How do I calculate the useable floor area?
If you have received an energy performance certificate (EPC) for your home or building, you can find the usable floor area on it under Description of the building and installations.
If you want to do the calculation yourself, follow this procedure:
Make the sum of the floor areas of all floors, including the outer walls. Partition walls with other heated flats only count for half. Walls between a flat and the common parts are also counted up to the axis of the wall.
Stairs and lifts are counted on each floor level.
A garage also counts, provided its walls are insulated and it is accessible from inside the house.
Basements and attics are not included, unless they are used as living space. For an attic, only count the floor area where the height of the roof is at least 1.5 m.