Oyster Bay, NY Building Safety: Anti-Mansionization (2026)
Key Facts
- Governing section
- § 246-4.9, gross floor area cap
- Hamlet Overlay, under 6,000 sf
- 40% of lot area max
- Hamlet Overlay, 7,000-9,999 sf
- 2,700 sf plus 20% of excess
- Applies to
- Hamlet Overlay and R1-10/OHG District only
- First offense fine
- Up to $350 or 6 months jail
Summary
The Town of Oyster Bay caps how much floor area a new or expanded house can carry, scaling the limit to lot size instead of imposing a flat number. In the Oyster Bay Hamlet Residence Design District Overlay, a lot under 6,000 square feet tops out at 40% gross floor area, and larger lots get a base square footage plus a shrinking percentage of the excess.
The maximum permitted gross floor area on any residential lot in the Town of Oyster Bay shall not exceed the amounts set forth herein. Oyster Bay Hamlet Residence Design District Overlay. Irrespective of the zoning district in which it is located, the maximum permitted gross floor area on any residential lot in the Oyster Bay Hamlet Residence Design District shall not exceed the amounts as set forth in the following table: Less than 6,000 square feet: 40% of lot area; 6,000 to 6,999 square feet: 2,400 square feet plus 30% of lot area in excess of 6,000 square feet; 7,000 to 9,999 square feet: 2,700 square feet plus 20% of lot area in excess of 7,000 square feet; 10,000 to 19,999 square feet: 3,300 square feet plus 14% of lot area in excess of 10,000 square feet.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4036544; v24 updated 2023-03-07; through 03-07-2023).
Full Breakdown
9 sets a Town-wide ceiling on residential gross floor area, applied district by district through sliding formulas rather than one flat square-footage number. 1 caps a lot under 6,000 square feet at 40% gross floor area; a 6,000-to-6,999-square-foot lot gets 2,400 square feet plus 30% of the area over 6,000 square feet; a 7,000-to-9,999-square-foot lot gets 2,700 square feet plus 20% of the area over 7,000 square feet; and a 10,000-to-19,999-square-foot lot gets 3,300 square feet plus 14% of the area over 10,000 square feet, with the formula continuing to shrink in percentage terms up through lots of five acres or more.
2, starting at 39% of lot area for lots under 7,000 square feet and stepping down through similar break points. 9 in addition to the standard height, coverage and setback limits in the Schedule of Dimensional Regulations. The Department of Planning and Development reviews gross floor area compliance as part of the building permit application under § 93-15.
Violations & Fines
Building beyond the permitted gross floor area is a zoning violation under § 246-14.7.1, punishable by a fine up to $350 for a first offense, $350 to $700 for a second offense within five years, and $700 to $1,000 for a third or later offense within five years, with each week the oversized structure remains counted as a separate violation.
Frequently Asked Questions
Is there a maximum house size limit in Oyster Bay?
How is gross floor area calculated for a lot between 7,000 and 10,000 square feet?
Does the gross floor area cap apply everywhere in Town?
Sources & Official References
Other rules in Oyster Bay
New York rules heatmap·Compare Oyster Bay to another location·View the New York building safety overview
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