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2026 Guide to Landscaping Permits: Suffolk & Nassau County
- Green Horizon Landscaping & Design Writer
- 5 days ago
- 4 min read
Planning a new patio, retaining wall, or landscape project and wondering if you need a permit?
The short answer is: Most likely. While small updates might not require paperwork, significant structural changes on Long Island are strictly regulated. Failing to comply can lead to "stop-work" orders, fines, and major headaches when you eventually try to sell your home.
In 2026, permit laws are enforced at the individual town level. Here is the accurate breakdown for our service areas.
2026 Permit Reference Table
Why Permits are Non-Negotiable in 2026
A permit ensures your project is safe and compliant with local zoning and drainage codes.
Financial Risk: Working without a permit is a gamble that could cost you thousands unplanned landscaping expenses and fines. If a neighbor reports the work, towns can issue a stop-work order and force you to remove the installation at your own expense.
Resale Value: A title search during a home sale will reveal unpermitted structures. This is the #1 reason real estate closings on Long Island get delayed.
Which Projects Typically Need a Permit?
Retaining Walls: This is the most regulated project. In Islip, any wall over 18 inches needs a permit. In Smithtown, the threshold is 30 inches.
Note on Surcharges: Walls supporting surcharge loads (such as driveways, pools, or slopes) typically require engineered plans and may need permits even if they are under standard height thresholds.
Patios & Decks: In Brookhaven, if your patio or deck is more than 8 inches above grade at any point, a building permit is required. Even for grade-level patios, town-specific drainage rules still apply.
Irrigation Backflow: If a backflow device is required for your setup, it is handled under a plumbing permit to ensure it meets your water provider’s (like SCWA) cross-connection standards.
Fences: Rules vary by height and location. In the Town of Oyster Bay, a permit is generally required for any fence over 4 feet in height.
Tree Removal: Rules are often triggered by property size or land-clearing limits. When in doubt, always call your town’s Building or Planning Department before removing mature trees.
Local Rules by Town
1. Town of Islip
Islip is the strictest regarding grade changes. A permit is required for any retaining wall over 18 inches in height. Even for smaller walls, the town requires an Engineering site plan determination to ensure drainage isn't affected.
2. Town of Smithtown
Smithtown requires a building permit for any retaining wall with an exposed height of more than 30 inches. They also have specific zoning cases where permits may be required for smaller installations depending on the location.
3. Town of Brookhaven
For patios and decks in Brookhaven, the key number is 8 inches. If the structure is more than 8 inches above grade, you need a permit. While smaller sheds (up to 144 sq. ft.) may be exempt from certain filings, always verify lot coverage and impervious surface limits for your property.
4. Town of Oyster Bay
Nassau towns like Oyster Bay monitor "Gross Floor Area" and coverage very closely. If you are adding a large patio, we must ensure you aren't exceeding the maximum density allowed for your specific lot.
Green Horizon Handles the Red Tape
Navigating town building departments can be a full-time job. It involves several requirements: to-scale plans, property surveys, and multiple rounds of review.
At Green Horizon Landscaping & Design, managing the permit process is part of our service. We work with the building departments in Brookhaven, Islip, Smithtown, and Oyster Bay to ensure your project is 100% legal and built to last.
Frequently Asked Questions (FAQs)
Do I really need a permit for a small backyard project?
It depends on the scope of the work. While basic gardening usually doesn't require paperwork, any project that changes the structure or drainage of your land like a new retaining wall or a large patio likely does. Permits ensure your project meets local safety and environmental standards.
What happens if I choose to skip the permit process?
Working without a permit is a significant financial risk. If a neighbor reports the work, the town can issue a "stop-work" order and hit you with substantial fines. In some cases, you may even be forced to tear down the entire project at your own expense. Additionally, many Long Island real estate closings are delayed when a title search reveals unpermitted structures.
At what height does a retaining wall require a permit?
Each town has its own threshold. In Islip, any wall over 18 inches requires a permit, and even smaller walls still need an engineering determination. In Smithtown, the limit is 30 inches of exposed height. Other towns like Huntington typically set the threshold at 4 feet.
Will my new patio require a permit in Brookhaven?
In the Town of Brookhaven, patios or decks that are more than 8 inches above grade at any point generally require a building permit. Even for ground-level patios, you must ensure you are following town rules regarding lot coverage and impervious surfaces to avoid drainage issues.
Why do I need a plumbing permit for an irrigation system?
The permit isn't for the sprinklers themselves, but for the backflow prevention device. Both the Suffolk County Water Authority (SCWA) and Nassau providers require these to protect the public drinking water supply from contamination.
Can I just remove a large tree from my front yard?
Not necessarily. Many towns have specific ordinances protecting mature trees. For example, rules are often triggered by the diameter of the tree or the total amount of land clearing on the property. It is always safer to check with your local Building or Planning Department before starting removal.
How much do permit fees usually cost?
Fees vary widely depending on the town and the specific project. While some maintenance permits are relatively affordable, structural permits for walls or major grading can be higher due to the required engineering and safety inspections.