Massachusetts’ newly passed Affordable Homes Act came into effect in 2025, and it includes language to allow ADUs up to 900 square feet to be built by right in single-family zoning districts throughout the Commonwealth.

ADU, or accessory dwelling unit, tiny homes, or in-law suites, is a small residential unit located on the lot of another property. As of February 2, 2025, ADUs less than 900 square feet can be built by-right in single-family zoning districts statewide, meaning no special permit is required from the local municipality. The principal dwelling and ADU also don’t need to be occupied by the property owner. Financial assistance is also available in some municipality such as Boston.

The amendment of the zoning act presents an opportunity for property owners to increase housing units, boost rental income, and lift their property value.