This number underpins the calculation of the rebuilding cost of UK homes which drives rebuilding insurance premiums for home owners.

BCIS have advised that the easiest way for homeowners to measure the gross external floor area of their property is to measure the length and width of the house and multiply these together. For those measuring inside, the thickness of the walls should be added and any integral garage would also need to be included in this calculation.

To calculate an upstairs floor area, it may be possible to simply double the ground floor area but if it is a different size, calculate the upstairs area separately and add the figures together.

BCIS highlighted that for three storey houses, only 70% of the floor area of the third storey would need to be included. A third storey of a house does not mean the attic in a two storey house, unless the roof space has been converted into a third storey.