Tiny Homes in Cambridge, Massachusetts

Cambridge was an early adopter of flexible accessory apartment rules and remains one of the most ADU-permissive cities in Massachusetts. Under the Cambridge Zoning Ordinance, accessory apartments are allowed inside, attached to, or detached from a primary residence. The principal residence must have at least 1,800 sq ft of gross floor area, and the ADU is capped at 900 sq ft or 35% of the primary residence's gross floor area (whichever is less) — a stricter local cap than the statewide 50% rule. Only one ADU per lot is permitted. The statewide Affordable Homes Act by-right framework also applies where local rules do not override it. A building permit, plumbing permit, electrical permit, and Certificate of Occupancy are required from the Cambridge Inspectional Services Department. Tiny homes of 400 sq ft or less on permanent foundations can use the Appendix AQ pathway from the 10th Edition of 780 CMR. THOWs are regulated as recreational vehicles and cannot serve as primary residences on Cambridge residential lots. Verify current requirements with your local planning department before purchasing land or beginning construction.