ADU rules in White Plains

White Plains has no accessory dwelling unit and no accessory apartment use anywhere in its zoning ordinance, and Section 5 closes the door explicitly: any use not specifically listed as permitted is deemed prohibited. Section 4.4.1 separately allows no more than one main building plus its accessory buildings on a lot outside multi-family districts and conservation developments, so a second detached house on a one-family lot is not possible. The single accessory living-quarters use in the whole ordinance is 'Accessory servants quarters', a special permit use in only the four largest-lot one-family districts (R1-30, R1-20, R1-12.5, R1-7.5); it is nowhere defined, has no size or occupancy standard, and has no individual standards in Section 6.7, so it is a narrow discretionary path for household staff quarters rather than a rentable backyard ADU. The 178-item amendment list in Appendix A, running from 1981 through December 1, 2025, contains no ADU or accessory apartment amendment.

There is no accessory or internal ADU, but a second unit inside the building is possible where 'Two family dwelling' is a Permitted Principal Use: R2-4, R2-2.5, RM-2.5, RM-1.5, RM-1.5T, RM-1, RM-0.7 and RM-0.35. All five one-family districts (R1-30, R1-20, R1-12.5, R1-7.5 and R1-5) permit only a one-family dwelling, so a basement or internal conversion there is prohibited outright. Where two-family is allowed the conversion is gated by minimum lot area per dwelling unit (4,000 sq ft per unit in R2-4, 2,500 in R2-2.5 and RM-2.5, 1,500 in RM-1.5 and RM-1.5T, 1,000 in RM-1, 700 in RM-0.7, 350 in RM-0.35) and by 2 off-street parking spaces per unit. Note the legal form: a two family dwelling is defined as a dwelling containing two principal dwelling units, so neither unit is accessory to the other and neither is subject to ADU-style size or occupancy limits.

Because the ordinance contains no ADU, there is no square-foot or percent-of-primary-dwelling cap to quote. A two-family conversion is bounded by the residential dimensional schedule instead: R2-4 permits 0.55 FAR and 25 percent total building coverage for a two-family on a minimum 5,000 sq ft lot with 4,000 sq ft of lot area per dwelling unit; R2-2.5 permits 0.65 FAR with 2,500 sq ft per dwelling unit; main-building height is capped at 2 1/2 stories and 30 ft (35 ft in R1-30 and R1-20). Detached accessory buildings, the form an accessory servants quarters would take, are capped by accessory building coverage of 5 percent of the lot in R1-30 and R1-20, 7 percent in R1-12.5 and R1-7.5 and 10 percent in R1-5 and the R2 districts, plus a 15 ft accessory-structure height limit and setbacks of 5 to 15 ft from side and rear lot lines. Footnote (u) further caps R1 lots over 40,000 sq ft at 8,000 sq ft of total building coverage, 5,000 sq ft of main building coverage and 0.30 FAR.

The zoning ordinance imposes no owner-occupancy condition on any residential use. There is no ADU permit to attach one to, and the two-family dwelling use in the R2 and RM districts carries no residency requirement, nor does the accessory servants quarters special permit (Section 6.7 sets no individual standards for it). New York has no statewide ADU statute that would impose or preempt such a rule; General City Law Section 20 leaves zoning to the city. Owner occupancy matters in one practical way only: Municipal Code Section 4-29-3 exempts owner-occupied single-family dwellings, and two-family dwellings where one unit is owner-occupied, from the annual Rental Housing Registry and License Program, so living on site avoids the license, but it is never a condition of building or occupying a unit.

Section 8.3's schedule requires 2 off-street spaces for a one-family dwelling and 2 spaces per dwelling unit for a two-family dwelling, so converting a house into a legal two-family means providing four off-street spaces on the lot. An accessory servants quarters special permit use requires 1 space, and keeping roomers requires 1 space per roomer. There is no transit-proximity reduction, no small-unit exemption and no fee-in-lieu for these residential uses. The requirement has teeth at the end of the process: Section 8.1 bars issuance of a certificate of use and occupancy until the required spaces have actually been established.

The review depends entirely on which path a homeowner takes. A two-family dwelling in R2-4, R2-2.5 or an RM district is a Permitted Principal Use, and Section 7.1.1 exempts one-family and two-family dwellings (on parcels with no environmentally sensitive feature) from site plan approval, so the conversion is ministerial: a building permit and certificate of use and occupancy from the Department of Building. An accessory servants quarters in R1-30, R1-20, R1-12.5 or R1-7.5 needs a special permit, and because the use appears in neither the Common Council list (Section 6.2.1) nor the Planning Board list (Section 6.2.2) the approving agency defaults to the Board of Appeals, which must hold a noticed public hearing within 45 days and apply the general standards of Section 6.5. In every other case, including any second unit in R1-5 or a detached second dwelling, the use is prohibited and would require a use variance from the Board of Appeals under Section 10.3.5.1.

Nothing in the zoning ordinance bars renting a legally created dwelling unit on a long-term basis. Doing so triggers Municipal Code Chapter 4-29, the Rental Housing Registry and License Program in effect since July 3, 2018, which makes it unlawful to operate a rental housing unit without a Rental Housing License from the Department of Building, valid January 1 through December 31 and tied to periodic self-inspections; Section 4-29-3 exempts owner-occupied single-family dwellings, two-family dwellings where one unit is owner-occupied, condominiums and co-ops, buildings over twelve units, and hotels and rooming houses. White Plains has no short-term rental, vacation rental or bed-and-breakfast ordinance at all: a 'Hotel' is defined as rooms without individual kitchen facilities occupied by transient guests and is not a listed use in any residence district, and Section 5 prohibits any use not specifically listed, so nightly rental in a residential zone has no zoning basis. Landlords also fall under Municipal Code Chapter 9-8, adopted as Local Law 2-2025 on June 10, 2025, which opts the city into New York's Good Cause Eviction law (Real Property Law Article 6-A) and defines a small landlord, exempt from it, as one owning no more than four units anywhere in the state.