NIA & GIA – What’s Included?

21st October 2022 | Dan Elliot

What is GIA and NIA and what is the difference?

 

Gross Internal Area (GIA)– is the area of a building measured to the internal face of the perimeter walls at each floor level. The building area is reported as the sum of all floor areas.

This includes all internal areas and features such as:

  • Columns
  • Toilets, shower rooms etc.
  • Voids over stairwells
  • Lift rooms
  • Corridors and circulation areas

The Areas of the building excluded for Gross Internal Area are:

  • Perimeter wall thickness
  • External balconies
  • Canopies

Gross Internal Area has several applications these are:

  • Building Cost Estimation
  • Valuation
  • Rating
  • Property Management/Service Charges

 

Net Internal Area (NIA) – is the usable area of a building measured to the internal face of the perimeter walls at each floor level. The building area is reported as the sum of all floor areas.

The areas included are:

  • Office/Workspace area
  • Areas occupied by nonstructural walls
  • Kitchens
  • Built in cupboards
  • Areas occupied by skirting and trunking

 

As NIA provides the usable floor area of a building it means that there are features and areas which must be excluded from the total floor area to calculate NIA. These include:

  • Entrance Halls used in common
  • Toilets, shower rooms etc.
  • Stairwells
  • Corridors and circulation used in common
  • Internal structural walls
  • Areas under 1.5m
  • Unusable areas which distance between opposite faces of walls is less than 0.25m
  • Heating and cooling apparatus extruding more than 0.25m into the usable area.