Waterways and communities
Islip fronts the Great South Bay from West Islip and Bay Shore east through Islip, East Islip, Great River, Oakdale, Sayville and Bayport, with creeks like the Connetquot River and many residential canals in between. In parts of Islip, the canal and bay bottom in front of private homes is owned by the Town, and that's what makes Islip's rules different.
- West Islip
- Bay Shore
- Brightwaters
- Islip
- East Islip
- Great River
- Oakdale
- West Sayville
- Sayville
- Bayport
Local permits in Islip
Town permit for structures in navigable waters (§ 37-53)
It's unlawful to build any wharf, dock, pier, jetty or other structure in the navigable waters within or bordering the Town without a permit under the Town Code, plus New York State and federal approvals.
Source: Town of Islip Code Ch. 37, Art. III, § 37-53 (ecode360).
Bulkheads on Town-owned bottom (§§ 37-53.1 to 37-53.3)
If your bulkhead or dock touches stream, canal or bay bottom owned by the Town and you have no lease, the Town permits a one-time replacement of existing bulkheading, or a one-time resheathing within 18 inches waterward of the existing wall.
- Encroachments can never occupy more than one-quarter of a canal's or waterway's width.
- New fixed piers and docks on Town bottom can't extend past a water depth of 4 feet below the low-water mark at average tide.
- To prove a structure is "existing," the Town can use prior approvals or aerial evidence from before April 6, 1973, when permits were first required.
- A mitigation fee (per the Planning Department fee schedule) is due before the permit is issued. The land stays the Town's, and your right to encroach can be revoked.
- The Town Assessor can assess marine structures on Town-owned bottom as part of your tax bill.
- Chapter 37, Article III was amended again in September 2026 (L.L. No. 7-2026). Have your contractor check the current text.
Source: Town of Islip Code Ch. 37, Art. III, §§ 37-53.1–37-53.3 (ecode360).
Villages: The Village of Brightwaters handles its own permits. The rest of Islip's Great South Bay shoreline is unincorporated and falls under Town Code Chapter 37.
State layer: most replacements here can use DEC's bulkhead general permit (in place or landward, up to 18 in. higher, no application fee) unless the site is near vegetated tidal wetlands or eelgrass or in an erosion hazard area. Check if you qualify.
What drives the price in Islip
Two Islip-specific costs belong on the quote: the Town mitigation fee for structures on Town bottom, and the possibility of a higher assessment afterward. The 18-inch resheathing allowance can make refacing cheaper than a full replacement when the old wall's anchors are still sound.
Island-wide ranges: bulkhead cost guide & calculator.
Services in Islip
Islip bulkhead & dock FAQ
Who owns the bottom in front of my bulkhead in Islip?
Often the Town. Chapter 37 has specific rules for marine structures on Town-owned stream, canal or bay bottom used without a lease, including a one-time replacement allowance, a mitigation fee and possible tax assessment. Your survey or the Planning Department can confirm it.
Can I put a new wall in front of the old one?
On Town-owned bottom, the Town allows a one-time resheathing within 18 inches waterward of the existing bulkhead. DEC's general permit is tighter (4 inches for timber, 8 inches for corrugated vinyl or steel), so the state limit usually controls.
How far out can a new dock go?
On Town-owned bottom, new fixed docks can't extend past 4 feet of water depth below the low-water mark at average tide, and no encroachment can take up more than a quarter of the waterway's width.