Gross external area GEA

The area of a building can be measured in a number of different ways:

• Gross external area (GEA).
• Gross internal area (GIA).
• Net internal area (NIA).

It is very important to be clear about which measure is being used, for example in property sales, planning applications, building regulations applications, lease negotiations, rating valuations and so on.

The UK government's Valuation Office Agency (VOA) Code of measuring practice: definitions for rating purposes suggests that 'gross external area' refers to the whole area of a building taking each floor into account, including perimeter walls. This includes:

• Perimeter wall thickness and external projections.
• Areas occupied by internal walls (whether structural or not) and partitions.
• Atria and entrance halls, with clear height above, measured at base level only.
• Columns, piers, chimney breasts, stairwells, lift wells, and so on.
• Lift rooms, plant rooms, tank rooms, fuel stores, whether or not above roof level.
• Any area with a headroom of less than 1.5m.

Gross external area excludes:

• Open balconies.
• Open fire escapes.
• Open sided covered ways.
• Open vehicle parking areas, terraces and so on.
• Canopies.
• Voids over or under structural, raked or stepped floors.
• Greenhouses, garden stores, fuel stores, and the like in residential property.
• Any area under the control of service or other external authorities.

It suggests that party walls should be measured to their centre lines.

According to NRM1: Order of cost estimating and cost planning for capital building work, the gross external area is '...the area of a building measured externally (i.e. to the external face of the perimeter walls) at each floor level. The rules of measurement of gross external floor area are defined in the latest edition of the RICS Code of Measuring Practice.' NRM1 was republished in a new edition in October 2021 and reissued, unchanged, as RICS professional practice information in October 2022.

The RICS Code of Measuring Practice, 6th edition (2007, amended 2015), on which the VOA's rating definitions were originally modelled, has since been superseded for general RICS practice by RICS Property Measurement, 2nd edition, which became mandatory for all RICS members and regulated firms on 1 May 2018 and aligns with the International Property Measurement Standards (IPMS). The VOA's own definitions for rating purposes, set out above, remain in force in their own right and continue to apply for rating valuations, other than, areas with a headroom of less than 1.5m which are excluded from the VOA measurement.

[edit] Related articles on Designing Buildings Wiki

• Area.
• Floor area ratio.
• Gross development area.
• Gross internal area.
• Gross site area.
• International Property Measurement Standards.
• Measurement.
• Net internal area.
• Site area.
• Total useful floor area.