Islip, NY Accessory Structures: ADU Rules (2026)
ADU rules in Islip, NY, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Code Section
- Town Code Ch. 68, Art. XLVII (Sec. 68-600 et seq.)
- State law
- NY has no statewide ADU mandate; local ordinance controls
- Owner occupancy
- Required - owner with >=50% interest must live in principal dwelling
- Minimum lot area
- 7,500 sq ft (75 ft minimum width)
- Apartment size
- 300 sq ft minimum; max lesser of 50% or 800 sq ft of principal dwelling GFA
- Max bedrooms
- 2 per accessory apartment
- Location
- Within principal structure only; not in an accessory structure
- Off-street parking
- Minimum 4 spaces
- Permit term
- Renew every 3 years or upon transfer of title
- Approval
- Zoning Board of Appeals permit + public hearing required
Summary
Islip allows an accessory apartment only within the existing structure of an owner-occupied single-family home, on a lot of at least 7,500 square feet, after a Zoning Board of Appeals public hearing and a permit that must be renewed every three years.
No accessory apartment permit shall be granted nor shall any said permit remain valid unless an owner of the lot upon which the accessory apartment is located resides within the principal dwelling unit. ... An accessory apartment shall not be located within an accessory structure.
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
New York has no statewide ADU mandate, so accessory dwelling units in Islip are governed entirely by local law - the Town of Islip Accessory Apartments ordinance (Town Code Chapter 68, Article XLVII, beginning at Sec. 68-600). ' No accessory apartment may be located within an accessory structure such as a detached garage or shed. A permit from the Zoning Board of Appeals plus a certificate of occupancy from the Department of Building are required, and an owner holding at least a 50% interest must reside in the principal dwelling.
The minimum lot area is 7,500 square feet with a minimum lot width of 75 feet; the apartment may have no more than two bedrooms and a gross floor area of at least 300 square feet but no more than the lesser of 50% or 800 square feet of the principal dwelling's gross floor area. There must be no more than one accessory apartment per lot, at least four off-street parking spaces, and the dwelling must be at least seven years old (for homes receiving a C/O after September 1, 1992).
Only one visible front entrance is permitted and no exterior changes that alter the single-family appearance are allowed. The Islip FAQ confirms second kitchens tied to such apartments require special exception approval from the Zoning Board of Appeals after a public hearing and must be renewed every three years (Town Code Secs. 1).
Violations & Fines
All penalties for violations of the accessory apartment article are delineated in Town Code Sec. 68-666. Operating an accessory apartment without a permit, or after expiration, can lead to revocation after a Zoning Board of Appeals hearing; the permit automatically terminates upon death of the applicant, transfer of title, or the owner ceasing to occupy the premises as a principal residence.
Frequently Asked Questions
Can I rent out a detached garage or shed as an apartment in Islip?
Do I have to live in my Islip home to have an accessory apartment?
How big can an Islip accessory apartment be?
Does the accessory apartment permit expire?
Sources & Official References
Other rules in Islip
How Islip compares: Easiest Cities to Build an ADU·New York rules heatmap·Compare Islip to another location·View the New York accessory structures overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.
ADU Rules in Nearby Cities
How other cities in Suffolk County handle adu rules.