Measurement examples

GIA is the area of a building measured to the internal face of the perimeter walls at each floor level

Included

• Areas occupied by internal walls and partitions
  
• Columns, piers, chimney breasts, stairwells, lift-wells, other internal projections, vertical ducts
  
• Atria and entrance halls with clear height above, measured at base level only
  
• Internal open-sided balconies, walkways    
  
• Structural, raked or stepped floors are to be treated as a level floor measured horizontally
  
• Horizontal floors, with permanent access below structural, raked or stepped floors
  
• Corridors of a permanent essential nature (e.g. fire corridors, smoke lobbies)
  
• Mezzanine floor areas with permanent access
  
• Lift rooms, plant rooms, fuel stores, tank rooms, which are housed in a covered structure of a permanent nature, whether or not above the main roof level
  
• Service accommodation such as toilets, toilet lobbies, bathrooms, showers and changing rooms
  
• Projection rooms
  
• Voids over stairwells and lift shafts on upper floors
  
• Loading bays
  
• Areas with headroom of less than 1.5m
  
• Pavement vaults
  
• Garages
  
• Conservatories
  

Excluded

• Perimeter wall thicknesses and external projections
  
• External open-sided balconies, covered ways and fire escapes
  
• Canopies
  
• Voids over or under structural, raked or stepped floors
  
• Greenhouses, garden stores, fuel stores in residential property
  

Note

Internal face means the brick/block or plaster coat applied to the brick/block work, not the surface of internal linings installed by the occupier.

Figure 3 Gross internal area