second or third stories must be enclosed within the exterior walls of the dwelling
Where two or more entrances exist on the front facade of a dwelling, one entrance must appear to be the principal entrance and other entrances appear to be secondary.
The apartment must be located in the principal dwelling
The gross floor area of the apartment cannot exceed 1,000 square feet with a maximum of two bedrooms in the apartment.
The gross floor area of the apartment must not exceed 40% of the gross floor area of the principal dwelling, excluding areas of the structure used for parking
The apartment must be located in the principal dwelling
The size of the dwelling must be consistent with typical nearby one-family dwellings.

Notwithstanding the prohibition against having more than one dwelling on a lot, the SPGA may grant a special permit to allow the construction of an accessory apartment in an accessory structure on the same lot as a one-family dwelling if the following criteria are met:

The gross floor area of the apartment does not exceed 1,000 square feet
The SPGA determines that the exterior appearance of the accessory structure is compatible with the principal dwelling on the same lot and with dwellings and accessory structures on adjoining lots.