ADU · Westchester County
Are ADUs allowed in Westchester County, NY?
There is no county-wide answer. In New York an accessory dwelling unit is governed by the town, city or village — so the rule changes at every municipal line, and often between districts inside one town. Below is each of the 43 municipalities in Westchester County, with what its zoning districts actually say.
- 43municipalities with mapped districts
- 29allow an ADU in at least one district
- 0allow one by right somewhere
ADU rules by municipality in Westchester County
Can you build an ADU in Mount Vernon, NY?
All districts prohibit ADUs.
Mount Vernon does not allow an accessory dwelling unit in any district. A second unit on a lot is instead a principal use: § 267-17D permits two-family dwellings as of right in R2-4.5.
Can you build an ADU in New Rochelle, NY?
37 of 38 districts prohibit ADUs. 1 district has incomplete data - verify with the building department at (914) 654-2035.
New Rochelle does not allow an accessory apartment in any of its zoning districts, so the owner of a house lot cannot add a second unit.
Can you build an ADU in Peekskill, NY?
All districts prohibit ADUs.
Accessory dwelling units are not permitted in any Peekskill district. In R - 1A, R - 1B and R - 1C, § 575-22A allows one one-family dwelling per lot, and no building may be arranged or designed for a use the section does not list.
Can you build an ADU in Rye, NY?
13 districts allow ADUs with occupancy restrictions, 10 do not. 2 districts have incomplete data - verify with the building department at (914) 967-7372.
In R-1, R-2, R-3, R-4, R-5, R-6, RA-1, RA-2, RA-3, RA-4, RA-5, RS and RT, a housekeeping unit in an accessory building may house only domestic employees of the owners or tenants of the main building. B-1, B-2, B-3, B-4, B-5, B-6, B-7, C, MC and WR do not permit one.
Can you build an ADU in White Plains, NY?
25 districts prohibit ADUs, 4 allow them with occupancy restrictions. 6 districts have incomplete data - verify with the building department at (914) 422-1269.
Accessory servants quarters are allowed only in R1-30, R1-20, R1-12.5 and R1-7.5, by special permit. Occupancy is tied to domestic employment, so the unit cannot be let to a tenant at large.
Can you build an ADU in Yonkers, NY?
24 of 34 districts prohibit ADUs. 10 districts have incomplete data - verify with the building department at (914) 377-6500.
A new accessory apartment is not allowed in any Yonkers district. § 43-22 only lets certain apartments that existed when the zoning chapter was adopted continue.
Can you build an ADU in Bedford, NY?
9 districts allow ADUs with occupancy restrictions, 6 do not. 3 districts have incomplete data - verify with the building department at (914) 666-8040.
In the 4A, 2A, 1A, 1/2A, 1/4A, TF, VA, EL and DH districts, the Planning Board may grant a special permit for one accessory apartment inside an existing single-family house, and the owner must live in one of the units. The five-year permit must be renewed after re-inspection.
Can you build an ADU in Cortlandt, NY?
12 districts allow ADUs with occupancy restrictions, 4 do not. 5 districts have incomplete data - verify with the building department at (914) 734-1010.
In CROS, R-160, R-80, R-40, R-40A, R-20, R-15, R-10, R-G, CC, HC and HC/9A an attached ADU is permitted and a detached one needs a Planning Board special permit; either way the owner must live in one of the units (§ 307-45C(2)).
Can you build an ADU in Eastchester, NY?
17 of 19 districts prohibit ADUs. 2 districts have incomplete data - verify with the building department at (914) 771-3317.
An accessory dwelling unit is not permitted in R-10, R-15, R-20, R5, R6, R7.5, R1.5, R3, M1, M1500, M350, M700, RTD, DSC, GB, ORB or RB. The Town's route to a second household on one lot is the two-family R3 district, not an accessory unit.
Can you build an ADU in Greenburgh, NY?
19 districts prohibit ADUs, 8 allow them with occupancy restrictions.
The Planning Board may grant a special permit for an accessory dwelling unit in R-5, R-7.5, R-10, R-15, R-20, R-30, R-40 and PUD. The owner must continuously live in one of the units, and the ADU may be rented, but not for less than a one-year term.
Can you build an ADU in Lewisboro, NY?
6 districts allow ADUs with occupancy restrictions, 6 require a special-use permit.
An accessory apartment is a permitted accessory use in every district, but the owner must live in one of the units full time (§ 220-40A(1)) and at most four people may occupy it (§ 220-40A(2)). Some districts also allow a detached second house by Planning Board special permit.
Can you build an ADU in Mamaroneck, NY?
15 districts allow ADUs with occupancy restrictions, 2 do not.
The Town of Mamaroneck has no ordinary accessory apartment. An accessory building on a lot with a main residence may be lived in only by domestic employees of the owners or tenants of the main building who are employed on the premises (§ 240-58B).
Can you build an ADU in Mount Pleasant, NY?
28 districts prohibit ADUs, 3 allow them with occupancy restrictions. 6 districts have incomplete data - verify with the building department at (914) 742-2305.
An accessory apartment is allowed only on one-family residential properties in R-40, R-20 and R-10, by a Planning Board permit issued only to the owner-occupant of the principal dwelling (§ 218-36).
Can you build an ADU in New Castle, NY?
9 districts prohibit ADUs, 8 allow them with occupancy restrictions.
One accessory apartment is allowed per one-family lot in the one-family residence districts, with site development plan approval rather than a special permit, if an owner of the lot lives in one of the units as a principal residence (§ 60-420B(5)).
Can you build an ADU in North Castle, NY?
22 districts prohibit ADUs, 8 allow them with occupancy restrictions. 1 district has incomplete data - verify with the building department at (914) 273-3000.
An accessory apartment needs a Planning Board special permit and is allowed only in R-4A, R-2A, R-1.5A, R-1A, R-3/4A, R-1/2A, R-10 and R-5. The owner of the lot must live in one of the units for as long as the permit lasts (§ 355-40K).
Can you build an ADU in North Salem, NY?
11 of 12 districts allow ADUs with occupancy restrictions. 1 district has incomplete data - verify with the building department at (914) 669-5952.
An apartment accessory to a single-family detached house needs a Board of Appeals special permit in R-1, R-2, R-4, R-1/2, R-1/4, NB, GB, PO and RO, and the owner must live in one of the units (§ 250-68). That approval belongs to the owner, not the property.
Can you build an ADU in Ossining, NY?
9 districts allow ADUs with occupancy restrictions, 4 do not. 4 districts have incomplete data - verify with the building department at (914) 762-8419.
An accessory apartment on a single-family lot needs a Zoning Board of Appeals special permit, and the owner must live in the house or the apartment as a primary residence (§ 200-31.2). It is available in R-40, R-30, R-20, R-20A, R-15, R-10, R-7.5, R-5 and MF.
Can you build an ADU in Pound Ridge, NY?
5 districts prohibit ADUs, 2 allow them with occupancy restrictions.
Accessory apartments may be located only in R-2A and R-3A, in the main house or in a conforming accessory building, and the owner of the lot must live in one of the two units. Every new accessory apartment needs Planning Board site plan review.
Can you build an ADU in Somers, NY?
8 districts prohibit ADUs, 5 allow them with occupancy restrictions. 2 districts have incomplete data - verify with the building department at (914) 277-3539.
In the residence districts, an accessory apartment on a one-family building lot needs a Zoning Board of Appeals special exception use permit, and the owner must live in one of the units. It may go only in a building constructed or issued a building permit before April 1, 1992.
Can you build an ADU in Yorktown, NY?
17 districts prohibit ADUs, 7 allow them with occupancy restrictions. 2 districts have incomplete data - verify with the building department at (914) 962-5722.
In R1-200, R1-160, R1-80, R1-40, R1-20, R1-10 and R-2, an existing single-family house can be converted to include an accessory dwelling unit by Zoning Board of Appeals special permit after a public hearing. One dwelling unit must be owner-occupied (§ 300-38B(8)).
Can you build an ADU in Harrison, NY?
All districts prohibit ADUs.
Harrison does not allow an accessory dwelling unit or accessory apartment in any zoning district, and all unlisted uses are prohibited in all districts.
Can you build an ADU in Ardsley, NY?
7 districts prohibit ADUs, 3 allow them with occupancy restrictions.
An accessory dwelling unit is allowed only in the R-1, R-2 and R-3 districts, one per lot with a one-family dwelling, and the owner must live in the house or the unit (§ 200-100.20). The Village caps the total at 50, so confirm the cap has not been reached.
Can you build an ADU in Briarcliff Manor, NY?
18 districts prohibit ADUs, 4 allow them with occupancy restrictions.
An accessory dwelling unit is allowed only in an accessory building that existed on July 1, 2014, and only in the R80A, R60A, R40A and R40B districts. The deadlines to create a new unit have passed, so this is a legalization route for existing units, not a way to build a new one.
Can you build an ADU in Bronxville, NY?
All districts prohibit ADUs.
An accessory apartment is not allowed in any Bronxville district. Residence AAA allows a one-family dwelling, not more than one on each lot (§ 310-8A(1)), and Residence AA and Residence A allow the same uses as Residence AAA.
Can you build an ADU in Buchanan, NY?
8 districts allow ADUs with occupancy restrictions, 2 do not.
The Planning Board may grant a special permit for an accessory apartment in a single-family detached house in the R-7.5, R-10, R-15, R-20, R-40, C-1 and C-2 districts (§ 211-22B(1)). The owner must live in the house or the apartment as a primary residence.
Can you build an ADU in Croton-on-Hudson, NY?
9 districts prohibit ADUs, 8 allow them with occupancy restrictions. 2 districts have incomplete data - verify with the building department at (914) 271-4783.
In RA-60, RA-40, RA-25, RA-9, RA-5, RB, RC and O-1, an accessory apartment in a single-family detached house, or an accessory cottage, is permitted with Planning Board approval on a lot with no more than one dwelling unit (§ 230-41A). The owner must live in one of the units.
Can you build an ADU in Dobbs Ferry, NY?
12 districts prohibit ADUs, 9 allow them with occupancy restrictions. 1 district has incomplete data - verify with the building department at (914) 231-8513.
In OF1, OF2, OF3, OF4, OF5, OF6, MDR1, MDR2 and MDRH, the Planning Board may grant a special permit for an accessory dwelling unit, and the owner must live in the house or the ADU as a principal residence (§ 300-39B(3)). The Village caps ADU special permits at 50.
Can you build an ADU in Elmsford, NY?
9 of 10 districts prohibit ADUs. 1 district has incomplete data - verify with the building department at (914) 592-6555.
An accessory dwelling unit is not permitted in R-0, R-1, R-2, R-3, RCD, B, CB, LO or LI. In R-2 and R-3 a single-family house can instead become a two-family with a Village Board of Trustees special permit, a change of use; the permit expires after five years or on a sale.
Can you build an ADU in Hastings-on-Hudson, NY?
9 districts prohibit ADUs, 9 allow them with occupancy restrictions. 8 districts have incomplete data - verify with the building department at (914) 478-3400.
One accessory dwelling unit is allowed on a lot whose principal use is a single-family house in the R-20, R-10, R-7.5, 2R, 2R-3.5, MR-2.5, MR-1.5, MR-O and MR-C districts, if the owner occupies one of the units as a principal residence (§ 295-53.2B).
Can you build an ADU in Irvington, NY?
9 districts allow ADUs with occupancy restrictions, 2 do not. 2 districts have incomplete data - verify with the building department at (914) 591-8335.
An accessory apartment needs a Planning Board special permit, and the owner must occupy the principal dwelling or the apartment as a principal residence. A family-only in-law apartment inside a single-family house needs only a registration with the Village Clerk.
Can you build an ADU in Larchmont, NY?
All districts prohibit ADUs.
An accessory apartment is not a permitted use in any Larchmont district: R-30, R-20, R-15, R-12.5, R-10, R-7.5, R-5, MF, W, RB or RC. A use absent from a district's enumerated lists is not available there (§ 381-3A).
Can you build an ADU in Mamaroneck, NY?
21 districts prohibit ADUs, 1 requires a special-use permit. 1 district has incomplete data - verify with the building department at (914) 777-7731.
An accessory dwelling unit is not allowed in any Village of Mamaroneck district except C-1, where the Planning Board may grant a special permit for a residence as a use accessory to a permitted principal use on the Boston Post Road (§ 342-50A(2)).
Can you build an ADU in Mount Kisco, NY?
24 of 25 districts prohibit ADUs. 1 district has incomplete data - verify with the building department at (914) 864-0019.
An accessory dwelling unit is not allowed in any Mount Kisco district except CL-1, where the rule is not confirmed. In the residential districts, customary accessory uses may not include any activity conducted as a separate residence (§ 110-8B(3)(g) for RS-12).
Can you build an ADU in Ossining, NY?
All districts prohibit ADUs.
An accessory apartment or other accessory dwelling unit is not permitted in any district of the Village of Ossining. A second household comes only as a principal use, such as a two-family dwelling, and only in some districts.
Can you build an ADU in Pelham, NY?
All districts prohibit ADUs.
Accessory dwelling units are not permitted in any Village of Pelham district. Each district's use section bars any use other than the ones it lists.
Can you build an ADU in Pelham Manor, NY?
6 districts prohibit ADUs, 5 allow them with occupancy restrictions. 1 district has incomplete data - verify with the building department at (914) 738-8820.
In R-AAA, R-AA, R-A, R-B and MF, a second living unit on a single-family lot is allowed only for live-in staff: a chauffeur, servant, nurse or other health-care provider employed full-time on the premises, and their relatives by blood, marriage or adoption (§ 210-31C).
Can you build an ADU in Pleasantville, NY?
13 districts prohibit ADUs, 4 allow them with occupancy restrictions.
An accessory apartment is allowed by special permit on a one-family lot in RRR, RR, R and R-1, including a lot nonconforming as to bulk requirements, and the owner must live in one of the units as a principal residence (§§ 185-31A, 185-32A, 185-32B).
Can you build an ADU in Port Chester, NY?
12 districts prohibit ADUs, 4 allow them with occupancy restrictions.
An accessory dwelling unit is allowed only in CD-3, CD-3.R20, CD-3.R7 and CD-3.R5, on a lot whose principal use is a single-family dwelling, with a special exception permit. The permit voids on sale or vacancy unless a complete submission for a new permit is made within 60 days.
Can you build an ADU in Rye Brook, NY?
10 districts allow ADUs with occupancy restrictions, 7 do not. 2 districts have incomplete data - verify with the building department at (914) 939-0668.
In R-25, R-20, R-15, R-15A, R-12, R-10, R-7, R-5, R2-F and RA-1, a building behind the main building may house only domestic employees of its owners or tenants. OB-1, OB-2, OB-3, OB-S, C1, C1-P and H-1 appear not to permit one, and the rule in P.U.D. is not confirmed.
Can you build an ADU in Scarsdale, NY?
All districts prohibit ADUs.
Accessory dwelling units are not permitted in any Scarsdale district. Each use list is closed, and no building may be used, or built or altered to be used, for a purpose it does not include; the one-family list allows one detached dwelling for one family per lot (§ 310-7A).
Can you build an ADU in Sleepy Hollow, NY?
14 districts prohibit ADUs, 1 allows them with occupancy restrictions. 2 districts have incomplete data - verify with the building department at (914) 366-5116.
R-1 allows quarters for full-time domestic employees as an accessory use, a second living unit that cannot be let to a tenant at large. An accessory unit is not permitted in R-2, R-2A, R-3, R-4A, R-4, R-5, R-6, C-1, C-2, CEM, H, PP, RF or P.
Can you build an ADU in Tarrytown, NY?
15 districts prohibit ADUs, 9 allow them with occupancy restrictions.
In R-80, R-60, R-40, R-30, R-20, R-15, R-10, R-7.5 and R-5, a single-family dwelling may add an ADU with a Building Department permit, and the owner must live in the main house or the ADU as a primary residence. The ADU may not be rented for less than six months at a time.
Can you build an ADU in Tuckahoe, NY?
8 of 9 districts prohibit ADUs. 1 district has incomplete data - verify with the building department at (914) 961-8148.
An accessory apartment is not allowed in any Tuckahoe district, and each district prohibits any use it does not list. RES A-10 allows a one-family dwelling, not more than one on each lot (§ 4-1.1), and RES A-5 allows the same uses (§ 4-2.1.1).
ADU questions people ask about Westchester County
Are ADUs allowed in Westchester County?
There is no single county-wide answer — ADUs are governed by each town, city and village, not by the county. Of the 43 Westchester County municipalities with mapped zoning districts, 29 allow an accessory dwelling unit in at least one district, and 0 allow one by right somewhere. The section for your municipality below gives the specific answer.
Does Westchester County issue ADU permits?
No. Zoning approval and building permits both come from the municipality — the town, city or village — not the county. County health departments do commonly review septic and water supply for a new dwelling unit, which is often the binding constraint on a rural lot.
What size ADU can I build in Westchester County?
Size caps are set per municipality and frequently per district, and they are one of the details most often stated wrongly by national ADU sites. Open your municipality's page below for the code sections analyzed, then confirm the current figure with the building department before you design to it.
What an ADU costs to build in Westchester County
Permission and budget are separate questions. See the Westchester County cost-to-build breakdown for current per-square-foot ranges — an accessory unit runs above a full house per square foot, because the kitchen, bath, panel and heating plant cost the same at any size.
More on Westchester County: Zoning for new construction by town · Cost to build · ADU rules across every county we cover
ADU information for Westchester County is compiled from each municipality's own code , most recently reviewed 2026-09-29, and provided for decision-support only — not legal or architectural advice. Eligibility, size, owner-occupancy and permit conditions vary by district and often carry exceptions; confirm with the municipality before relying on any answer. 24 of the 43 municipalities below still have one or more districts that have not been analyzed, and each says so in its own section. Source: the Offsite / Aldo zoning dataset.