External perimeter of building measured to the outside face of the external walls on the ground floor. If the upper floors have a different plan shape/size to the ground floor enter the average length of the perimeter for the ground and upper floors. External walls are defined as walls which have one face on the outside of the building and include both skins of hollow or composite external walls - measure only the outer skin.

Total area of all floors measured inside inner face of external walls measured over voids stairwells and walls