The Massachusetts Affordable Homes Act (H. 4977), signed into law on August 6, 2024, includes provisions intended to promote residential housing construction. These provisions: (1) require municipalities to permit accessory dwelling units (“ADUs”) (self-contained housing units, inclusive of sleeping, cooking and sanitary facilities, on the same lot as a principal dwelling) without discretionary zoning relief; (2) extend pre-existing, nonconforming protections to allow construction on previously unbuildable residential lots; and (3) create a toolbox for seasonal communities to use for the promotion of year-round, financially attainable housing.

Accessory Dwelling Units - The bill amends G.L. c. 40A, § 3, the so-called Dover Amendment, to: (1) prevent municipalities from prohibiting or requiring discretionary zoning relief for the creation or rental of ADUs in single-family zoning districts; and (2) prohibit any requirement that the ADU or principal dwelling be owner occupied. Municipalities may still impose reasonable regulations, including site plan review, setbacks, height and bulk limitations and short-term rental bans, and can require one parking space per ADU (but no additional spaces in certain areas in MBTA Communities). The Executive Office of Housing and Livable Communities (“EOHLC”) may issue guidelines and regulations to further clarify this provision.

Residential Lots Under Common Ownership - The bill also amends G.L. c. 40A, § 6 to allow certain vacant lots held in common ownership with adjacent lots to be used for single-family purposes. Previously, municipalities were permitted to treat such commonly owned adjacent lots as a single property for zoning purposes, which effectively prevented construction of an additional single-family house even though the adjacent lot would be buildable if held in separate ownership. The new provision expressly allows construction of a single-family house on the commonly owned lot if the lot: (1) is located within a single-family zoning district; (2) conformed with zoning at the time of its creation; and (3) contains at least 10,000 square feet of area and 75 feet of frontage. If a lot meets these criteria, the new single-family house cannot exceed 1,850 square feet of heated living area, must have at least three bedrooms, and cannot be used as a seasonal home or for short-term rental.

Seasonal Communities - The bill also amends G.L. c. 23B to allow the Secretary of EOHLC to designate “seasonal communities” with the first set of seasonal communities being Nantucket, Martha’s Vineyard, all municipalities on Cape Cod with over 35% seasonal housing units, and all municipalities in Berkshire County with over 40% seasonal housing units. If a municipality accepts the designation, it can take advantage of various new tools intended to promote year-round housing. For example, seasonal communities can acquire year-round housing occupancy restrictions (preventing lots from being used as seasonal homes or for short-term rentals) and can acquire and develop housing for essential public employees (e.g., teachers, public works employees, public safety employees, first responders, town administrators). With some limitations, seasonal communities will be required to adopt bylaws permitting the construction of “tiny homes” (containing 400 square feet of floor area or less, excluding lofts) and allowing construction of attainable year-round housing on undersized lots, provided the housing in each instance is not used as a seasonal home or short-term rental.