# What's the story with apartment numbers like "3G" and "5A"? Is it a NYC thing?

I lived in an NYC apartment that went Letter-Number, where the letter indicated the floor. It was very counter-intuitive and annoying for food deliveries. Fortunately, I lived in D-4 so I never had to explain that the entire fourth floor was “D.”

I stayed in an apartment in a building labelled like this in Calpe, Spain, in the early 90s. I think it was a rather tall building - at least 12 stories - but I don’t have a sense of how many apartments there were per floor. Quite a few, but probably not 26. It was a nice big place; three bedrooms plus a den, IIRC.

I see a few A and B apartments here in Montreal, but those seem to be to distinguish smaller apartments carved from larger homes, say a single-family building 1234 with a bachelor’s apartment built into the basement, it becomes 1234A and 1234B.

I lived in a dorm where each suite had a number, and each bedspace had a letter. For example I lived in a double suite with 3 other guys. The suite number was 312 (I don’t remember the exact number, but it was on the 3rd floor). When you walked in to the vestibule there were 4 doors (toilet, shower, and 2 bedrooms). The bedroom on the left had A&B the one on the right was D&C. The left side of each room was A or C, the right side B or D. I was D. It sounds strange, but each room had 2 phone jacks, 2 internet jacks, and 2 cable jacks. There was a set of jacks on both sides of the room and we had to order our own individual services from the University (cable was included in rent).

In my building in Toronto, the apartments start with 101 on the first floor, 201 on the second floor, and 301 on the third floor. The lowly basement dwellers get C1, B1, and A1.

Its a great system for construction and maintenance purposes.

Think of the building as a grid, where the floor number is the horizontal axis and the “line” letter, as it is called, is the vertical axis.

The plumbing, electrical and communication in these buildings is configured vertically and problems occur vertically…a plumbing problem in 10B is more likely to affect other"B" line apartments than other 10 floor apartments.

You will also notice buzzers and mailboxes configured around the vertical axis
1A
2A
3A
4A
1B
2B
3B
4B

Rather than

1A
1B
1C
1D
2A
2B
etc.

It’s much easier to wire the buzzer panel this way, because the wiring is vertical down each line rather than horizontal across each floor.

And as for the mailboxes, large buildings often have multiple zip+4’s…my 80 unit building has 8, and they are allocated by line…All the A+B apartments share a zip code, all the C+D apartments have the next zip, etc .

This is how the mailboxes (4 large banks of them located in a semi-public area) are arranged --and since the building is older than the zip code system I can only assume the mailbox layout dictated the zip code system – not the other way around.

Of course none of this really explains why letters and not a second set of numbers and all I can offer is that it is a lot clearer…Also I’ve never seen the letters I or O used as a line number and J is optional.

I lived in Spain for a while, over 30 years ago. The apartment building I lived in designated the apartments by number and then letter. So it’s not just a NYC thing, or even a US thing.

That apartment building also had a small grocery and deli on the ground floor, which was very convenient. All the Spaniards got a kick out of my heavily accented Spanish, because not only did I have an American English accent, when they were used to UK English accents, but I had learned Mexican flavored Spanish, since I took Spanish in Texas. So sometimes I was using the wrong word…sort of like lorry/truck and lift/elevator.

Where I grew up, the county roads parallel to the state line were numbered with the distance from that state line (26 Road, 30 Road, etc.). The roads perpendicular were lettered (A Rd, B Rd, etc), 1 mile apart between subsequent letters. For roads that ran between, they appended a fraction; e.g., I lived on a road called E 1/2 Rd. There were some roads (before subdivisions came in) named G 3/4, F 7/10, 29 1/2 Rd.

A few times, I got mail that had been misaddressed, but amazingly got delivered. I must’ve given my address over the phone as “E and 1/2”, and whoever transcribed it as “E.5”, which got delivered. Then somewhile later, someone read that as “East 5th Rd”, then “East Fifth St” (spelled out). It may’ve helped that we had a unique last name in the entire county.

In the UK you will sometimes see houses with a number and a letter. The usual reason for this is that a newer house has been built between two existing houses. So 31A would be located between 31 and 33. This also happens when an existing house has been subdivided into two or more flats.

Number for floor and letter for apartment is the norm through most of Latin America. In building complexes, there is also a letter first that indicates the building. So B-6-D means apartment D in floor 6 of building B.

I think it works better than using numbers for both floor and apartment when you normally have buildings with more than 10 floors and/or more than 10 apartments per floor. Is apartment 312 apartment 12 on the 3rd floor or apartment 2 on the 31st floor? You don’t know until you are at the building and see how it works. You know what 31B or 3L is before you get there and you don’t have to check anything once you do.

I live in flat 2/3 - i.e. the 3rd door (of 3) on the 2nd floor (3rd floor to Americans) but some databases can’t cope with calling it 2/3, so it’s also flat 6. (There are no flats on the ground floor)

Confusingly (especially for new postmen) the ground floor does have two doors that look like front doors (but are side doors into the stair from the maindoor flats on either side) so our door is actually the 8th door you come to!

Grand Junction/Fruita CO?

In Chicago, I’ve lived in buildings with letter-number and with number-letter combos (the first being the floor, the second being the unit). I lived in 3D for awhile, then I moved to B-52!

Most high rise condo / apartments I’ve seen across the US use the floor/unit = number/letter method. Not so much in low-rise 2 and 3 story facilities.

8A or 23-J would be very typical unit identifiers.

I lived in a SoCal apartment complex once with multiple small buildings on the site, so the buildings were given a letter and the units got a number. 6G is building G, unit 6.

I was in 14-B3 in my last apartment before buying a house.

Building 14, B for the second floor and Apartment 3.

Most apartments are multilevel, and the numbers refer to the level; my apartment was multi-building and the numbers referred to building. FWIW I lived on Eastern Long Island (suburbs).

For the building in which I live, in Busan, it’s a tax dodge. It’s a four-floor building and each floor has five apartments. The problem with that, though, is there’s a higher tax for the building owner to pay if there are more than 19 apartments in the building. The dodge is to put a foyer in front of the last two apartments on the fourth floor. The foyer is the entry to Apartment 404 and the nurse next door to me lives in Room 404A while I live in Room 404B.

It’s the usual scheme in Spain. My mother’s flat is 9B; mine is 3B; Middlebro lives at 3B; Lilbro at 1A (not in the same building). The number is the level, the letter is the door. If there are only two doors, they may be called “left” and “right” instead.

Exactly! Over by Central High School.