The ‘Ground’ floor of a building is that on or nearest ground level.

The uppermost level of a building may sometimes be referred to as the ‘Penthouse’, ‘Roof’/’Rooftop’ or ‘Observation Deck’.

Where a building has entrances on two different floors, such as those built into a hill, the lower floor is known as ‘Lower Ground’ floor and the higher floor may be referred to either as the ‘Ground’ floor or ‘Upper-Ground’ floor.

The floor immediately below the ground floor/s is the ‘Basement’. There may be instances where it is referred to as ‘Lower Level’ (a non-preferred term).