ISO 4157 is an ISO standard for construction drawings and designation systems.

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"

Main definitions:

• 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

Standard samples:

00 Ground floor
05 5th floor
-2 2nd basement floor
#0215 2nd floor, room 15