1 minute

For Business Rate purposes the net internal area (NIA) is the total usable area of each floor within a building, measured to the inside face of the boundary walls (ignoring skirting boards). Areas measured include:

  • kitchens
  • any built-in cupboards or units that occupy usable areas
  • perimeter skirting boards, mouldings and trunking
  • open circulation areas such as atria, corridors and entrance halls
  • Partition walls and other dividing elements

Areas that are excluded are:

  • internal structural walls
  • walls (whether structural or not) enclosing excluded areas
  • piers, columns, chimney breasts, ducts and other projections
  • cleaner cupboards
  • lifts, lift rooms, lift wells
  • stairwells and landings
  • stairwells, entrance halls, atria, landings and balconies used in common or for essential access
  • corridors and other circulation areas used in common with other occupiers or of a permanent essential nature
  • boiler rooms, fuel stores, plant rooms and tank rooms other than those of a trade process nature
  • car parking areas
  • spaces occupied by cooling and heating equipment, air conditioning systems and ducting which renders the space substantially unusable
  • areas with a headroom of less than 1.5m
  • toilets and associated lobbies, unless additional toilets have been installed
  • areas under the control of service or other external authorities

The net internal area (NIA) is used as part of the Business Rates Measuring Method.

Augment your Data

Our DoordaProperty product contains 357 data sources linked to 34 Million addresses. This includes information on residential, Commercial Property Internals and new builds.

Click for more info