In Suffolk County your building permit comes from your town or, if you live inside an incorporated village, from your village. But Suffolk differs from Nassau in one way that catches homeowners out: the Suffolk County Department of Health Services may also have to approve your project — and on a property with a septic system, that approval can decide whether the job is possible at all.
That second approval is the part nobody warns you about. A dormer that adds a bedroom, or a bathroom addition that moves a waste line, can require county sign-off on top of your town permit. Homeowners find out late, and late is expensive.
Who Issues What
| Approval | Who grants it |
|---|---|
| Building permit | Your town, or your village if you are inside one |
| Sanitary / septic approval | Suffolk County Department of Health Services, Office of Wastewater Management |
| Plumbing and electrical certificates | Town-approved inspection agencies, filed alongside the permit |
The two tracks run in parallel. The town will not close out your job without the county piece where the county piece is required.
The Suffolk Difference: When the County Has to Approve Your Renovation
Much of Suffolk County is unsewered. Where a property is on a septic system, Article 6 of the Suffolk County Sanitary Code governs, and it is written in terms most homeowners never encounter until they are already mid-project.
“No Developer or Property Owner shall … engage in the creation of a New or Expanded Single-Family Residence … unless prior Department approval has been obtained for the existing or proposed water supply and Sewage disposal facilities.”
— Suffolk County Sanitary Code, §760-604(A)(3)
Everything turns on what counts as an “Expanded Single-Family Residence.” The Code defines it at §760-603, and the definition is broader than people expect. It includes:
- Building a new single-family residence
- Any addition or modification to an existing residence that requires adding or modifying sewage disposal facilities
- An accessory structure that requires adding or modifying sewage disposal facilities
- Adding one or more bedrooms beyond the number previously approved by the Department’s Office of Wastewater Management
Read that last one twice. It is not about square footage or cost. If your project adds a bedroom and pushes you past the bedroom count the county has on file for your septic system, you need county approval — even though the bedroom itself has nothing to do with plumbing.
That is precisely what a dormer or an attic conversion does. It is the single most common way a straightforward Suffolk renovation turns into a sanitary review.
Touching the septic system itself
“After July 1, 2019 … no Property Owner, contractor, or Developer shall engage in an OWTS Replacement or an OWTS Retrofit of an existing Cesspool or Individual Sewerage System for any permanent structure unless Department approval is obtained.”
— Suffolk County Sanitary Code, §760-605(B)(1)
“Retrofit” is defined broadly. Replacing or adding a septic tank, adding leaching structures, or re-configuring system piping all count. Parcels inside an approved proposed sewer district are excluded.
| Office of Wastewater Management | Division of Environmental Quality 360 Yaphank Avenue, Suite 2B, Yaphank, NY 11980 |
|---|---|
| Phone | 631-852-5800 |
If your home is on public sewer, none of this applies to you. Confirm which you are on before assuming either way — sewer coverage in western Suffolk is patchy and varies street by street.
The Three Western Suffolk Town Building Departments
If you are not inside an incorporated village, this is where your permit comes from.
| Town | Building Department | Contact |
|---|---|---|
| Babylon | 200 East Sunrise Highway Lindenhurst, NY 11757 Mon–Fri, 9:00 a.m.–4:30 p.m. |
631-957-3058 Online filing only since 2 February 2026 |
| Islip | Building Division One Manitton Court, Islip, NY 11751 Mon–Fri, 8:00 a.m.–4:00 p.m. |
Permits 631-224-5466 BuildingPermits@islipny.gov |
| Huntington | Building & Housing, Town Hall 100 Main Street, Room 115 Huntington, NY 11743 |
631-351-3000 Online Permit Portal |
Town-by-town notes worth knowing before you file
- Babylon moved to OpenGov. Since 2 February 2026 all applications and supporting materials must be submitted online through the Town’s Online Permit Center. Paper intake was paused for the switchover. The Building Department sits within Planning & Development, and the town is blunt about the rule: “No building can be constructed or altered on any lot, plot, or premises until a Town of Babylon building permit authorizing the work has been issued.”
- Islip runs separate desks for permits, plan examiners, inspections, zoning and plumbing, each with its own direct line. Knowing which desk you need saves days. The town also prefers email over phone.
- Huntington splits filings three ways — Commercial Building, New Residential Dwelling, and Alteration or Structure. Filing under the wrong one sends the application back. Building & Housing is part of the Engineering Services Department.
If You Live in an Incorporated Village
As in Nassau, villages run their own building departments with their own codes, inspectors and review boards. The town has no jurisdiction over your permit.
The incorporated villages in these three towns are:
- Town of Babylon — Amityville, Babylon, Lindenhurst
- Town of Islip — Brightwaters, Islandia, and the Fire Island villages of Ocean Beach and Saltaire
- Town of Huntington — Asharoken, Huntington Bay, Lloyd Harbor, Northport
Village requirements can be stricter than the town’s and stricter than people expect. Lloyd Harbor, for example, publishes a permit reference chart that extends to tree removal and vista cutting — and warns that failing to get the right approval can mean delays, stop-work orders, fines and added cost.
Village boundaries do not reliably match mailing addresses. Confirm which authority you are under before anything is filed.
What Happens If You Skip It
- Stop-work orders and fines, mid-build
- No certificate of occupancy for the completed work
- Trouble at resale, when a municipal search turns up open or absent permits
- On septic properties, a much worse problem — unapproved sanitary work can mean tearing out and redoing a system that is already in the ground
How We Handle Suffolk Permits
We are a licensed general contractor and have been building on Long Island since 1976. Permits are part of the job, not an extra you chase separately.
- We identify the correct authority — town or village — before anything is filed
- We establish early whether your property is on sewer or septic, because that single fact changes the approval path
- We flag county sanitary review when a project adds a bedroom or moves waste lines, rather than discovering it mid-build
- We schedule inspections and carry the project through to certificate of occupancy
Suffolk County Permit Questions
Does Suffolk County issue building permits?
No. Your building permit comes from your town or, if you live inside an incorporated village, from your village. Suffolk County’s role is separate: the Department of Health Services approves water supply and sewage disposal facilities under Article 6 of the Suffolk County Sanitary Code, which matters on properties with septic systems.
Do I need a permit to remodel a kitchen in Suffolk County?
In almost all cases, yes. Towns and villages require permits for interior alterations, and work involving plumbing, electrical, gas or structure requires a permit and inspections. Purely cosmetic work such as painting or replacing cabinet doors generally does not.
Does Suffolk County have to approve my renovation if I am on septic?
It depends on what the project does. Under §760-604 of the Suffolk County Sanitary Code, prior Department approval is required for a New or Expanded Single-Family Residence. That includes any addition or modification requiring the addition or modification of sewage disposal facilities, and the addition of one or more bedrooms beyond the number previously approved by the Office of Wastewater Management.
Does adding a dormer require Suffolk County approval?
If the dormer adds a bedroom and takes you past the bedroom count the county has on file for your septic system, then county approval is required in addition to your town or village building permit. If it adds no bedroom and does not change sewage disposal facilities, generally it does not. Confirm with the Office of Wastewater Management at 631-852-5800.
Do I need county approval to replace my septic system?
Yes. Since 1 July 2019, no property owner or contractor may carry out an OWTS Replacement or OWTS Retrofit of an existing cesspool or individual sewerage system without Department approval. Retrofit is defined broadly and includes replacing or adding a septic tank, adding leaching structures, or re-configuring system piping.
How do I file a building permit in the Town of Babylon?
Online only. Since 2 February 2026 all Town of Babylon applications and supporting materials must be submitted through the Town’s Online Permit Center.
Planning a Renovation in Western Suffolk?
We handle the permit process as part of the project — the right authority, and the county sanitary question answered before it becomes a problem. Free consultation and a written line-item estimate.
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Building permits in all 64 Nassau villages ·
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