Measuring Gross Internal Area (GIA) for the Community Infrastructure Levy (CIL)

Developments which create one or more new dwellings (including replacement dwellings), or involve the creation of more than 100 square metres of new build floor space, will be liable for CIL. Retail development of 100 square metres or more will also be CIL liable.

Therefore, to determine whether a development is liable for CIL and the amount of CIL we need to charge, we will calculate the 'gross internal area'.

In addition, floor areas proposed to be retained (converted) or lost through demolition may be used to reduce the CIL liability. In order for the liability to be reduced, it must be satisfactorily demonstrated that the existing floor space has been in continuous lawful use for a period of at least six continuous months in the three years before planning permission is granted.

You can find out more about the charges for CIL on our 'chargeable development types' page and our charging schedule, rates, instalments and payments page.
 

How we calculate GIA

To calculate GIA, we use the RICS Code of Measuring Practice guidance. This states that: "gross internal area is the area of a building measured to the internal face of the perimeter walls at each floor level."

When calculating GIA, we include:

• internal walls
  • including party walls in the case of adjoining new houses
  • walls between main living spaces and integral garages
• floor space into doorways
• areas exposed by removing walls
• areas under 1.5 metres in height
• areas underneath stairs
• garages
• car ports with two or more walls
• undercroft parking
• useable space with permanent access (for example, loft conversions)
• balconies and porches enclosed on three sides