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Floor area
Footprint : a key concept in town planning and architecture

The footprint is the projected surface area of a building on the ground, in other words the space it occupies on the plot. This concept is essential in the design of any architectural project, as it is used to assess the project's compatibility with local town planning rules, particularly those set out in the PLU (Local Town Planning Plan).

How is the footprint calculated ?

The footprint is the vertical projection of the volume of the building, including any overhangs (balconies, canopies, roof overhangs, covered terraces, etc.). Unlike floor area, it does not take account of upper levels or interior surfaces.

For example, a 100 m² single-storey house will often have the same footprint as its floor area, whereas a two-storey house with a floor area of 100 m² and 200 m² of living space will only have a footprint of 100 m².

Why is the footprint important ?

It allows you to :
  • comply with the rules for building on the plot (setbacks from boundaries, maximum density, non-buildable areas)
  • determine whether planning permission is required,
  • preserve green spaces and soil permeability,
  • manage environmental constraints, such as the floor area ratio (FAR) in some municipalities.

At ERHÉ architecture, we systematically include the calculation of the footprint right from the initial sketches, to ensure that the project is feasible in terms of the regulations.

An essential step in the administrative process

The footprint is a prerequisite for obtaining planning permission or a preliminary works declaration. It is also a criterion used to assess the environmental impact of a project and how well it fits into its context.