If you own a detached or semi-detached one- or two-family home in the Bronx and live on the lot, you may be able to add an ADU. As of October 2026, it can be up to 800 sq ft, and the type depends on your zoning district, flood maps and how much side and rear yard you have.
Where do waterfront rules apply?
Parts of the Bronx along Long Island Sound, Eastchester Bay and the East River include mapped flood risk areas. There, basement, cellar and new backyard ADUs are not allowed. An existing building can still get an above-grade ADU if it meets DOB's elevation requirements, as of October 2026.
Does contextual zoning matter in the Bronx?
It can. Backyard ADUs are not allowed in R1-2A, R2A and R3A districts outside the Greater Transit Zone, and some Bronx neighborhoods of one- and two-family homes are mapped with contextual districts. We confirm your district on the city zoning map.
Which ADU type is common for Bronx homes?
- Attic ADUs in houses with steep roofs.
- Garage conversions where a detached garage sits at the back of the lot.
- Basement ADUs outside flood risk areas, with the egress and sprinkler work they require.
Is there help paying for an ADU?
HPD's Plus One ADU program offers a state grant of up to $175,000 and a city loan of up to $220,000 for eligible owner-occupants, with incomes up to 165 percent of Area Median Income and priority at or below 100 percent, according to HPD's FAQ. A forgivable loan option requires a rent restriction on the ADU.