Bathrooms follow the same logic as kitchens with one difference that matters: there is far more plumbing in a small room, so the odds that your project crosses into permitted work are much higher.
Replacing a vanity, retiling, swapping a toilet for one in the same spot — finish work. Converting a tub to a walk-in shower, moving the toilet, adding a second bathroom, or putting a bathroom in a basement — permitted work, every time.
The line for bathrooms
- Vanity swap, new tile, new mirror, new fixtures in the same locations. Finish work. Generally no permit.
- Tub to walk-in shower conversion. The drain almost always moves and the waterproofing changes. Permit.
- Toilet relocates. Waste line and vent. Permit, and this one is genuinely worth doing properly — a badly vented toilet is a smell you cannot fix later without opening the wall.
- New bathroom where there was none. Permit, and in Suffolk County a new bathroom can also raise a septic question with the Department of Health Services if the house is not on sewer.
- Basement bathroom. Permit, plus egress and ceiling-height considerations, plus the sewage ejector if you are below the main line.
The Suffolk septic question nobody mentions
This is the bathroom-specific trap. If your house is on a septic system rather than sewer — which is most of Suffolk County — adding a bathroom can trigger review by Suffolk County Department of Health Services, because the system was sized for a set number of bedrooms and fixtures.
That review is a separate track from the town building permit and it runs on its own timeline. If you are adding a bathroom rather than redoing one, ask about it before you commit to a schedule. We ran into exactly this on an accessory-apartment project and it reshaped the whole plan — the septic side of Suffolk projects goes into it.
Town by town
The same four departments, the same differences that apply to kitchens. Huntington's ten thousand dollar threshold for sealed drawings catches most full bathroom remodels too. Islip's finish-work exemption covers tile and vanities but not piping. Brookhaven's permit runs one year. Smithtown files online.
The full town-by-town breakdown is here — it is written around kitchens but the departments and the rules are the same ones.
What bathroom work costs here
For context so the permit question sits in proportion: bathroom remodel costs on Long Island covers current numbers. Permit and professional fees are a small share of any of them, and they are almost never the reason a bathroom does not get done.
Verified August 2026. Town requirements and fees change without notice and each department publishes independently. Confirm anything here with your town building department at (631) 312-7441 before you order materials or sign a contract. We are contractors, not your building department, and we would rather you make the call than take our word for it.
Not sure whether your bathroom needs a permit?
Tell us what you want to change and we will tell you straight, before you spend anything.
Suffolk County towns we work in
Bathroom permits are issued by your town, or by your village if you are inside an incorporated one. Suffolk County Department of Health Services is a separate review that applies to septic.
- Brookhaven — Patchogue, Medford, Holbrook, Farmingville, Coram, Selden, Bellport, Shirley, Mastic, Centereach
- Islip — Islip, Bay Shore, West Islip, East Islip, Sayville, Bohemia, Oakdale, Brentwood, Holbrook
- Huntington — Huntington, Northport, Dix Hills, Melville, Greenlawn, Centerport, Huntington Station
- Smithtown — Smithtown, Nesconset, Commack, Kings Park, St James, Hauppauge
- Babylon — Babylon, West Babylon, North Babylon, Lindenhurst, Copiague, Deer Park, Wyandanch
- Riverhead — Riverhead, Wading River, Calverton, Aquebogue, Jamesport
- Brookhaven villages — Port Jefferson, Bellport, Patchogue village and Lake Grove each have their own building department separate from the Town
If your town is not on the list, call anyway — the list is where we work most, not a boundary. Anything from Nassau through the Twin Forks is fair game; we tell you honestly if travel makes a small job uneconomical.
Frequently Asked Questions
Do I need a permit for a bathroom remodel on Long Island?
If you are replacing a vanity, retiling, or swapping fixtures in the same locations, generally no. If the toilet or shower drain moves, if you convert a tub to a walk-in shower, or if you are adding a bathroom, yes.
Do I need a permit to convert a tub to a walk-in shower?
Usually yes. The drain location and the waterproofing both change, which puts the work into permitted plumbing rather than finish work.
Does adding a bathroom require Suffolk County Health Department approval?
It can. If the house is on a septic system rather than sewer, adding a bathroom may trigger review by Suffolk County Department of Health Services because the system was sized for a set number of bedrooms and fixtures. That review runs separately from the town building permit.
Do I need a permit for a basement bathroom?
Yes. A basement bathroom involves new plumbing, usually a sewage ejector pump if you are below the main line, and raises ceiling height and egress questions. It is permitted work in every Suffolk town.
Is retiling a bathroom finish work?
Yes. Tile is finish work and does not require a building permit on its own, the same way paint and carpet do not.
Related Reading
- Kitchen permits by town — the same departments, broken down
- Bathroom remodel cost — what it runs on Long Island
- Bathroom remodeling in Suffolk County — local considerations
- Septic and Suffolk County projects — when the Health Department gets involved
- Walk-in showers — the conversion that usually needs a permit
Ready to Get Started?
Planning a bathroom and not sure what it needs? Call Alec's Construction at (631) 312-7441. Describe it to us and we will tell you straight, before you order anything.