Bathroom Remodeling in Brentwood, NY

Brentwood is Town of Islip. Where a house holds more than one household, a second bathroom question is frequently really a question about whether the second unit is legal, which is a different track entirely.

What we see in Brentwood bathrooms

Where a Brentwood house holds more than one household, a second bathroom question is frequently really a question about whether the second unit is legal. That is a different track entirely from a bathroom remodel, and it is worth being straight about before money is spent rather than after a filing raises it.

For an ordinary bathroom in the main house, the usual Islip logic applies: tile and fixtures in place are finish work, anything that moves water is filed.

What needs a permit in Brentwood

Vanity swap, retiling, new fixtures in the same places — finish work, generally no permit. Toilet or shower drain moves, tub converts to a walk-in shower, a bathroom gets added, or a bathroom goes in a basement — permitted work, every time.

The Suffolk catch: adding a bathroom to a house on septic rather than sewer can trigger a Suffolk County Health Services review, because the system was sized for a set number of fixtures. It runs separately from the town permit, on its own timeline. Redoing an existing bathroom does not raise it. Filing detail for Town of Islip Division of Building.

Four things decide whether a bathroom lasts, and none of them are the tile: the subfloor, the venting on a moved toilet, the waterproofing membrane behind the tile, and where the exhaust fan actually terminates. What to ask about each. We measure on site for free and put the number in writing as a scope with a total.

Verified August 2026. Requirements and fees change and each department publishes independently. Confirm anything here with the Town of Islip Division of Building at (631) 224-5466 before you order materials or sign a contract.

Also serving, near Brentwood

We are based in East Patchogue and work across Suffolk County. If you are inside an incorporated village, the village building department governs rather than the town.

• Patchogue
• Medford
• Islip
• Bay Shore
• Smithtown

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

Does adding a bathroom to a basement apartment need a permit?
Yes, and it usually raises a larger question first: whether the apartment itself is legal under the Town of Islip's accessory apartment rules. A bathroom filing on an unpermitted unit tends to surface that. It is far better to know where you stand before spending, and legalizing is a real path rather than a dead end.

Do I need a permit for a bathroom remodel in Brentwood?
Replacing a vanity, retiling or swapping fixtures in the same locations is generally finish work and needs no building permit. Moving the toilet or shower drain, converting a tub to a walk-in shower, or adding a bathroom is permitted work. There is far more plumbing in a bathroom than a kitchen, so that line gets crossed more often.

Does adding a bathroom in Suffolk County need 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 is separate from the town building permit. Redoing an existing bathroom does not raise it.

Is tile waterproof?
No. Tile is not waterproof; the membrane behind it is. Ask specifically what waterproofing goes in behind the tile, because it is the part you never see and the only part that decides whether the wall lasts.

Related Reading

• Bathroom permits by town — the full breakdown
• Bathroom remodel cost — 2026 Long Island numbers
• Walk-in showers — the conversion that needs a permit
• Septic and Suffolk projects — when SCDHS gets involved
• Bathroom remodeling in Suffolk — local considerations