Measuring Your House

You need to find the gross external floor area (GEFA) of your house – both upstairs and downstairs. GEFA is defined as the area of a dwelling measured externally at each floor level.

The best way is to go outside and measure the length and width of your house and multiply those figures together. If you cannot measure outside, measure inside and add the thickness of the walls. You can measure either in feet or metres. An integral garage would be included in this calculation. You now know the ground floor area. For upstairs, you may be able simply to double the ground floor area (if your house has two storeys, or treble it if you live in a three storey house). If the other floor area is a different size then calculate the upstairs area separately and add the figures together.

GEFA Includes

  • Perimeter wall thickness and external projections
  • Areas occupied by internal walls and partitions
  • Columns, piers, chimney breasts, stairwells, roof, lift-wells and the like
  • Integral garages
  • Conservatories.

GEFA Excludes

  • Attached garages, canopies and the like
  • Open vehicle parking areas, terraces and the like
  • Greenhouses, garden stores, external fuel stores and the like.


Semi-detached house measuring 12m by 5m; measurement taken to the external face of the house to the centre of the party wall:

  • Ground floor: 12 x 5 = 60 m²
  • Upper floor: 12 x 5 = 60 m²
  • GEFA = 120 m²

Measuring Your Flat

You need to find the gross internal floor area (GIFA) of your flat – that is the area measured to the internal face of the perimeter walls of the flat. You can measure either in feet or metres.

GIFA Includes

  • Areas occupied by internal walls and partitions
  • Columns, piers, chimney breasts and other internal projections
  • Porches and entrance halls within your flat
  • Internal stores, airing cupboards and the like
  • Service accommodation such as toilets, bathrooms and shower rooms
  • Conservatories

GIFA Excludes

  • Perimeter wall thicknesses and external projections
  • Common areas such as stairs, halls and landings
  • External open-sided balconies, covered ways and fire escapes
  • Canopies
  • Greenhouses, garden stores, fuel stores

Garages, Sheds, Fences and the like

If you have a separate garage or a garage built on the side of the house, an allowance can be added to the rebuilding cost by entering the number of car spaces in your garage or garages. An allowance will also be made for fences, gates, walls, patios, paths, drives, etc. If you have any special features, such as a swimming pool, then you will need to make allowances for them separately.