The bill amends sections of the General Laws related to zoning ordinances, specifically focusing on the inclusion of provisions for attached single-family dwellings. It introduces new legal language that mandates zoning ordinances to allow the construction of attached single-family units in designated zoning districts. These units are defined as dwellings constructed side by side or horizontally with a party wall and lot line. The bill stipulates that these units must have access to public water and sewer or approved private systems, and they can be located on their own lots without increased minimum lot size, lot width, lot frontage, or lot depth requirements. Additionally, a zero-lot line setback along the common property line is permitted to accommodate the subdivision of these units, provided that the units comply with building and fire codes.

The bill also specifies that other dimensional requirements of the base zoning district shall apply to the outside perimeter property lines of the end-units of the development, but there shall not be increased dimensional requirements solely applicable to attached single-family structures that are not applicable to other residential structures containing the same density in the same zoning district. Furthermore, cities and towns may establish additional standards for such units, provided that these standards do not restrict a dwelling to less than three stories, limit the 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 states that all towns and cities shall allow attached single-family units in residential districts that permit the construction of two or more units, with the number of attached single-family units allowed being the same as the corresponding residential density for the property and zoning district. The act is set to take effect on January 1, 2026.