Home Inspection on Long Island, NY

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A home inspection on Long Island starts with the county line. The Census Bureau’s 2020–2024 survey puts the median year built at 1955 in Nassau and 1970 in Suffolk. About 47% of Nassau’s homes went up in the 1940s and 1950s, against 22% of Suffolk’s, and 44% of Suffolk’s homes burn fuel oil against 26% of Nassau’s. Under both counties sits one groundwater system, which the U.S. Geological Survey calls the sole source of drinking water for nearly 3 million people, and that shared water explains much of what a Long Island buyer is asked to think about: wells, cesspools, tanks, basements and flood insurance.

Inspecwise is based in South Ozone Park, Queens. We are a New York State–licensed home inspector, certified by InterNACHI, and we work in both Long Island counties as well as the five boroughs and Westchester. This page is our Island-wide guide for buyers. It sets out what the census, FEMA’s flood-claims file and federal and state water sources say about both counties, where they differ, and what each difference means on inspection day. For county detail, read our Nassau County guide and our Suffolk County guide; for two places in depth, see Levittown and Hicksville and Huntington. If you are comparing the Island with the city, our New York City overview is the place to start, and every county and neighborhood page is listed under areas we serve.

Nassau and Suffolk side by side: two counties built in two eras

Figures: Census Bureau, American Community Survey, 2020–2024 five-year estimates. Each carries a margin of error, so a gap of a point or two means nothing. The gaps that matter here are large: Nassau’s median house is 15 years older than Suffolk’s, and the share of Suffolk homes that burn oil is about 18 points higher.

Nassau got its housing in one generation, and the record is public. The State Comptroller’s 2007 report on the county says William Levitt began building more than 17,000 standardized, partially prefabricated homes on former potato farms in 1947, that other communities developed in Levittown’s wake, and that the county’s population surged in the 1950s and 1960s, peaking at 1.4 million in 1970 after a 251 percent rise since 1940 (NYS Comptroller, Report 10-2007). The census shows the result: 76% of Nassau’s homes are detached houses, and 79% date from before 1970. Garden City is the older model. The National Park Service records that in 1869 A. T. Stewart bought a 500-acre parcel there to create a model planned city (National Park Service suburbs study), and the census shows the older start: 35% of the homes in ZIP 11530 date from 1939 or earlier, against 19% for the county.

A house from the 1950s has had time to need more than one roof, boiler and electrical service. The Standards of Practice have us describe the heating fuel and equipment, the service amperage and voltage, any aluminum branch wiring, the piping materials and the water heater’s capacity and energy source (19 NYCRR 197-5.8, 5.9 and 5.10), and report what looks deficient, but not how long any of it will last or what it will cost to fix (197-5.16). A buyer of a 1950s house should therefore ask the seller for dates: when the boiler, the roof and the service were replaced, and by whom.

Suffolk is a younger county, with 69% of its homes built in 1960 or later, but it is not uniformly young. The table below covers the Suffolk ZIP codes we pulled. Babylon (ZIP 11702) has 25% of its homes from 1939 or earlier and Islip (ZIP 11751) 19%, while Hauppauge (ZIP 11788) has 1% from that era and 89% built in 1960 or later. A ZIP code marks where the mail goes, so its edges do not follow village, hamlet or school-district lines.

Figures: the same census survey at ZIP level, with place names from the Postal Service’s mail-delivery list and not from municipal boundaries. The Huntington-area ZIP codes are on our Huntington page.

One aquifer system under two counties: what the sole-source designation does and does not mean

EPA’s sole-source aquifer program starts with a simple test: the aquifer must supply at least half of the drinking water for its service area (EPA’s program overview). EPA’s national list shows Nassau and Suffolk together as one designated aquifer. USGS describes it as the sole source of drinking water for nearly 3 million people, drawn from three principal aquifers, the upper glacial, the Magothy and the Lloyd, by about 50 water suppliers across the two counties (USGS Fact Sheet 2021-3044). EPA’s own pages give two different years for the designation, so we leave the year out.

What the designation does is narrow. The program as EPA describes it reviews proposed projects that are both inside the review area and federally funded. What it does not do is rate the water in any house. The USGS sampled Long Island wells and found at least a few PFAS chemicals, or 1,4-dioxane, or both, in every sampled well, and in some wells above New York’s limits for drinking water; those are groundwater samples and not tap water. What reaches a faucet depends on the supplier, the treatment and the house’s own pipes, so the designation is a reason to read your supplier’s annual report and to test the tap if you have a question, not a reason to expect a problem. A home inspection does not answer the question: under the Standards we are not required to report on water potability, water conditioning, wells or a private water supply (197-5.8). Our water quality testing page explains the lab route, and our well water guide covers houses with a private well.

Groundwater and basements: the water table is not high everywhere

Buyers on Long Island hear that the water table is high and that every basement is therefore damp. The USGS reports say something narrower, and the difference changes what a buyer should ask. The agency’s regional maps place the water table in the upper glacial aquifer throughout the island, except in parts of central and eastern Nassau and western Suffolk where it sits in the shallow Magothy (USGS Scientific Investigations Map 3326). That says which layer holds the water table. It does not say how deep the water table is below your lawn, and depth is what decides whether a basement is wet.

Depth varies, and USGS maps the variation. Its depth-to-water maps mark shallow areas in red as places where potential substructure flooding may occur, and the map’s stated vertical error is plus or minus 5 feet. Its October 2026 report (USGS Scientific Investigations Report 2026-5042) finds the south shore flatter and the water table closer to the land surface than on the north shore, names basement flooding as the concern where the water table is shallow in suburban residential areas, and notes that a shallow water table raises the chance of groundwater interacting with sewer, septic and water-distribution systems. It cites typical residential basement depths of about 6 to 10 feet and typical New York septic tanks at 6 to 7 feet. The same report separates a damp basement from a flooded yard: groundwater emergence, meaning the water table rising above the land surface, is highest on the coast and near surface water, and USGS’s summary of the report says inland areas away from surface waterbodies are not likely to be exposed to it.

The report states the limits of its maps plainly. The 2026 map works in 900-meter grid cells, about 3,000 feet, so local features are not well represented and the result is not a house-level answer, and it models average conditions, so it may underestimate the hazard near the coast. Its 6-foot sea-level scenario is a modeled case and not a forecast. The table below sets out the practical reading.

A home inspection on Long Island is not a hydrogeology study. The Standards ask us to look at the grade and water drainage next to the foundation, to report visible signs of water penetration and to operate any sump or ejector pump within reach. They do not require moisture meters or other special instruments, and they do not ask us to evaluate geological or soil conditions (197-5.6, 197-5.16). A buyer who wants to know how a particular basement behaves in a wet month has to get that from the seller’s answers, the neighbors, the pump’s history and, where the house is near the water, the flood map. See also our basement inspection page.

South Shore and North Shore: slope, soil, sewers and storm surge

Long Island’s two ridges, the Harbor Hill and Ronkonkoma moraines, merge in the west and separate in central Nassau, and the land slopes gently toward the south and more abruptly toward the north, according to USGS (USGS groundwater atlas). Outwash sand and gravel cover much of the rest of the island, and the bedrock does not crop out anywhere on it. The 2026 report adds that the unconsolidated deposits are more than 2,000 feet thick beneath the south-central part and that sandy soils are the most common hydrologic soil group in both counties. None of this is a rule about a particular lot.

For a buyer the contrast is about what to ask. On the south side, ask about water in the basement and crawlspace, the flood zone and insurance history, and whether the sewer line has been scoped. On the north side, ask about the slope and how water is carried away from the house, about retaining walls and steps, and about what kind of sewage system serves the house, because the Standards have us observe retaining walls, walkways and steps (197-5.4) but not a septic system.

Cesspool, septic tank or sewer: the question every Long Island buyer has to answer

Long Island’s wastewater is the second water question after drinking water, and the two are linked. DEC’s Long Island Nitrogen Action Plan fact sheet says nitrogen comes mainly from wastewater, including residential cesspools, plus fertilizer and stormwater runoff, and that discharge from cesspools and septic systems reaches groundwater and then the bays (DEC fact sheet). Its Nassau plan describes Long Island cesspools as vertical cylinders with no leach field, and says onsite systems in Nassau generally consist of cesspools, or septic tanks connected to leaching rings, that drain to groundwater and do not remove nitrogen.

The state’s disclosure form asks every seller of a one- to four-family house what the sewage system is, with four options: public sewer, private sewer, septic or cesspool. For a septic system or cesspool it also asks its age, the date it was last pumped and how often it is pumped (Real Property Law §462). Our own report states whether the water supply and waste disposal are public, private or unknown (197-5.8). Beyond that the Standards stop: septic systems, cesspools and underground drainage fall outside what we must observe. If the house is sewered, a camera inspection of the line to the connection is a separate service; our sewer scope guide explains it. If it is not, a pumping and inspection by a specialist is the way to learn the condition.

Two Nassau programs are worth knowing about. DEC’s 2025 summary says Nassau’s SEPTIC program funds eligible residents, small businesses and non-profits to replace conventional cesspools or septic systems with what DEC calls I/A systems, with 195 installations to date, and that the Bay Park Conveyance Project will carry treated wastewater from the South Shore Water Reclamation Facility, now discharged into Reynolds Channel, to the Cedar Creek ocean outfall, with the project expected to be fully operational by 2027. For a buyer, the first is a question for the seller: was an upgrade done, and under which program?

Suffolk runs its own sanitary code, and the county says nearly 70 percent of Suffolk homes use cesspools or septic systems (Suffolk County septic grants page). In the copy of Article 6 we found, amended in December 2020, replacing a cesspool or septic system for any permanent structure has needed county approval since 1 July 2019. Applications filed on or after 1 July 2021 for a new or expanded single-family house, or for a major reconstruction costing more than half the market value of the existing structure, must include an innovative/alternative (I/A) system where an individual system is allowed. An existing house that is not a major reconstruction, keeps its footprint and square footage and has five or fewer bedrooms is exempt. We could not confirm whether a like-for-like replacement of a failed cesspool must itself be an I/A system, so we do not say.

Article 19 of the code governs the I/A systems themselves (Suffolk County Sanitary Code, Article 19). The owner registers a new system before construction, re-registers it every 36 months and must hold a maintenance contract with a company holding a county liquid waste license, with service at least once a year. When a property with an I/A system changes hands, the seller must notify the county health department in writing and the new owner must register the system, each within 60 days. A buyer of such a house should ask for the registration and maintenance records. The county’s grant page lists a valid certificate of occupancy among the minimum requirements for an I/A grant. Babylon’s building department says the Town does not record where cesspools sit and that the Suffolk County Board of Health may be able to say (Town of Babylon).

Heating fuel: where oil is common and what an oil tank adds

The ZIP codes are examples chosen to show the range and are not a ranking; the county shares are in the first table. Our Nassau page has every Nassau ZIP we pulled.

The range is wide: 80% of homes in ZIP 11756 (Levittown) and 79% in ZIP 11967 (Shirley) burn oil, against 8% in ZIP 11561 (Long Beach). An oil-heated house has a tank, and the tank raises questions that a gas-heated house does not: where it is, how old it is and what became of it. DEC’s guide for homeowners (DEC’s homeowner guide to underground heating-oil tanks) makes four points. Most home tanks escape the State’s bulk-storage regulation because each holds under 1,100 gallons, and owners in Nassau, Suffolk and Westchester are pointed to their county health department. A 275-gallon steel tank was not designed to be buried and, left in place, will eventually corrode and leak. State law requires a heating-oil tank to be emptied, cleaned and purged of vapors. And when a house is sold, a bank or buyer will likely want an environmental assessment or the tank’s removal.

Suffolk adds its own layer. The county’s tank-registration page excepts only fuel-oil, kerosene and diesel tanks under 1,100 gallons used for on-site heating or intermittent power (Suffolk County Health Services), and Article 7 of its Sanitary Code adds rules for deep-recharge areas, so ask the county what applies to a particular tank. DEC’s open spill dataset lists 21,322 #2 fuel oil spill records for Suffolk in all years, 15,140 of them from private dwellings; they are reported spills, not confirmed tank failures (DEC spill incidents). We can describe the visible parts of a tank and its piping. The Standards do not require us to observe underground tanks (197-5.16), and a buried tank takes its own search; our oil tank guide sets out the options. The Levittown and Hicksville page goes further into the tank question for ZIP 11756, the most oil-heated Nassau ZIP we pulled.

Flood-insurance claims by named storm, and the storms that set Long Island’s rules

Two storms frame the rules. The National Weather Service describes the hurricane of 21 September 1938 as one of the most destructive and powerful in recorded history to strike Long Island and southern New England; it made landfall near Bellport as a Category 3 storm, sustained hurricane-force winds were felt across central and eastern Long Island, and around 60 lives were lost on Long Island (NWS New York, 1938 hurricane). Sandy, in 2012, dominates the flood-insurance file: the National Hurricane Center reports that around 100,000 Long Island homes were severely damaged or destroyed, primarily by storm surge and waves, with more than 2,000 deemed uninhabitable (NHC). In Suffolk, the weather service records that 29 people died at Westhampton Beach in 1938 and about 153 of its 179 homes were destroyed (NWS); in Sandy the National Hurricane Center measured a surge of 5.89 feet above normal at Montauk and a high-water mark of 5.6 feet above ground on Fire Island, and USGS recorded record coastal flooding in western Great South Bay and the Peconic Estuary (USGS).

FEMA’s National Flood Insurance Program claims file, which begins in 1978, attaches 51,523 claims to Nassau County and 33,936 to Suffolk. FEMA gives most claims an event name. Hurricane Sandy carries 26,964 of Nassau’s claims (52%) and 13,168 of Suffolk’s (39%); the first table sets the two counties side by side for the six largest event labels. Claims are not spread evenly. Six ZIP codes hold 31,734 of Nassau’s claims (62%) and six hold 15,480 of Suffolk’s (46%).

Among FEMA’s individual event labels, Hurricane Sandy is the largest in every ZIP code listed; the last column adds many labels together, so it can be larger. Each place name is the Postal Service’s mailing name for the ZIP code, not a village or hamlet boundary. Our Nassau page breaks Nassau’s ZIP codes down storm by storm. Claims are losses paid under a flood policy, so they exist only where the owner held a policy and filed; a ZIP with few claims is not necessarily dry. For comparison, ZIP 11530 (Garden City) has 19 claims and ZIP 11756 (Levittown) 16. The figures come from OpenFEMA, counted by the ZIP code on each claim.

On the buying side, treat the claims figures as a reason to ask and not a verdict, because a house far from the water may have no claims history simply because few neighbors held policies. Check the address on FEMA’s flood map, ask the seller whether the house has flooded and whether a claim was ever filed (the state’s statement asks both), and get an insurance quote early if the house is on or near a mapped flood zone. The inspection covers the grade, the foundation, visible water penetration and the sump pump; it cannot tell you the flood zone.

Cape, ranch, split-level and colonial: how house type changes the inspection

The census does not record architectural style, and we found no source for the share of Long Island houses by style, so we give none. The National Park Service’s study of postwar suburbs (NPS suburbs study) traces the sequence: Levittown’s 1947 Cape Cod, a one-and-a-half-story slab house with two dormers; a Ranch-like model by late 1949; then ranches and split-levels as the standard suburban house into the 1960s, with simplified Colonial Revival forms still popular. Each leaves a different trail. A Cape with a finished attic raises roof junctions, insulation and added wiring; a ranch with a basement recreation room raises moisture; a split-level adds stairs between levels and a lower floor close to the soil. Our Nassau County guide sets out the types in a table.

What the water-quality notices say

The numbers in the notices come from two layers of law. New York set maximum contaminant levels in 2020 of 10 parts per trillion each for PFOA and PFOS and 1 part per billion for 1,4-dioxane, and was the first state to set one for 1,4-dioxane (NYS Department of Health fact sheet). EPA’s April 2024 rule sets an enforceable limit of 4.0 parts per trillion for PFOA, with public water systems given until 2029 to implement solutions if monitoring shows levels above the limits; until then New York systems must still meet the state’s 10 parts per trillion. On 18 May 2026 EPA announced two proposed rules: one would keep the PFOA and PFOS limits but let systems request two more years, to 2031, and the other would rescind the limits for PFHxS, PFNA, HFPO-DA (GenX) and the hazard-index mixture (EPA’s PFAS drinking-water page). Both are proposals, not final. Private wells are outside these rules, which apply to public water systems.

A ZIP code does not tell you who supplies your water. USGS counts about 50 suppliers pumping from the aquifer across both counties. Separately, an archived 2025 copy of the Nassau County Department of Health’s page lists 46 public systems and roughly 500 private wells inside Nassau (Nassau County Department of Health). The two counts use different definitions and should not be added. Ask the seller who supplies the water, and read that supplier’s latest annual report, which lists what it found and the limit for each substance. Our Nassau page compares two village reports, and the Levittown and Hicksville page covers the Hicksville and Levittown districts.

In Suffolk, one report to ask about is the Suffolk County Water Authority’s (SCWA). Its 2026 edition, covering 2025, says the aquifer system is shallowest on the north shore, about 600 feet, and deepest on the south shore, about 2,000 feet, and that almost 70 percent of Suffolk community supply wells rate high or very high for susceptibility to nitrate (SCWA 2026 report). It reports 19 advanced-oxidation systems in service for 1,4-dioxane and a tool that shows a water quality report for the specific water delivered to a property (SCWA overview), and it says two wells were taken out of service for PFAS and that its naturally acidic groundwater is buffered with hydrated lime to prevent corrosion of home plumbing (SCWA treatment pages). Private wells are a different case. SCWA says virtually all private wells draw from the shallow glacial aquifer, New York does not regulate PFAS in private wells (NYS DOH); the Department of Health advises testing for bacteria at least once a year and for other contaminants every three to five years (NYS DOH), and the county runs a private-well testing program covering PFAS and about 300 other contaminants.

Termites and carpenter ants in older wood frames

New York law excludes pests from a home inspection (Real Property Law §444-b, in the Department of State’s compilation), so termites are a separate service (see our termite inspection page). Cornell’s NYS IPM adds that not all wood damage means a current infestation and that carpenter ants, which nest in wood weakened by moisture, signal a moisture problem (Cornell NYS IPM). A 2003 fact sheet from Cornell Cooperative Extension in Nassau says Long Island has one termite species.

Which code book governs new work: the 2025 Uniform Code

The code edition matters to your contractor and the permit office, not to the inspection. The Department of State’s notice says the amended Uniform Code and Energy Code took effect on 31 December 2025, that the Uniform Code replaced the 2020 edition with one that includes the 2025 Residential, Building and Plumbing Codes, and that building permit applications from that date must comply; the Energy Code has no transition period (the notice, in the Town of Cortlandt’s copy). It speaks of permit applications and, in the lines we read, says nothing about houses already built. Some local pages have not caught up: the Town of Hempstead’s flood page still cites the 2020 Residential Code for flood-zone construction, so ask which edition applies to your permit. The Standards bar us from deciding whether a house complies with codes (19 NYCRR 197-4.4).

Radon on Long Island: a low zone that still calls for a test

EPA’s county list puts Nassau and Suffolk in the lowest radon zone, Zone 3 (EPA radon zone data), which its New York map defines as a predicted average indoor level under 2 picocuries per liter; the same map still says to test every home (EPA’s map of radon zones for New York). The State Department of Health’s kit program, cumulative since 1987, found the State’s fix-it level of 4 picocuries per liter or more in 5.7% of 837 Nassau basements and 7.6% of 580 Suffolk basements (NYS DOH radon results by county). Another 30,000 to 40,000 tests a year in New York are done outside the program, so these are not the share of Long Island homes above the level. By statute a home inspection on Long Island, like any in New York, does not include radon, so it is a separate test; the State advises testing when buying a home (NYS DOH radon page). See our radon testing page.

Records to pull before you sign

On Long Island the building file for an address sits with a town, a village or a city, and which one depends on the address: some town rules stop at the edge of the incorporated villages, and each village or city keeps its own. Your attorney will order the municipal search, and you can prepare by knowing what to ask for.

Suffolk’s towns publish their own variants. Smithtown will search its records to see whether every permit has a certificate and offers a history letter, a letter in lieu, for houses built before permits were required in 1947 (Town of Smithtown). Southampton issues a pre-existing certificate of occupancy for structures that predate its zoning of 14 October 1957 (Town of Southampton). East Hampton’s research request form lets a buyer or seller ask for the final survey, a survey showing the well and septic locations, the property card, certificates of occupancy and open permits (Town of East Hampton), and Riverhead routes requests for copies through the Freedom of Information Law (Town of Riverhead). Babylon says a certificate of occupancy is what homeowner’s insurance and mortgage companies usually require when selling, buying or refinancing, and that structures not built to code may need repairs before a sale. We found no page in these towns that states a legal requirement for a resale inspection, and we did not check every incorporated village.

The seller’s property condition disclosure statement is the document to read first. By law it must be in the buyer’s hands before a binding contract is signed (Real Property Law §462). It records what the seller knows, not what an inspection would find: the seller need not investigate, an “as is” sale remains possible, and the form itself says it is no substitute for any home, pest, radon or other inspection. If you are the seller, read our page on a pre-listing inspection in Nassau County.

Where a home inspection on Long Island fits, and what it leaves out

In a New York purchase the lawyers go first, and the contract sets the inspection window. Once you hire an inspector, the Standards require a written pre-inspection agreement that describes the scope (197-4.2), and the licensing law gives the inspector up to five business days after the inspection for the written report, which is confidential and cannot be disclosed without your express consent (Real Property Law §444-g). The systems the Standards cover are listed in our guide to what a New York home inspection includes, and you can check any inspector’s license with the steps in our guide to verifying a license. The table sets what the Long Island records point to against what we look at and what the Standards leave out.

Frequently asked questions

About the figures on this page

• Housing age, heating fuel, building type and tenure come from the Census Bureau’s American Community Survey, 2020–2024 five-year estimates, for Nassau, Suffolk, New York State and the Suffolk ZIP codes shown. Estimates carry margins of error.
• Flood claims for Nassau and Suffolk are National Flood Insurance Program claims (version 3) from OpenFEMA, grouped by the ZIP code on each claim and by FEMA’s event label. They count insured losses only.
• Groundwater, aquifer and geology statements come from the USGS reports linked in the text; wastewater programs from the Department of Environmental Conservation; storm facts from the National Weather Service and the National Hurricane Center; drinking-water rules from EPA and the State Department of Health; radon results from the State Department of Health’s open data, cumulative since 1987.
• We read the statutes, rules and agency pages cited here in October 2026. They change, so check the current text.

More guides for Long Island

These pages go deeper on specific places and services under Long Island.

• Nassau County: Nassau County towns from Garden City to Massapequa: what is covered, what it costs and common conditions.
• Suffolk County: Suffolk County’s older, renovated and waterfront homes, foundations and drainage, specialty testing and cost.

Booking a home inspection on Long Island

Tell us the address, whether the house is on a sewer, a cesspool or a septic tank, and what heats it. We will say what we would look at first and which add-on tests suit the house, and if you already hold the seller’s disclosure statement, send it with your request.

The footer of every page prints our New York State license number. We work across both counties, the five boroughs and Westchester, and travel elsewhere on request; the walk-through can be in English, Urdu, Punjabi or Hindi.

To talk it over first, call 718-925-7071.