(1) Where the height of a building or occupancy-unit is given in storeys, as set out in this Chapter, the number of storeys shall be regarded as those contained between the floor nearest the finished ground-level, at the point considered, and the roof of such building or the top of such occupancy-unit.

(2) A mezzanine floor having an aggregate floor area exceeding 20 per centum of the floor area of the storey in which it is located shall be regarded as a separate storey.

(3) Where the height of a building or an occupancy-unit is given in metres, as set out in this Chapter, the height shall be regarded as the vertical distance between the unfinished ground-level, at the point considered of such building or occupancy-unit, and the underside of a flat-roof construction or a point half-way up the roof-pitch in a sloping-roof construction.

(4) Where structures which are erected on the roof of a building or an occupancy-unit contain habitable rooms, used as part of the occupancy of such building or occupancy-unit, the height shall be the vertical distance between the ground-level, at the point considered adjoining such building or occupancy-unit, and the underside of the ceilings of such rooms.