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Room Numbering

• Introduction
• Floor numbering
• Room numbering
• Numbering systems and scheduling
• Client requirements
• Late changes

Introduction

• This page describes a system for the numbering of floors and rooms on projects of varying size and complexity. The recommendations are based on BS EN ISO 4157-2 and the practical experience of several architectural practices.
• This page should be read in conjunction with the page on Door Numbering.

Floor numbering

• It is recommended that a floor level numbering system is established, starting from the lowest level. All basement and roof levels should be numbered. This system may be independent of the everyday naming of floors and levels.
• Two logical systems:
• Every level is numbered consecutively starting from the lowest level. For example:
  Lower Basement - Level 1, or 01.
  Basement - Level 2, or 02.
  Ground Floor - Level 3, or 03.
  Mezzanine - Level 4, or 04.
  First Floor - Level 5, or 05.
  Second Floor - Level 6, or 06.
  etc.
• 'Main' levels form a logical sequence with 'minor' levels interspersed. For example:
  Lower Basement - Level 05.
  Basement - Level 10.
  Ground Floor - Level 20.
  Mezzanine - Level 25.
  First Floor - Level 30.
  Second Floor - Level 40.
  etc.
• Read about Numbering systems and scheduling.

Room numbering

Principles

• BS EN ISO 4157-2 requires that the numbering should be logical and, preferably, consecutive (on each floor).
• Three logical systems - select whichever is most appropriate for your project:
• Rooms are numbered starting from the main entrance to the building, or the main access to each floor, and progressing clockwise.
• In buildings such as hotels, where such a numbering system is conventional, rooms may be numbered in an ascending order on both sides of a corridor in a zig-zag manner (BS EN ISO 4157-2, clause 4.5.1).
• If there is no logical starting point, rooms should be numbered starting from the top-left-hand corner of the complete floor plate drawing (Location or General Arrangement drawing as appropriate), and progressing clockwise.
• You should number all rooms, corridors, and ancillary spaces such as ducts and staircases. Small spaces wholely within another room, such as built-in cupboards, may be omitted from the consecutive sequence and given the number of the room in which they are located, plus a suffix.

Numbering rules

• Numbers should start with the Floor Number and have as many digits as necessary. BS EN ISO 4157-2 recommends that three digits (one for the floor and two for the room) should be considered normal, i.e. unless the building is very large or very small. For example:
  Ground Floor - Rooms 301 to 399
  First Floor - Rooms 501 to 599
• BS EN ISO 4157-2 (clause 4.4.2) recommends that no rooms are numbered zero, i.e. **0 or ***0 should not be used.
• Large buildings may require four or five digits and this will need co-ordination with the Floor Numbering system. For example:
  Floors numbered with two digits, up to 99 rooms per floor:
  Ground Floor - Rooms 2001 to 2099
  First Floor - Rooms 3001 to 3099
  Floors numbered with two digits, over 99 rooms per floor:
  Ground Floor - Rooms 20001 to 20999
  First Floor - Rooms 30001 to 30999
• Small buildings may be more sensibly numbered with two digits. For example:
  Ground Floor - Rooms 11 to 19
  First Floor - Rooms 21 to 29
• For buildings with repetitive floors, it is recommended that room numbers are repeated by floor. For example:
  Plant room on First Floor - Room 317
  Equivalent plant room on Second Floor - Room 417
  Equivalent plant room on Third Floor - Room 517
• Read about Numbering systems and scheduling.

Numbering systems and scheduling

• Those considering a departure from the numbering systems described above, in particular the use of 'B' for Basement, 'G' for Ground Floor, etc. should be reminded that this will cause problems with computer-based scheduling systems ('F' will sort before 'G' for example).
• Those using computer-based scheduling systems may wish to consider 'padding' numbers with leading zeros for overall consistency and easier sorting, e.g. 1 can become 01 or 001 or 0001 dependant on whether the highest room number is 99, 999, or 9999. You will need to consider this before putting the room numbers on the drawings.

Client requirements

• Some clients will have their own numbering systems which may be incompatible with these recommendations - few clients number or name every uninhabitable space, for example.
• Establish whether a client numbering system exists as early as possible during the project and, more particularly, whether it is a client requirement that their system is used throughout the design and construction process. This is, for example, a common requirement on projects for some government departments.
• It is almost inevitable that the client's system will be less satisfactory for construction purposes than the numbering systems described above. Explain the benefits of the BS EN ISO 4157-2 system and try to convince the client to allow the use of the system described on this page during the construction process.
• It is not uncommon for architects to be asked to reconcile the numbering systems used during construction with the client's proposed system before Practical Completion. The effort involved should not be under-estimated, particularly on larger projects, and may justify an additional fee if the client request for such reconciliation is made at a late stage in the project.

Late changes

• However much planning is carried out, late changes to room numbers are inevitable. BS EN ISO 4157-2 recommends:
• When a room is added, it should take the next available unused room number on that floor, even though this will not place the room in a logical order.
• When rooms are combined, the resulting room should always take the lowest number, leaving the higher number(s) unused.
• When a room is split into two or more rooms, one of these should retain the original number and the others should take the next available unused room numbers on that floor, even though this will not place the rooms in a logical order. For example:
  Assume a floor of 53 rooms, numbered 2001 to 2053. Room 2021 is subdivided into two at a late stage. The two 'new' rooms would be numbered 2021 and 2054.
• Some architects prefer to give new numbers to all resulting rooms to prevent confusion - BS EN ISO 4157-2 is "silent" on this option. For example:
  Assume a floor of 53 rooms, numbered 2001 to 2053. Room 2021 is subdivided into two at a late stage. The two 'new' rooms would be numbered 2054 and 2055, leaving 2021 unused.
• An alternative system is to use suffixes to maintain the 'logical' sequence. This does not comply with BS EN ISO 4157-2 but may have advantages in certain situations. For example:
  Using the above example, the two 'new' rooms would be numbered 2021A and 2021B.

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