Areas we serve › New York City › Two- and three-family houses
Most people picture a house inspection as one family, one boiler and one electrical panel. In New York City that picture is the exception. Of the 637,938 residential tax lots the city classifies as one-, two- or three-family houses, 325,218 (51%) hold two or three homes. A buyer who walks into a two-family brick house in Brooklyn or a converted three-family in Queens is buying a small apartment building, and a two- and three-family home inspection should treat it like one.
This page explains how a two- and three-family home inspection differs from a single-family one, what each system looks like when it serves more than one household, and which questions the report cannot answer. The counts come from the city’s own property database, and the sources are listed at the end. Inspecwise is a New York State–licensed, InterNACHI-certified inspection business based in South Ozone Park, Queens, where about four in ten residential lots hold two-family houses.
Where the two- and three-family houses are
The table counts residential tax lots by borough from the Department of City Planning’s PLUTO file (version 26v2). It covers lots the city classifies as one-family (building class A), two-family (class B) or three-family (class C0). The last column is the share of those lots with a recorded year built before 1940, which is a helpful proxy for how old the systems inside may be.
| Borough | One-family lots | Two-family lots | Three-family lots | Share with two or three homes | Built before 1940 |
|---|---|---|---|---|---|
| Brooklyn | 61,349 | 94,710 | 34,174 | 67.8% | 70.9% |
| Queens | 150,637 | 96,302 | 23,991 | 44.4% | 50.2% |
| The Bronx | 21,413 | 29,465 | 11,092 | 65.4% | 45.9% |
| Staten Island | 76,985 | 31,349 | 872 | 29.5% | 20.1% |
| Manhattan | 2,336 | 1,867 | 1,396 | 58.3% | 92.4% |
Three patterns stand out. Brooklyn has the most two-family houses (94,710) and the most three-family houses (34,174), and about 70.9% of its small houses have a recorded build year before 1940. Queens has more one-family lots than any other borough (150,637), but also 96,302 two-family lots, and the city’s tax records classify 34,190 of them, 35.5%, as “two family converted from one family.” That is a far higher share than in Brooklyn (20.9%) or Staten Island (9.1%). Staten Island is mostly one- and two-family, with only 872 three-family lots, and the Bronx sits between Queens and Brooklyn.
A word on that “converted” label. It is a tax-classification code, not a legal finding. It tells you that at some point the house went from one family to two, and it does not tell you whether the work was permitted. We come back to that below.
What a two- and three-family home inspection adds
Four things separate these inspections from a single-family visit.
- Access. Every unit that is part of the sale needs to be reachable on the day: its kitchen, bathroom, panel, windows and heating equipment. When tenants live in some of the units, the seller or agent arranges entry and notice, and the report states which units were seen.
- Shared versus separate systems. One boiler may heat three apartments. Two apartments may share a drain stack, or one may be wired through the other’s panel. Working out which equipment serves whom is half the job.
- Time and sequencing. More kitchens, bathrooms, windows and outlets means more to test. We plan the visit around the number of units and the occupants’ schedules rather than treating it as a larger single house.
- The report is organized by unit. You need to know that the second-floor bathroom exhaust is not vented, and that it belongs to the second-floor apartment. A report that merges all of it into one list is hard to act on.
System by system, in a house with two or three homes
Heating and hot water
Most small multi-family houses in the city were built with one central boiler. Some have been split since, with a second heating system or electric heat added to a converted floor. We identify which equipment serves which unit, check that each apartment actually receives heat (zone valves, radiators or baseboard, thermostats), look at the boiler’s age, visible venting and safety devices, and note anything that looks wrong about a flue after a replacement. Hot water is its own question: a single large tank, an indirect tank off the boiler, a tankless unit or separate heaters per apartment each fail in different ways.
Fuel matters, too. In the Census Bureau’s 2020–2024 survey, 10% of Queens homes used fuel oil, against 73.8% on utility gas. A house still on oil may have an old tank in the basement, and a house that was converted to gas may have one that was abandoned. Our oil tank guide explains what to look for.
Electrical
Electrical is where multi-unit houses most often surprise buyers. We look for a service large enough for the number of apartments, a separate meter and panel for each household, and a house panel for shared areas such as the hallway and the boiler. In older houses we also check for wiring that has been extended through a wall into the neighboring unit, circuits that were added to a panel with no spare capacity, ungrounded two-prong outlets, missing GFCI protection near water, and panels from manufacturers with a history of breakers that fail to trip (Federal Pacific Stab-Lok and Zinsco are the usual examples). Houses wired in the late 1960s or early 1970s sometimes have aluminum branch wiring, which needs different connectors; an electrician should evaluate it if it turns up.
See the electrical inspection guide for what the inspector can and cannot judge from the panel cover.
Plumbing and drains
In a two- or three-family house the drain stack, the waste line to the street and sometimes the water supply serve every household, so a slow drain in one apartment can be a problem in the building. We run water in each unit, check pressure and flow at the fixtures, look for the leaks that show up as stains on the ceiling below, and note the supply and drain materials we can see: galvanized steel and cast iron are common in houses from the first half of the twentieth century and tend to corrode from the inside. The line from the house to the street is the part a visual inspection cannot see. A camera inspection of that line is often the most useful add-on in a multi-family house, because the line carries the waste of every unit. Our sewer scope guide describes the process.
Gas piping and appliances
Where each apartment has its own gas meter, we report the visible meters, shutoffs, connectors to ranges and dryers, and how dryers and water heaters vent. The state’s standards do not require an inspector to check gas supply piping, test for gas leaks or carbon monoxide, or determine whether there is enough combustion air, and gas-fired equipment in a basement apartment or an enclosed utility room raises exactly those questions, so they go to a licensed gas contractor. Anything that smells of gas or shows a flawed connection goes to the top of the report.
Roof, exterior and structure
Brick houses of the early twentieth century usually have flat or low-slope roofs. We look for ponding water, blistering, failed flashing at parapets, and downspouts that discharge against the foundation. On the facade we look at pointing, cracked or displaced lintels, the stoop and porch, the cornice, and the rear additions that were often built later than the main house. In the basement we check the foundation walls for cracking and moisture, the floor framing for notching or sagging, and whether a column or beam has been removed or replaced during a conversion.
Fire safety and ways out
A house with several households needs working smoke and carbon monoxide alarms in each of them, bedroom windows that open and are large enough to escape through, a clear route to the street from every apartment, and a basement or attic apartment with its own way out. We note what we see on the day. Whether a particular alarm layout meets the code that applies to that house is a question for the Department of Buildings and your attorney.
Problems that turn up in older multi-family houses
None of these is certain in any one house, and a newer or well-kept house may have none of them. They are the issues that repeat in older two- and three-family houses, which is why we look for them first.
| What shows up | Why it matters in a house with several homes | Who usually deals with it |
|---|---|---|
| One electrical panel overloaded by added apartments | Each added kitchen and bathroom adds load. Breakers get doubled up or oversized to stop them tripping | Licensed electrician |
| Boiler near the end of its life | It heats every unit, so a failure leaves several households cold, and replacement costs come out of one owner’s pocket | Heating contractor |
| Flat roof with ponding and tired flashing | Leaks reach the top-floor apartment first, then travel into the walls below. Tenants report stains before the owner sees the roof | Roofer |
| Basement apartment with moisture or a low ceiling | Damp finishes hide mold, and a low ceiling or a small window can make the space unusable as a home | Waterproofing contractor; your attorney and an architect for the legal question |
| Cast-iron stack or galvanized supply lines | A leak in a shared stack damages the units below, and the pipe is inside walls that belong to other households | Plumber |
| Gas appliances venting into the room | A flue that was disturbed during a remodel can leave carbon monoxide in the apartment | Gas-licensed plumber or heating contractor |
| Unpermitted work | A conversion done without permits can affect insurance, financing and the certificate of occupancy | Your attorney; an architect or expediter |
| Cracked brick, loose parapet or failing stoop | Falling masonry is a safety issue for everyone on the sidewalk, and repairs are a major cost | Mason; an engineer for larger problems |
Legal units and actual units
The most important question in a multi-family purchase is not on the inspection checklist. It is whether the number of homes in the house matches the number the city has on file.
In New York City the certificate of occupancy states the legal use of a building, including how many dwelling units it can have. A house sold as a “legal two-family” with a finished basement apartment, or as a “three-family” with a fourth kitchen in the attic, may be carrying a unit that the certificate does not allow. The citywide Building/Use complaint category in 311 includes “illegal conversion of residential building/space,” and in 2025 the system logged 8,097 such complaints in Queens. A complaint is only a report, and many are never confirmed, but it shows how often the question comes up.
An inspector can see the signs that a unit may not match the paperwork: an extra kitchen, a second set of meters or doorbells, a bedroom with no window, a basement apartment with a low ceiling, a stair added without a landing. We describe those in the report. We cannot decide whether work was permitted. That goes to the Department of Buildings’ online records, an architect or expediter if you need a professional opinion, and your attorney, who will ask for the certificate of occupancy and any open violations before you sign.
| What you want to know | Who can answer it | What the inspection adds |
|---|---|---|
| How many dwelling units are legal | The certificate of occupancy; the Department of Buildings’ records; your attorney | Notes anything in the house that suggests a different number of units |
| Whether a conversion was permitted | Department of Buildings permit and violation history for the address | Describes the quality and condition of the work that can be seen |
| Whether a unit is rent-regulated | The seller’s documents; state housing agency records; your attorney | Nothing. This is a legal and financial question |
| Whether the systems are safe and working | The inspection | Tests and describes each unit’s systems |
| What the repairs will cost | Contractor estimates you collect | Identifies what needs a specialist and how urgent it looks |
Tenants in the house
If the house is owner-occupied and you are buying it, the inspection looks like any other, with more apartments. If a tenant lives in one of the units, three practical points apply. Notice and timing are set with the seller or the agent, not by us. Furniture and stored belongings limit what can be seen, so the report notes areas that could not be reached or viewed. And if a tenant refuses entry altogether, the report says so, which is information for your attorney: a unit nobody has seen is a risk you may want the contract to address.
For buyers, our guide to the inspection contingency explains how the timing in the contract works, and why the days you are given to inspect matter more when there are several apartments to schedule.
Ask the seller before the inspection
A few documents save time on the day and tell you more than a visual inspection can. Ask your agent or attorney to request them early.
- The certificate of occupancy, and any permits for the conversion, the roof, the boiler or electrical upgrades.
- The age of the roof, boiler and water heaters, and any service records.
- Which utilities are metered separately and which are paid by the owner.
- Leases for any occupied unit, and whether anyone has reported heat, leaks or pests.
- Any history of sewer backups, basement flooding or insurance claims.
- Whether a unit has been renovated and who did the work.
Investor or owner-occupant: how to use the report
A two- or three-family house is both a home and a small business, and the report serves both purposes. Sort the findings into four groups. First, safety issues and active leaks. Second, systems at or near the end of their service life, such as a boiler, a roof or a water heater, which show up as large expenses over the next few years. Third, defects that affect a unit’s use, such as a window that will not open or a bathroom with no ventilation. Fourth, cosmetic items.
In New York the usual outcomes are a price reduction, a credit toward closing, a repair by the seller before closing, or walking away under the contingency. Which is available depends on the contract and on your lender, who may require specific repairs. Get contractor estimates for the large items before you negotiate, not after.
Two numbers an inspection cannot supply are the rent roll and the expected income. The report tells you what the building needs. Whether it pays for itself belongs to your accountant and attorney.
What happens on the day
A visit to a three-family house has the same shape as any inspection, with more rooms.
- Exterior and roof first. We walk the outside of the house, look at the roof from the ground and, where it is safe, from above or with a camera, and note drainage, facade and the condition of rear additions.
- Utilities and mechanical rooms. We find the meters, shutoffs, panels, boiler and water heaters, and work out which serve which unit.
- Unit by unit. In each apartment we test the fixtures, outlets, windows, doors, smoke and carbon monoxide alarms, and the heating, and look for water stains and signs of past leaks.
- Attic, basement and common areas. Framing, insulation, ventilation, stairs, railings and the route out of each unit.
- The walk-through. At the end we show you what we found, explain which items need a specialist, and answer questions on the spot. The written report follows, with photographs.
The state requires the written report within five business days of the inspection; ask what our timing is for your property when you book. See also how long a home inspection takes and what the report contains.
Add-on tests that suit these houses
| Test | Why it matters in a multi-family house | Read more |
|---|---|---|
| Sewer line camera inspection | One line carries the waste of every unit, and a failure affects all of them | Sewer scope guide |
| Oil tank inspection | Many older houses still heat with oil, and abandoned tanks turn up after conversions to gas | Oil tank inspection |
| Radon test | A basement or ground-floor apartment sits closest to the soil. The state’s definition of a home inspection leaves radon out, so it is always a separate test | Radon testing |
| Mold assessment | A basement apartment or a roof leak can leave moisture behind. Mold assessment is licensed separately by the state | Home mold inspection |
| Wood-destroying insect inspection | Termite damage is hidden in framing and often shared across attached houses | Termite inspection |
| Lead paint and asbestos sampling | Houses built before 1978 may have lead paint, and older boiler and pipe insulation may contain asbestos | Lead paint · Asbestos |
Where to read more
We inspect houses of this kind in Queens, Brooklyn and the Bronx, and we also inspect houses on Staten Island. For a neighborhood-level view, read our page for South Ozone Park, where roughly one residential lot in four is recorded as a two-family house converted from one-family. If you are selling, a pre-listing inspection in Queens lets you see the same issues before a buyer’s inspector does. Our home inspection report guide shows what you receive.
Every neighborhood and county page is listed on our areas we serve page.
Frequently asked questions
Is a two-family house inspection more expensive than a single-family one?
The scope is larger because there are more units, kitchens, bathrooms and systems to test, and the visit takes longer. Describe the property when you call or use the schedule form, and we will answer with a quote for that house.
Do all the apartments have to be open for the inspection?
Every unit that is part of the sale should be accessible. If one cannot be entered, the report says it was not inspected, and you should talk to your attorney about how the contract handles it.
Can the inspector tell me if the basement apartment is legal?
No. An inspector can describe what is visible, such as ceiling height, windows, exits and the condition of the wiring and plumbing, but legality depends on the certificate of occupancy and Department of Buildings records. Your attorney can check those.
What is a “converted two-family” in the city’s records?
It is a tax classification meaning the house was changed from a one-family to a two-family. It does not show whether the conversion was permitted or properly built.
Is it worth being at the house for the walk-through?
Yes, for at least the last hour. You will see how the systems are laid out and which equipment serves which apartment, which is hard to follow from a report.
Does the inspection include the sewer line?
A standard visual inspection looks at the visible drains and fixtures. The line from the house to the street needs a camera inspection, which we can add.
Do you inspect three-family houses?
Yes. The same process applies, with one more unit to test and a closer look at shared systems, fire safety and exits.
Can I get the findings explained in my own language?
We speak English, Urdu, Punjabi and Hindi, and we are happy to walk through the findings in any of them.
About the numbers on this page
- NYC Department of City Planning, PLUTO, version 26v2, through NYC Open Data. Counts are residential tax lots with at least one residential unit and building classes A (one-family), B (two-family) and C0 (three-family). Year-built values for older buildings are often rounded estimates, so we show shares built before 1940 and not an average.
- NYC Department of Finance building classification codes. Class B3 is described as “two family converted from one family.”
- NYC 311 service requests, counted for calendar year 2025. A 311 complaint is a report made by the public. It is not a violation.
- US Census Bureau, American Community Survey, 2020–2024 five-year estimates, house heating fuel for Queens County.
Booking an inspection with Inspecwise
If you are looking at a two- or three-family house, tell us how many units it has and whether any are occupied, and we will plan the visit around that. Our New York State home inspector license number, NYS LIC # 16000113811, is printed at the foot of every page, and this guide shows how to check it.
We work across all five boroughs, Nassau, Suffolk and Westchester, and travel beyond on request.
To talk it through first, call 718-925-7071.