Estates management record 2013/14
Gross Internal Area and Net Internal Area
Version 1.0 Produced 2014-08-15
Gross Internal Area (GIA)
GIA is the total area of buildings owned, occupied or maintained by the HEP, measured to the internal face of the perimeter walls at each floor level (i.e. the footprint of the building excluding the width of the outside walls). It includes areas occupied by internal walls and partitions.
Net Internal Area (NIA)
NIA is the usable area within a building measured to the internal face of the perimeter walls at each floor level. NIA covers all areas which are used for a specific purpose.
- teaching and research rooms,
- built-in units, cupboards etc. occupying the useable area,
- academic stores,
- changing rooms and showers (e.g. within or as part of clean rooms, catering facilities, sports facilities),
- porters' offices and kiosks,
- first aid rooms,
- staff common rooms,
- internal partition walls (e.g. fixed walls, de-mountable re-moveable screens),
- ramps of lightweight construction to false floors,
- a floor area which contains a ventilation/heating grill,
- area occupied by skirting and perimeter trunking,
- areas served by internal non-structural walls, de-mountable partitions (whether or not permanent) etc. where the purpose of the division is partition of use (and not support) provided the area beyond is not used in common (by more than one occupier),
- pavement vaults,
- notional lift lobby and similar areas, where there are several functions using the area, such as meeting space, reception, or cafe,
- accomodation on NHS sites which is maintained or paid for.
It does not include those parts of buildings which enable them to function, such as corridors. These are classified as balance areas.
Approaches for defining NIA
There are two alternative approaches for the return of data on NIA:
- NIA Royal Institution of Chartered Surveyors (RICS) basis,
- NIA room area.
1. NIA RICS basis
The NIA RICS definitions are contained in the 'Code of Measuring Practice: A Guide for Property Professionals' (Sixth Edition), published by the RICS. This method involves the measurement of the internal room area part way into the width of internal walls and partitions.
This is the prefered method of measurement and is demonstrated by the left-hand room in the diagram below.
2. NIA room area basis
This method involves the measurement of the internal room area less the width of internal walls and partitions.
This is the less preferred method of measurement and is demonstrated by the right-hand room in the diagram below.
What are balance areas?
Balance area is the floor area provided as part of the GIA to enable the building to function.
Balance area should be excluded from the NIA calculations.
The following are examples of balance areas:
- corridors and other circulation areas of a permanent nature (e.g. fire corridors, smoke lobbies etc.),
- internal open-sided balconies or similar,
- internal structural walls, walls enclosing excluded areas, columns, piers, chimney berasts, vertical ducts, and other projections,
- stairways and stairwells (and voids over),
- entrance lobbies (where the function is solely or primarily for entry/circulation),
- foyers (where the function is solely or primarily for entry/circulation),
- atria with clear height above, measured at base level only (where the function is solely or primarily for entry/circulation),
- permanent lift lobbies, permanent lift rooms, liftwells, and lifts (and voids over),
- lavatories and toilet lobbies,
- cleaners' stores,
- cleaners' cupboards (as defined in the RICS definition),
- covered areas (e.g. plant rooms, tank rooms, fuel stores which are housed in a structure of a permanent nature, whether or not above main-roof level,
- loading bays,
- permanent and continuous air-conditioning, heating, or cooling apparatus (as defined in the RICS definition),
- boiler houses,
- calorifier chambers,
- fuel stores.
Therefore in the diagram below the balance area is that which is not contained within the red box. The area contained within the red box is eligible for inclusion within NIA. The area lying outside of the red box is excluded, i.e. the corridor and lavatory.
Contact Liaison by email or on +44 (0)1242 388 531.