ADU · Westchester County

Can you build an ADU in Mount Vernon, NY?

City of Mount Vernon has 19 districts. All districts prohibit ADUs. Check your address to confirm the district that applies to your parcel:

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What the Mount Vernon code says

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.

Conditions the code attaches:

In R1-7, R1-4.5 and R1-3.6, keeping not more than one roomer in one rooming unit is a permitted accessory use; the rooming unit is within the house, not a separate dwelling unit.
RMF-6.75 permits multifamily buildings of not more than three units, and RMF-10 and RMF-15 allow higher densities.

What the Mount Vernon code indicates by district

The table below shows how each district treats ADUs, alongside the lot and setback standards that govern a second unit. District boundaries and conditions vary, so treat this as a starting point and confirm the district that applies to your parcel.

District	Min lot	Setbacks F / S / R	Max height	ADU
One-Family Residence	0.16 ac	25 / 7 / 20 ft	35 ft	No
One-Family Residence	0.083 ac	20 / 5 / 20 ft	35 ft	No
One-Family Residence	0.1 ac	20 / 5 / 20 ft	35 ft	No
Multiple Family Residenence	0.23 ac	0 / 0 / 30 ft	42 ft	No
Two-Family Residence	0.1 ac	20 / 5 / 20 ft	35 ft	No
Multiple Family Residenence	0.23 ac	20 / 15 / 25 ft	42 ft	No
Three-Family Residence	0.15 ac	20 / 7 / 20 ft	35 ft	No
MVW - Hub (Non-Commercial)	0.23 ac	0 / 0 / 30 ft	42 ft	No
MVW -C (Corridor)	—	0 / 0 / 30 ft	—	No
Apartment House	0.34 ac	20 / 20 / 25 ft	70 ft	No
Commercial Business	0.17 ac	—	30 ft	No
Downtown Business	0.1 ac	—	120 ft	No
Neighborhood Business	0.1 ac	—	30 ft	No
Office Business	0.1 ac	—	45 ft	No
General Industrial	0.11 ac	—	45 ft	No
Landscaped Industrial	0.17 ac	25 / 20 / 25 ft	45 ft	No
Public Institutional	0.11 ac	—	120 ft	No
MVW - Hub	—	0 / 0 / 30 ft	—	No
MVW - Transition	—	0 / 0 / 30 ft	—	No

One-Family Residence, One-Family Residence, One-Family Residence - An accessory structure must be at least 3 ft from the rear lot line.

Multiple Family Residenence, MVW - Hub (Non-Commercial) - The 30 ft setback applies only where a lot line abuts an RMF-10 or RMF-15 district. Along other common lot lines the setback is 0 ft, or 10 ft if a yard is provided (§ 267-19).

Two-Family Residence, Three-Family Residence - Each dwelling unit needs at least 2,250 sq ft of lot area.

An accessory structure must be at least 3 ft from the rear lot line.

Multiple Family Residenence - Each dwelling unit needs at least 1,200 sq ft of lot area.

An accessory structure must be at least 3 ft from the rear lot line.

MVW -C (Corridor) - A building must meet a build-to requirement along 100% of the lot's width on the primary street, rather than sit a fixed distance back (§ 267-19).

The 30 ft setback applies only where a lot line abuts an RMF-10 or RMF-15 district. Along other common lot lines the setback is 0 ft, or 10 ft if a yard is provided.

Apartment House - The side yard is the more restrictive of 20 ft and 1/3 of the height of the highest principal building, so a tall building needs more than 20 ft.

At least 2,250 sq ft of lot area per unit is required for the first two units, and 660 sq ft for each additional unit.

Commercial Business, Neighborhood Business - A parcel contiguous to a residence district must have a rear yard of at least 30 ft and a side yard of at least 20 ft.

Height is also limited to 2 stories.

Downtown Business - A parcel contiguous to a residence district must have a rear yard of at least 30 ft and a side yard of at least 20 ft.

Height is also limited to 10 stories.

Office Business, General Industrial - A parcel contiguous to a residence district must have a rear yard of at least 30 ft and a side yard of at least 20 ft.

Height is also limited to 3 stories.

Landscaped Industrial - Where the lot is adjacent to a residence district, the side yard and the rear yard both rise to 40 ft.

Height is also limited to 3 stories.

MVW - Hub, MVW - Transition - A building must meet a build-to percentage of 70% of the lot's primary-street frontage, rather than sit a fixed distance back from the street (§ 267-19).

The 30 ft setback applies only where a lot line abuts an RMF-10 or RMF-15 district. Along other common lot lines the setback is 0 ft, or 10 ft if a yard is provided.

ADUs vs. short-term rentals in Mount Vernon

Short-term rentals allowed with local rules for City of Mount Vernon. Renting a home short term in Mount Vernon requires a permit from the City, under Article XV of Chapter 267 (Zoning), § 267-97 and § 267-98. These are separate questions from whether you can build an ADU — a unit you're allowed to add isn't automatically one you're allowed to rent nightly, so check both.

Good to know

Residential lot minimum0.083–0.34 ac — an ADU still has to fit the district's lot and setback envelope.
UtilityCon Edison territory.
Zoning codeecode360.com/MO0742
Building dept(914) 665-2483

ADU FAQ — Mount Vernon, NY

Are ADUs allowed in Mount Vernon, NY?

City of Mount Vernon has 19 districts. All districts prohibit ADUs. Check your address with the free ADU checker, or confirm with the building department at (914) 665-2483.

Do I need a special permit for an ADU in Mount Vernon?

No. No district in City of Mount Vernon permits an ADU, so there is no permit to apply for. Codes change, so verify with the building department at (914) 665-2483 before ruling it out.

Can I use an ADU as a short-term rental in Mount Vernon?

Short-term rentals allowed with local rules for City of Mount Vernon. ADU occupancy and short-term-rental rules are separate: an ADU you can build isn't automatically one you can rent nightly. Confirm both before you count on STR income.

Run the free ADU check for your parcel →

What an ADU costs to build in Mount Vernon

Permission is one question and budget is another. An 800 sq ft accessory unit here runs roughly $235k–310k at a standard finish, and the per-square-foot rate comes in above a full house because the kitchen, bath, panel and heating plant cost the same either way. See the full cost to build an ADU in Mount Vernon, priced by size.

How we know this

Sections analyzed: Ch. 267 § 267-17 List of residence district uses (amended 5-12-2021 and by L.L. No. 5-2024); § 267-5 District classification; Art VI Special Permit Uses
Districts confirmed: 19 of 19 — every mapped district.
Last reviewed: 2026-06-15
Not covered here: Overlay districts, the zoning map, and any conditions attached to an individual parcel. Size limits and owner-occupancy terms sit in the code section above, not in this summary.

More on Mount Vernon: Full zoning for new construction · ADU build cost · House build cost · ADU rules across Westchester County · All Westchester County towns

ADU information for City of Mount Vernon is compiled from the municipal code (last reviewed 2026-06-15) and provided for decision-support only — not legal or architectural advice. ADU eligibility, size, owner-occupancy and permit conditions vary by district and often carry exceptions; verify with the building department at (914) 665-2483 before relying on any answer. Source: the Offsite / Aldo zoning dataset.