This bill amends the existing zoning ordinances in the General Laws to include provisions for the construction of attached single-family dwellings in designated zoning districts. It introduces new legal language that defines "attached single-family dwelling" as a dwelling unit constructed side by side or horizontally and separated by a party wall and lot line. The bill outlines specific conditions under which these units may be constructed, including the requirement for access to public water and sewer or approved private systems. It allows for each single-family unit to be located on its own lot without increased minimum lot size, lot width, lot frontage, or lot depth requirements, and permits a zero-lot line setback along the common property line.

Additionally, the bill states that other dimensional requirements of the base zoning district shall apply to the outside perimeter property lines of the end-units, but there shall not be increased dimensional requirements solely applicable to attached single-family structures. Cities and towns may establish additional standards for these units, provided that such standards do not restrict a dwelling unit's floor area ratio to less than one, limit the number of bedrooms to less than three, or require more than one off-street parking space for up to two bedrooms, and two off-street parking spaces for up to three bedrooms.

The bill also revises existing sections of the zoning ordinances to ensure that zoning regulations address the permitting of attached single-family units in residential districts that allow for the construction of two or more units, with the number of units allowed corresponding to the residential density for the property and zoning district. The act is set to take effect on January 1, 2026, allowing municipalities time to adjust their zoning ordinances to comply with the new requirements.