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.'
The VOA Code of measuring practice is in general agreement with RICS Guidance Note, A guide for Property Professionals, 6th Edition Code of measuring practice 2007, other than, areas with a headroom of less than 1.5m which are excluded from the VOA measurement.
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