Overview
ISO 4157-2:1998 - Construction drawings - Designation systems - Part 2: Room names and numbers - specifies rules for assigning and showing room names and room numbers on building drawings and for everyday identification of rooms, zones, spaces and voids. It is part of the ISO 4157 series that standardizes designation of buildings, rooms and piece identifiers. The standard is intended for routine building use; project-wide identification through design, construction and maintenance is covered by ISO 4157-3.
Key topics and requirements
- Logical numbering order: Assign numbers to all rooms on each level in a logical, preferably consecutive order, starting with n01 (where n = level number). Numbers may apply to exterior or covered zones (e.g., pool, garage).
- Separate buildings: Number rooms independently in each building included in a project.
- Presentation on drawings:
- Write room names and numbers inside each room on the drawing.
- Underline names and numbers on drawings for clarity; do not underline physical door signage.
- Small rooms may show only numbers on drawings; names should appear in a table on the same sheet unless a symbol clearly indicates use (toilet, sink, cloakroom).
- Number format rules:
- Prefer two-digit room numbers preceded by the level number (examples: 101–199, 201–299, 301–399).
- Avoid using a zero room number at any level; numbers like 20, 300 or 4000 are reserved to represent the exterior (the “PIÈCE 0” concept).
- Four-digit numbers must contain no spaces or punctuation.
- Alphanumeric prefixes (R01, C02, M03, S04) are allowed for mezzanines, basements, cellars, etc.
- Numbering direction and conventions:
- Number rooms to aid orientation (commonly clockwise from main entrance) or follow a logical local convention (e.g., hotel zigzag numbering).
- Omitting ranges for clarity or future reserve is permitted.
- Vertical shafts (stairwells, lifts) should keep consistent numbers across levels where possible.
- Modifications:
- New rooms added late can take the next unused number for the floor.
- When rooms are merged, the resulting room keeps the lowest original number.
- Small spaces (closets) may use the host room number with a lowercase suffix.
Applications and users
This standard is directly useful to:
- Architects and architectural drafters producing construction drawings
- BIM modelers and CAD managers implementing room numbering conventions
- Facility managers and building owners for consistent room identification
- Contractors, signage specialists and maintenance teams for site labeling and documentation
- Fire safety planners and emergency services for clear spatial referencing
Keywords: ISO 4157-2, room numbering, room names and numbers, construction drawings, designation systems, architectural drawings, facility management.
Related standards
- ISO 4157-1:1998 - Buildings and parts of buildings (reference for level numbering)
- ISO 4157-3 - Identifiers of rooms (for project identification across design, construction and maintenance)
