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 See also List of ISO standards 04157 Construction standards