It is composed of 3 parts:
- ISO 4157-1:1998 "Construction drawings -- Designation systems -- Part 1: Buildings and parts of buildings"
- ISO 4157-2:1998 "Construction drawings -- Designation systems -- Part 2: Room names and numbers"
- ISO 4157-3:1998 "Construction drawings -- Designation systems -- Part 3: Room identifiers"
- Floor n: is the horizontal partition between storey n and storey (n+1). The floor in storey 5 is named as floor 4.
- Room: identifiable physical space (area or volume, space or void) real or theoretical, although not necessary a traditional room (i.e., enclosed by walls, ceiling and floor).
- Room identifiers: registration number of spaces:
- Room numbers: numbers (code) of rooms
00 Ground floor 05 5th floor -2 2nd basement floor #0215 2nd floor, room 15