Building permits in Suffolk County, New York
Find the right authority before you build. Suffolk County permitting follows New York law — here is exactly who issues the permit and where to start.
Cities issue permits
Suffolk County town building departments (10 towns) and incorporated villages (Suffolk County has no county building department)
Suffolk County does not operate a county building department. Residential building permits are issued at the town level — Babylon, Brookhaven, East Hampton, Huntington, Islip, Riverhead, Shelter Island, Smithtown, Southampton and Southold — and by the 33 incorporated villages that run their own building departments. Determine which town or village your property sits in to find the correct permitting authority.
Open the official permit portal →
The county’s role is limited to items such as county roads, drainage, and Department of Health Services approvals for private wells/septic. Confirm the specific town/village building department for the property address.
Permit cheat-sheet (New York rules)
| Project | Permit? | Authority | Typical fee | Timeline | Go / No-Go | Key notes |
|---|---|---|---|---|---|---|
| 🏠 Accessory Dwelling Unit (ADU) | Permit required | city | Permit and plan-review fees set by the city. Verify with the local building department. | Varies by city; NYC ADU filings may take several weeks. | Restricted | New York has no statewide by-right ADU mandate; ADUs are allowed where local law permits (e.g., the NYC ADU program, Buffalo). Zoning applies. Exempt: Allowed only where the local law permits. |
| 🪵 Deck / Porch | Conditional | city | Set by the city — typically a flat plus valuation-based fee. Verify with the city building department. | 1–4 weeks (NYC files through DOB NOW). | Generally allowed | Attached or raised decks need a permit; NYC requires a DOB filing. Exempt: Decks >30 in above grade require a permit (RCNYS R105). |
| 🧱 Fence / Wall | Conditional | city | Usually no building permit under local height limits; zoning setback rules apply. Verify locally. | Same day / Over-the-Counter where required. | Generally allowed | Height/front-yard rules set by local zoning and HOA covenants. Exempt: Typically no building permit under local height limits (zoning). |
| 🛖 Shed / Outbuilding | Conditional | city | No fee under the exemption; a permit fee applies if over the threshold. | Same day / Over-the-Counter where required. | Generally allowed | Larger or serviced sheds need a building permit. Exempt: One-story detached accessory structure ≤120 sq ft is exempt (RCNYS R105.2). |
| 🪜 Basement Finish | Permit required | city | Valuation-based building permit fee. Verify with the city building department. | 2–6 weeks. | Generally allowed | Finishing a basement requires egress (RCNYS R310) and permits; a sleeping room needs a code-compliant egress window. Exempt: N/A |
| 🚗 Garage / Carport | Permit required | city | Valuation-based fee. Verify with the city building department. | 2–8 weeks. | Generally allowed | A new garage requires a building permit under the RCNYS / NYC Building Code. Exempt: N/A |
| ☀️ Rooftop Solar PV | Permit required | city | Electrical permit fee set by the city. Verify with the city building department. | 2–4 weeks (NYC files through DOB NOW). | Generally allowed | Rooftop PV requires an electrical permit; NYC files through DOB NOW. Exempt: N/A |
| 🌡️ HVAC Replacement | Permit required | city | Mechanical permit fee set by the city. Verify with the city building department. | 1–2 weeks. | Generally allowed | Furnace, AC, or heat-pump replacement requires a mechanical permit and inspection. Exempt: N/A |
| 🍳 Kitchen Remodel | Permit required | city | Building + electrical + plumbing permit fees. Verify with the city building department. | NYC: ALT2 review, several weeks. | Restricted | NYC: kitchen/bath renovation needs an ALT2 permit filed by a NYS-licensed PE or RA; upstate follows similar building-permit rules. Exempt: N/A |
| 🛁 Bathroom Remodel | Permit required | city | Building + plumbing + electrical fees. Verify with the city building department. | NYC: ALT2 review, several weeks. | Restricted | NYC: bathroom renovation needs an ALT2 permit filed by a NYS-licensed PE or RA; fixture-only swaps may be exempt. Exempt: N/A |
| 🏗️ Room Addition | Permit required | city | Valuation-based building permit; impact fees may apply. Verify with the city building department. | 3–8 weeks. | Generally allowed | Expanding the footprint requires full plan review; NYC uses New Building / ALT1 filings. Exempt: N/A |
| 🪟 Window / Door Replacement | Conditional | city | Permit fee if changing the opening; in-kind swap is often exempt. | Same day / Over-the-Counter where required. | Generally allowed | Enlarging openings or changes to means of egress need a permit (NYC PE/RA filing). Exempt: In-kind same-size replacement generally needs no permit. |
| 🏘️ Roof Replacement | Conditional | city | Roofing permit fee set by the city. Verify with the city building department. | 1–3 weeks. | Generally allowed | Re-roofing generally requires a permit; NYC requires a roofing permit. Minor repair may be exempt. Exempt: N/A |
| 🅿️ Driveway / Parking Pad | Conditional | city | Private flatwork generally needs no building permit; curb cut / right-of-way needs a separate permit. | Varies. | Generally allowed | A curb cut or work in the public right-of-way requires a separate permit from the city / public works. Exempt: N/A |
| 🏊 Swimming Pool / Spa | Permit required | city | Building permit + electrical; fee set by the city. Verify with the city building department. | 3–8 weeks. | Generally allowed | Pools require a permit and barrier per RCNYS R328 (barrier, alarms, entrapment protection). Exempt: N/A |
| 🧱 Retaining Wall | Conditional | city | No fee under the exemption; a permit applies if over the threshold. | 2–4 weeks if required. | Generally allowed | Taller or surcharge-supporting walls need design and a permit. Exempt: Retaining walls ≤4 ft (bottom of footing to top), not supporting a surcharge, are exempt (RCNYS R105.2). |