Where this starts
A buyer walks a 1,000 square foot ranch on a 60 by 125 lot and says the words every agent here has heard: we will just put a second floor on it. Or a seller lists a house with a dormer that went up twenty years ago and finds out at contract that the village has no permit on file for it. Both of them are dealing with the same three numbers, and neither has looked them up yet.
Why it comes up on the houses I sell here
All eight of the houses I have closed in Lindenhurst were under 1,200 square feet. The median was 1,071 square feet, on a median lot of 7,500 square feet, and the median year built was 1955, the oldest 1946 and the newest 1972. A house that size on that lot uses about 14 percent of the ground, which is why the first question a buyer asks is not whether they can add on, but how much, and in which direction.
That is a zoning question before it is a construction question, and in Lindenhurst the answer depends on which side of the village line the house sits.
Which code applies: village or town
Lindenhurst is an incorporated village inside the Town of Babylon, with its own zoning ordinance, Chapter 193 of the village code, and its own building department at Village Hall, 430 South Wellwood Avenue. North Lindenhurst is not in the village. It is unincorporated and falls under the Town of Babylon's zoning, Chapter 213, and the town's building department. A Lindenhurst mailing address does not tell you which one you are dealing with. The survey and the tax map number do.
The rest of this guide is about the village, because that is where my Lindenhurst sales have been. Where the town differs, I say so.
The village numbers
The village publishes its zoning board agendas, and those agendas state each limit in the village's own words as it applies it. Across the September 2024 and March 2025 hearings the residential limits cited were:
- Lot occupancy: 20 percent of the lot.
- Height: 26 feet.
- Side yards: 10 feet minimum on each side, 25 feet in aggregate.
- Front yard: 25 feet. Rear yard: 25 feet.
- Accessory structures: two, each at least 5 feet from side and rear lines, up to 14 feet high and 600 square feet.
- Driveway width: 22 feet. Front yard greenery: 70 percent minimum.
The side yard rule is written into the B Residence article of the code:
In case of a single-family dwelling, there shall be two side yards, one on each side of the main building, the aggregate width of which shall be at least 25 feet. Neither side yard shall be less than 10 feet.
Village of Lindenhurst Code, Chapter 193, Article V, B Residence Districts
Height is measured from the crown of the road in front of the house to its highest point, chimneys excepted, under the definitions article of the same chapter. That is why the permit application asks for elevation data from the centerline of the road on any second story or dormer job: the village is checking the 26 feet from the street, not from your foundation.
What those numbers do to a 1,071 square foot house on 7,500 square feet
Twenty percent of 7,500 square feet is 1,500 square feet of footprint. A one story house of 1,071 square feet already uses 1,071 of that. The remaining 429 square feet has to cover everything else the village counts as occupancy, and the agendas show it counts a lot: a front portico, a rear deck, an in-ground pool, a shed. On the September 2024 agenda one homeowner needed a variance to keep a front portico that took lot occupancy from 20 percent to 22.06 percent. On the March 2025 agenda a 14 by 28 foot pool took another house to 28.51 percent.
So a ground floor extension on a typical lot here runs into the 20 percent line quickly, and a second floor is the obvious answer, because it adds floor area without adding footprint. It works, provided two things are true.
First, the existing walls have to sit at least 10 feet from each side line, because a second floor built on the existing footprint inherits its setbacks. A March 2025 application asked to reduce the minimum side yard from the required 10 feet to 8.9 feet in connection with construction of a second floor addition. The house was 8.9 feet from the line already. The second floor could not go up over it without the board's permission.
Second, the finished house has to stay under 26 feet from the crown of the road. On a lot that sits below street grade that is a real constraint. A September 2024 application for a second floor addition and front portico asked for 31 feet, plus a front yard of 20.44 feet against the required 25 and lot occupancy of 25.31 percent. Three variances for one project is not unusual on these agendas.
The variance, and what the board has to weigh
Anything outside those limits goes to the village Zoning Board of Appeals. The application has to be notarized and filed with a full disclosure affidavit and a copy of the survey showing every structure on the property. The board meets the fourth Wednesday of every month at 7:00 p.m. at Village Hall, and the applicant appears in person, by agent or by attorney.
The board is not free to decide on a whim. New York's Village Law fixes the test for an area variance, and the village agendas cite it on every notice:
the benefit to the applicant if the variance is granted, as weighed against the detriment to the health, safety and welfare of the neighborhood or community by such grant
New York Village Law section 7-712-b(3)
The five factors the board considers are whether the change would alter the character of the neighborhood or hurt nearby properties, whether the applicant could get the same benefit some other feasible way, whether the variance is substantial, whether it would affect physical or environmental conditions, and whether the difficulty was self-created. Self-created does not by itself defeat an application, but it counts against it, and buying a house that is 8.9 feet from the line and then asking to build up over it is a self-created difficulty in the board's terms. The board must grant the minimum variance it deems necessary.
What the permit actually requires
For a second floor or dormer the village building department's own requirements sheet asks for:
- A survey dated within five years, with dimensions and locations of every existing and proposed structure, and height elevation data from the centerline of the road for any second story or dormer. For a dormer or second floor where lot occupancy is not in question, a survey up to ten years old is accepted, provided no other permits have been issued since.
- Plans sealed and signed by an architect. The sheet is explicit that all dormer construction and all first and second story additions require architect-sealed plans. Raising the dwelling requires a structural engineer's report as well.
- Eight photographs of the whole property, and proof of workers' compensation and disability insurance or a waiver.
- A $25 non-refundable filing fee, and a permit fee based on the estimated cost of construction: $100 for the first $1,000 and $15 for each additional $1,000. On a $150,000 second floor, by that formula, the permit is $2,335. The fee is doubled for legalizing work that already exists.
- A plumbing permit before the building permit is released if the work adds bath fixtures or heating, and an electrical certificate before any certificate of occupancy is issued.
Applications filed from 31 December 2025 must comply with the 2025 edition of the New York State Uniform Building and Fire Prevention Codes. The building department is at (631) 957-7510, Monday to Friday, 8:00 a.m. to 3:30 p.m., and inspections are by appointment on Mondays, Tuesdays, Thursdays and Fridays.
One more line on that sheet matters to buyers here more than sellers expect. If the alterations would add a second kitchen, even for personal use, a two family use application has to be granted before the building permit is issued. A "mother/daughter" setup is not a construction detail in this village. It is a use the board has to approve first.
The flood rule that sits underneath all of it
Lindenhurst is on the south shore, and much of it is in a mapped flood zone. I wrote about what that does to a sale in my guide to Lindenhurst flood zones, which sits beside this one. The part that reaches into this guide is the 50 percent rule: when the value of an improvement exceeds half the market value of the structure, the whole building has to be brought to current floodplain standards, which in a mapped zone can mean lifting the house. A second floor on a 1955 slab ranch can cross that line. The permit sheet already contemplates it, which is why raising a dwelling has its own engineering requirement, and why a September 2024 application combined raising the existing dwelling with a first floor addition and a new front entry. Before pricing a second floor, get the structure's market value and the flood zone in front of you, because together they decide whether the job is an addition or a rebuild.
Outside the village: North Lindenhurst
In the Town of Babylon's C Residence district, which covers much of the unincorporated area north of the village, the town code allows 30 feet or two and a half stories, requires side yards totalling 25 feet with neither under 10 feet, and a front yard of 30 feet. The town's Building Department, not the village, issues the permit and the town's Zoning Board of Appeals hears the variance. The lot area and building coverage limits for that district are in sections 213-94 and 213-100 of the town code, and the figures depend on the district the specific parcel carries, so confirm them for the address rather than assuming the village numbers carry across.
What to do, in order
- Pull the survey and confirm whether the address is inside the village or in the Town of Babylon. If the survey is older than five years, or older than ten for a dormer or second floor, budget for a new one.
- Measure the existing side yards on the survey. Anything under 10 feet on either side, or under 25 feet combined, means a second floor over that wall needs a variance.
- Work out lot occupancy now: house footprint plus porch, deck, shed and pool, divided by lot area. If it is already near 20 percent, a ground floor extension is a variance application, not a permit application.
- Ask the village building department what is on file for the address. An unpermitted dormer or finished basement comes out at contract, and legalizing it costs double the permit fee.
- Check the FEMA flood zone and get a rough market value on the structure before pricing the job, so the 50 percent rule is a number and not a surprise.
- If a variance is needed, file the notarized application, affidavit and survey and get on the fourth Wednesday calendar early. Projects on these agendas commonly carry two or three variances at once, and the board weighs each.