Islip's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Islip, New York, there are 5 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.

Tiny Homes

Islip has no tiny-home ordinance; a standalone tiny house on wheels or a separate small cottage is not a permitted use, and the only path to a small second dwelling is an accessory apartment within an owner-occupied principal home meeting the New York State Uniform Code.

Key details: Code Section: Town Code Ch. 68, Art. XLVII; Sec. 68-45; NYS Uniform Code. Standalone tiny home: Not a permitted use - detached dwellings not allowed as accessory. Only small-dwelling path: Accessory apartment inside owner-occupied principal home. Accessory structure height: 14 ft max (most residential zones). Plumbed accessory building: Counts toward FAR regardless of size.

Placing or occupying a standalone tiny home or unpermitted detached dwelling is a zoning violation subject to Town of Islip code enforcement and penalties under Chapter 68. An unpermitted habitable accessory structure must be removed, brought into compliance, or legalized through the Zoning Board of Appeals, and it can never qualify as an accessory apartment because the ordinance bars apartments in accessory structures.

Compared to other cities, Islip takes a harder line on tiny homes. The enforcement and penalty structure reflects that.

Garage Conversions

Islip permits private garages whose gross floor area does not exceed the main dwelling's ground-floor living area, but converting a garage to living space or adding a second kitchen requires Building Division permits and, for an accessory apartment, Zoning Board of Appeals special-exception approval.

Key details: Code Section: Town Code Sec. 68-48 (garages); Secs. 68-600, 68-419.1 (second kitchen). Max garage GFA: Cannot exceed main dwelling's ground-floor living area. Garage door height: 8 ft maximum (residential). Detached garage: Must meet accessory-structure setbacks and height. Second kitchen: Only with permitted accessory apartment or two-family use; ZBA special exception.

Converting a garage to a dwelling or adding a second kitchen without the required permits and special-exception approval is a zoning violation enforceable by the Building Division. Illegal apartments are subject to revocation, code enforcement, and penalties; an accessory apartment created in an accessory structure can never be legalized because the ordinance prohibits that location.

Carport Rules

Carports and other accessory structures in Islip follow the same accessory-building rules: no placement in the primary front yard, size-based side and rear setbacks of 2 to 10 feet, a 14-to-18-foot height cap, and no more than 25% rear-yard occupancy.

Key details: Code Section: Town Code Sec. 68-45; General Zoning Standards Chart. Front yard: Accessory structures prohibited in primary front yard (except Fire Island). Behind front of dwelling: 4 ft if <=6 ft high; 20 ft if >6 ft high. Side/rear setback: 2 ft (<=144 sq ft) / 4 ft (144-500) / 10 ft (>=500). Max height: 14 ft (most residential zones); 18 ft in GST, CA, RRD.

A carport or other accessory structure placed in a primary front yard, exceeding the height cap, or violating setback and rear-yard occupancy limits must be removed or relocated, or the owner must obtain a variance from the Zoning Board of Appeals. Construction without a required permit subjects the owner to Town of Islip code enforcement.

Shed Rules

A shed in Islip may be built without a permit if it is 144 square feet or less, no more than 8 feet high, has no electric or plumbing, is the only shed on the lot, and meets setbacks; larger or taller sheds require a building permit.

Key details: Code Section: Town Code Sec. 68-45; Sec. 68-23(C)(2); General Zoning Standards Chart. No-permit shed limit: <=144 sq ft, <=8 ft high, no electric/plumbing, only shed on lot. Side/rear setback (<=144 sq ft): 2 ft. Side/rear setback (144-500 sq ft): 4 ft. Side/rear setback (>=500 sq ft): 10 ft.

A shed that exceeds the no-permit thresholds, lacks setbacks, or pushes rear-yard occupancy past the limit (so less than 40% of the rear yard remains landscaped earth) must be removed or legalized through a Zoning Board of Appeals variance application. Building without a required permit subjects the owner to Town of Islip code enforcement and penalties under Chapter 68.

ADU Rules

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.

Key details: 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.

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.

Compared to other cities, Islip takes a harder line on adu rules. The enforcement and penalty structure reflects that.

The Bottom Line

Islip is tougher than many cities when it comes to accessory structures. Out of the 5 rules covered here, 2 are rated strict. If you are a homeowner, renter, or business owner in Islip, take the time to understand these requirements before they become a problem. Most violations come with fines, and some repeat violations can escalate.

Keep in mind that Islip can amend these rules at any council meeting. For the most current version of any rule mentioned here, check the specific ordinance page, where we track updates as they happen.