Stamford, CT Accessory Structures: ADU Owner Occupancy (2026)

Stamford's Zoning Regulations define an Accessory Dwelling Unit (ADU) as a dwelling unit on the same lot as a larger Principal Dwelling Unit, either attached, built within, or detached from it, with both units required to stay under common ownership. Before the Zoning Enforcement Officer will issue an ADU permit, the property owner must reside on the premises, and at the time of the Building Permit application the owner has to submit a sworn affidavit attesting to that residency. The rule, adopted under application 222-28 and effective October 11, 2022, runs alongside a set of companion conditions: attached ADUs must meet every standard of the underlying zoning district, detached ADUs must meet either the Accessory Building standards or the Single-Family Dwelling standards for that district, the lot may hold no more than one single-family dwelling and must be at least 10,000 square feet, and occupancy of the ADU itself is capped at three people.

Multi-family lots, including nonconforming two- and three-family dwellings, cannot add an ADU at all. Because the requirement is a permit condition rather than a stand-alone violation, the city's leverage is the permit itself: if the affidavit turns out to be false, or the owner later stops occupying the premises, the ADU is out of compliance with Section 4 and can be treated as an illegal use. The regulations are current through the May 31, 2026 amendment cycle and cross-reference Section 12's parking standards, which require one added off-street space for every ADU.