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Greenburgh, NY Accessory Structures: ADU Rules (2026)

Significant Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

ADU rules in Greenburgh, NY, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Governing section: Code § 285-36(O)
Adopted: April 8, 2026 (Local Law 2-2026)
ADUs per lot: One maximum
Minimum lot size: 7,500 to 20,000 sq. ft.
Approval required: Planning Board special permit
Penalty: $1,000 minimum fine, permit revocation

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in New York under recent ADU streamlining laws. The Greenburgh, NY rules below cover local size, height, and setback requirements.

Summary

Greenburgh allows one accessory dwelling unit per lot only in the R-5 through R-40 and PUD districts, and only after the Planning Board grants a special permit under Code § 285-36(O). Minimum lot sizes, unit-size caps and district conformance all apply before an ADU can be built.

O. Accessory Dwelling Units. ADUs shall be permitted upon issuance of a special permit by the Planning Board and only in the following districts: R-5, R-7.5, R-10, R-15, R-20, R-30, R-40, and PUD. ADUs shall additionally be permitted upon the issuance of a special permit by the Planning Board in connection with new subdivision and site plan applications filed after the effective date of this local law approval. (1)(a) There shall be no more than one ADU per buildable lot, which may be located within the principal one-family residence or in a detached structure. An ADU shall not be permitted on a buildable lot that contains an existing two-family residence or greater, unless approved in connection with a Planned Unit Development.

View official code

Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4570580; v39 updated 2025-10-22; through 10-22-2025).

Full Breakdown

Local Law No. 2-2026, adopted by the Town Board on April 8, 2026, added subsection O to Code § 285-36 to create a townwide ADU framework. 5, R-10, R-15, R-20, R-30, R-40 and PUD zoning districts, plus new subdivision or site-plan applications filed after the law's effective date. Only one ADU is allowed per buildable lot, and it can sit inside the principal one-family home or in a detached structure, but a lot already containing a two-family or larger residence cannot add one unless it is part of a Planned Unit Development.

Minimum lot size scales with the type of ADU: 20,000 square feet for a new detached structure added to the principal home, 10,000 square feet where the ADU expands an existing dwelling, and 7,500 square feet where the ADU sits inside the existing footprint or converts a lawful existing accessory structure with no expansion; no ADU is permitted on a lot under 7,500 square feet. The property and its structures must still meet the underlying district's lot area, yard and other zoning requirements, and ADUs are limited to lots served by public water and public sanitary sewer.

A complete application must be filed with the Department of Community Development and Conservation within one year of the section's adoption unless extended by local law, and approved applicants must start construction within six months of permit issuance and finish within one year.

Violations & Fines

Violating any ADU provision or a Planning Board condition triggers revocation of the ADU special permit and a fine of not less than $1,000 under § 285-36(O)(19). Sworn compliance affidavits are due annually by January 10 to the Building Inspector, and a permit lapses automatically if construction does not begin within 12 months of approval without a Planning Board extension.

Frequently Asked Questions

Can any homeowner in Greenburgh add an ADU?

Only in the R-5, R-7.5, R-10, R-15, R-20, R-30, R-40 and PUD districts, and only after obtaining a special permit from the Planning Board under Code § 285-36(O). Lots under 7,500 square feet cannot host an ADU at all.

How many ADUs can one lot have in Greenburgh?

No more than one ADU per buildable lot, whether it is built inside the main house or in a detached structure. Lots that already contain a two-family or larger residence cannot add an ADU unless approved as part of a Planned Unit Development.

What happens if I violate Greenburgh's ADU rules?

The Town can revoke the ADU special permit and impose a fine of not less than $1,000 under § 285-36(O)(19). Owners also must file sworn compliance affidavits annually by January 10 with the Building Inspector.

Sources & Official References

[1]Town of Greenburgh Local Law No. 2-2026 (amending Code Ch. 285)

Other rules in Greenburgh

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All Greenburgh rules

How Greenburgh compares: Easiest Cities to Build an ADU·New York rules heatmap·Compare Greenburgh to another location·View the New York accessory structures overview

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