NYC apartment terms: junior 1, flex 2, railroad, convertible
What NYC listing jargon means: junior 1, flex 2, convertible, railroad, alcove studio, floor-through, prewar, walk-up. Plus what makes a room a legal bedroom.
7 min read · Updated
A junior 1 is usually a studio with a small separate sleeping or living nook; a flex 2 is a one-bedroom with a living room big enough to wall off as a second bedroom. Neither term has a legal definition, so the only way to know what you're getting is to look at the floor plan and check whether each "bedroom" has a legal window.
NYC listings use a shorthand that can confuse anyone new to the city, and some of it hides real trade-offs: a "convertible" needs a wall you may not be allowed to build, and a "railroad" means walking through one bedroom to reach another. Below is a plain-English glossary, followed by the state rules that decide whether a room can legally be a bedroom.
Legal bedroom basics (apartment buildings built after April 18, 1929)
- Window area
- ≥ 1/10 of floor area
- Each window at least 12 sq ft (MDL §30(8))
- Window must open onto
- Street, yard or court
- Not a hallway or another room
- Minimum room size
- 80 sq ft
- Post-1929 buildings (MDL §31)
- Ceiling height
- 8 ft minimum
- Post-1929 buildings (MDL §31)
NYC apartment terms glossary
These are the meanings most brokers and landlords use. Usage varies, and none of these labels is checked by any agency, so always ask for a floor plan with dimensions.
| Term | What it usually means | What to check |
|---|---|---|
| Studio | One main room for living and sleeping, plus a kitchen (often along one wall) and a bathroom. | Closet space; whether the kitchen is open to the bed area. |
| Alcove studio | A studio with an L-shaped nook off the main room, often big enough for a bed. | Whether the alcove has its own window. |
| Junior 1 (Jr 1) | A large studio with a separate area, sometimes a small room without a door or full wall, for sleeping or dining. | Is it a real room? Many junior 1s are legally studios. |
| Convertible / Convertible 2 | A studio or one-bedroom with a space that could be walled off into an extra room. | Whether the landlord allows a wall, and whether the new room would have a legal window. |
| Flex 2 / Flex 3 | A one- or two-bedroom whose living room is big enough to partition into one more bedroom. | Same as convertible, plus whether you lose your only living space. |
| True 2 / True 3 | Each advertised bedroom is a separate room with a door and a window. | Measure: tiny “true” rooms still exist. |
| Railroad | Rooms in a straight line, one opening into the next, often with no hallway. | Privacy: someone may walk through your bedroom. |
| Floor-through | One apartment takes up the whole floor, with windows front and back. | Light and cross-ventilation are usually good. |
| Duplex / Triplex | One apartment on two or three levels connected by internal stairs. | Stairs, and whether lower levels are legal living space. |
| Garden apartment | Ground-floor or lower-level unit with access to a yard. | Whether it is partly below ground; see basement rules. |
| Classic six / Classic seven | Traditional prewar layout: living, dining, kitchen and bedrooms, one often a small staff room. | Size and window of the small room. |
| Loft | Open, high-ceilinged space, often in a converted commercial building. | Legal residential use on the certificate of occupancy. |
| Prewar / Postwar | Usually built before or after World War II. No legal definition. | Year built on the building’s record. |
| Walk-up | Building with no elevator. | Which floor; DOF codes walk-ups as class C. |
| Elevator building | Building with at least one elevator. | DOF codes elevator apartments as class D. |
| Pressurized / temporary wall | A wall wedged in place without screws to split a room. | Landlord permission, and whether the new room meets light, air and exit rules. |
What makes a room a legal bedroom in NYC?
For apartment buildings, the main rules are in New York's Multiple Dwelling Law, which applies to buildings rented or occupied as the home of three or more families. The law treats any room used for sleeping as a "living room", so the light, air and size rules for living rooms apply to bedrooms too.
1. A window to the outside
In multiple dwellings built after April 18, 1929, MDL §30 requires every room to have at least one window opening directly onto a street, or onto a legal yard, court or space above a setback. The total window area must be at least one-tenth of the room's floor area, and each window must be at least 12 square feet. At least half of the required window area has to open; if the room has a mechanical ventilating unit supplying at least 40 cubic feet of air per minute, the window only needs to open to a quarter of its area (and at least 5.5 square feet). Older buildings, such as tenements, fall under other parts of the law with their own light and air rules. A window onto another room, a hallway or an interior airshaft that isn't a legal court does not count.
2. Minimum size and ceiling height
In multiple dwellings built after April 18, 1929, MDL §31 requires every living room (including bedrooms) to have at least 80 square feet and to be at least 8 feet across at its narrowest point. In apartments with three or more bedrooms, up to half the bedrooms may be 7 feet wide. Each apartment in a class A building must have at least one room of 132 square feet or more, and every room must be at least 8 feet high.
Some rules apply to every multiple dwelling, whatever its age. MDL §31(6) limits a room to sleeping no more than two adults (children 12 and over count as adults; two children aged 2 to 11 count as one adult; children under 2 are not counted). It also requires at least 400 cubic feet of air per adult and 200 per child in every room, and sets a floor of 60 square feet and 6 feet across for any living room.
3. A way out
A room created with a temporary wall can cut off the path to the apartment's exit or fire escape window, or block a sprinkler head, and the new room still needs its own legal window. If you are considering a flex apartment, ask the landlord in writing whether walls are allowed and what conditions apply.
One- and two-family houses fall under different code rules than the Multiple Dwelling Law. If you are renting a room in a house, the window-and-size tests above are still a good practical guide, but ask the owner or check the certificate of occupancy for the legal number of units.
How to compare listings with different labels
- Count legal bedrooms, not advertised ones. A "flex 3" with two legal bedrooms is a two-bedroom with a big living room. Compare its rent with other two-bedrooms.
- Price per bedroom matters for shares. If roommates will each take a room, use the roommate rent split calculator to weight rent by room size and features.
- Walk-up floor changes the value. A fifth-floor walk-up costs you every day you carry groceries or a stroller. The building's class on its Roofy building page tells you whether it is a walk-up (class C) or elevator building (class D). See NYC building class codes.
- Year built hints at layout. Prewar buildings often have railroad or classic layouts and thick walls; the building page shows the year built.
- Who can live there is a separate question. New York's roommate law (Real Property Law §235-f) controls how many unrelated people can share a lease; see New York roommate law.
Questions to ask about any layout
- Can I see a floor plan with room dimensions?
- Which rooms have windows, and what do those windows face?
- Is a temporary wall allowed? Who installs it, who pays, and does it have to come down when I leave?
- Is this unit listed with the same number of rooms on the building's legal paperwork?
- For railroads: can each bedroom be closed off with a door?
Then tour it with the apartment viewing checklist, and check whether you meet the income rule with the 40x rent guide.
Listing terms (junior 1, flex, convertible, railroad, etc.) are industry jargon with no legal definition; definitions describe common usage and are flagged as such. Re-verified 2026-10-12 on nysenate.gov: MDL §4(7) multiple dwelling = 3+ families; §4(18) sleeping rooms are living rooms; §30(1) applies to multiple dwellings erected after April 18, 1929; §30(2) window onto street/yard/court; §30(8)(a)-(c) 1/10 window area, 12 sq ft each, half openable or 25% (min 5.5 sq ft) with 40 cfm mechanical ventilation (corrected: earlier text implied no opening was needed with ventilation); §31(2) 132 sq ft room in class A, 80 sq ft, 8 ft high, 8 ft least dimension, 7 ft for up to half the bedrooms in 3+ bedroom units; §31(6) two-adult sleeping limit, 400/200 cubic feet, 60 sq ft / 6 ft minimums. Added post-1929 qualifiers. Softened the temporary-wall paragraph to practical risks (no specific code section cited). DOF building class C = walk-up apartments, D = elevator apartments, verified on the DOF code list.
Sources
- NY Multiple Dwelling Law §4 (definitions: "living room" includes rooms used for sleeping) · New York State Senate (accessed October 12, 2026)
- NY Multiple Dwelling Law §30 (windows, light and ventilation) · New York State Senate (accessed October 12, 2026)
- NY Multiple Dwelling Law §31 (room sizes, ceiling height, occupancy) · New York State Senate (accessed October 12, 2026)
- Building Classification codes · NYC Department of Finance (accessed October 12, 2026)
- NY Real Property Law §235-f (roommate law) · New York State Senate (accessed October 12, 2026)
General information, not legal, tax or financial advice. Rules change; confirm with the agency or a professional before you act.