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Last edited 21 May 2018
Gross internal area GIA
The area of a building can be measured in a number of different ways:
- Gross external area (GEA).
- Gross internal area (GIA) or gross internal floor area (GIFA).
- Net internal area (NIA).
It is very important when describing the area of a building to be clear about which measure is being used, for example in planning applications, building regulation applications, property sales, 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 internal area includes:
- Areas occupied by internal walls (whether structural or not) and partitions.
- Service accommodation such as WCs, showers, and changing rooms.
- Columns, piers, whether free standing or projecting inwards from an external wall, chimney breasts, lift wells, stairwells and so on.
- Lift rooms, plant rooms, tank rooms, fuel stores, whether or not above roof level.
- Open-sided covered areas (should be stated separately).
Gross internal area excludes:
- Open balconies.
- Open fire escapes.
- Open-sided covered ways.
- Open vehicle parking areas, terraces and so on.
- Minor canopies.
- Any area with a ceiling height of less than 1.5m (except under stairways).
- Any area under the control of service or other external authorities.
The VOA code 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.
NB, NRM1: Order of cost estimating and cost planning for capital building work, defines ‘gross internal floor area’ (GIFA) (or gross internal area (GIA)) as:
‘…the area of a building measured to the internal face of the perimeter walls at each floor level. The rules of measurement of gross internal floor area are defined in the latest edition of the RICS Code of Measuring Practice.’
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