Boston’s Mattapan zoning amendment creates attached and detached ADU paths only for parcels within both the Greater Mattapan Neighborhood Zoning District and PLAN: Mattapan study area. The City fact sheet describes owner-resident ADUs.
Local standards
The selected local standards are summarized in the Mattapan Residential Code Zoning Changes Fact Sheet. A detached unit’s floor plate is limited to the lesser of 900 square feet or the primary structure’s floor plate. It may be no taller than 1.5 stories or the primary structure, whichever is lower, and must be at least five feet from another structure on the lot. For an attached addition, added GFA is the lesser of 75% of primary-unit GFA or 1,250 square feet, and the addition cannot exceed the primary structure’s height.
Confirm the applicable rule
The fact sheet also summarizes coverage, permeable-area, yard, and subdistrict unit-count rules. Floor plate, GFA, and total building coverage are separate measurements. Confirm both geographic boundaries, subdistrict, owner-residence condition, lot-size row, and current Article 60/Article 2 text. Zoning measurements do not by themselves establish fire separation, building-code compliance, utility capacity, or permit approval. For shared measurement methods, see the setback and separation guide and floor-area guide.
