1)   Footprint = measured around the outside of the building and including any part of the building - habitable or not - which is both covered & enclosed (a roofed terrace is excluded but a conservatory would be included.

2)   Habitable area = measured around inside finished surface of walls (i.e. insulation and plasterboard are outside the line, this is done for all habitable areas on all floors, but you can delete parts of a room with a ceiling height of less than 1.8m and the space beneath a stairwell.