Storey - Room Numbering

Room Numbering

In modern buildings, especially large ones, room or apartment numbers are usually tied to the floor numbers, so that one can figure out the latter from the former. Typically one uses the floor number with one or two extra digits appended to identify the room within the floor. For example, room 215 could be the 15th room of floor 2 (or 5th room of floor 21), but to avoid this confusion one dot is sometimes used to separate the floor from the room (2.15 refers to 2nd floor, 15th room and 21.5 refers to 21st floor, 5th room) or a leading zero is placed before a single-digit room number (i.e. the 5th room of floor 21 would be 2105). Letters may be used, instead of digits, to identify the room within the floor—such as 21E instead of 215. Often odd numbers are used for rooms on one side of a hallway, even numbers for rooms on the other side.

An offset may be used to accommodate unnumbered floors. For example, in a building with floors labeled G, M, 1, 2, ..., 11 and 12, the 4th room in each of those floors could be numbered 104, 114, 124, 134, ..., 224, and 234, respectively — with an offset of 11 in the floor numbers. This trick is sometimes used to make the floor number slightly less obvious, e.g. for security or marketing reasons.

In Portugal, the rule (official standard) is:

1. In buildings with only two sides, all the apartments are marked as Esq. (Esquerdo = Left) or Dto. (Direito = Right). So we have C/V Esq. (Underground Floor Left), R/C Esq. (Ground Floor Left), 1º. Esq (1st Floor Left), etc.; and C/V Dto. (Underground Floor Right), R/C Dto. (Ground Floor Right) 1º. Dto. (1st Floor Right), etc.
2. Buildings with more than two apartments per floor, are marked with letters, clockwise within each deck. So apartment 8º-D (not 8D) means the 8th floor (hence the character "º" meaning ordinal number), apartment D (counting in clockwise direction, for those who are in the floor entrance). But a very common form for buildings with three apartments per floor is, Esq.-Frt./Fte. (Frente, en: Front - for the apartment located between left and right)-Dto.

These two rules, universally adopted, made many things easy, namely for blind people, who don't need to ask where is the apartment "X".