Islip, NY Zoning Overlays & Bonuses: Density Bonus Law (2026)
Key Facts
- Base density (apartments)
- 9 units/acre
- Base density (attached single-family)
- 6 units/acre
- Absolute cap with bonuses
- 12 units/acre apartments, 10 attached
- Affordable-housing bonus threshold
- 20% of units affordable on site
- Max renewable-energy bonus
- 3 units/acre at 70%+ renewable energy
- Max LEED/NGBS bonus
- 3 units/acre for Gold certification
- Approval authority
- Town Board after public hearing
Summary
The Town Board may grant added density above the base caps of nine units/acre for apartment houses, six for attached single-family homes and four for detached homes in Residence CA-tier districts. Bonuses reward on-site affordable units or renewable-energy/LEED design, follow a public hearing, and can never push density past 12 or 10 units/acre respectively.
A. In accordance with the provisions of Town Law § 261-b, the Town Board is empowered to provide for a system of zoning incentives, or bonuses, as deemed necessary and appropriate to advance the Town's specific physical, cultural and social policies in accordance with the Town's comprehensive plan and in coordination with other community planning mechanisms or land use techniques. B. The Town Board has determined that affordable housing, as well as energy and sustainable design, are suitable community benefits which warrant promotion through the density bonuses hereinafter described... D. At no time shall overall densities exceed 12 units per acre for apartment houses and garden apartments. E. At no time shall overall densities exceed 10 units per acre for attached single-family dwellings.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4826765; v112 updated 2026-02-24; through 02-24-2026).
Full Breakdown
1 gives the Town Board authority, under NY Town Law § 261-b, to award zoning incentives ("density bonuses") to advance affordable housing and energy/sustainable design goals identified in the Town's comprehensive plan. 3 offers a separate, stackable energy/sustainable-design bonus, up to 3 additional units/acre for developments meeting at least 70% of energy needs from renewable sources (measured by Comcheck or an equivalent NYS Energy Code model), and up to 3 more units/acre for LEED Gold or National Green Building Standard Gold certification, with lower tiers (1-2 units/acre) available for lesser renewable-energy percentages or LEED/NGBS Certified or Silver ratings.
Violations & Fines
Bonus density is conditional, not automatic: § 68-173.3A(2) bars construction of the bonus unit(s) until the Commissioner of Planning and Development has verified LEED/NGBS certification, and § 68-173.1C requires Town Board approval through the Department of Planning and Development's Article IVA process before any bonus is used. A project that builds bonus units without completing that approval and certification chain is over its permitted base density and subject to the Town's standard zoning enforcement and building-permit denial.
Frequently Asked Questions
Can any developer in Islip claim a density bonus?
How much extra density can affordable housing earn?
Is there a limit even with multiple bonuses stacked?
What if a project can't meet the affordable or green-design conditions?
Sources & Official References
Other rules in Islip
New York rules heatmap·Compare Islip to another location·View the New York zoning overlays & bonuses overview
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Density Bonus Law in Nearby Cities
How other cities in Suffolk County handle density bonus law.