Last edited 21 May 2018

Gross internal area GIA

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

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:

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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just a quick question, on a terraced house does GIA include the party walls?


I don't think so - It is the enclosed area of the building within the external walls (party walls would count as external walls). The Gross External Area would include the party wall - measured to the centre line of the wall.