This section applies for the purpose of section 117.
The height of a building is to be measured from ground level to the finished surface of the floor of the top storey of the building (ignoring any storey which is a roof-top machinery or plant area or consists exclusively of machinery or plant rooms).
When determining the number of storeys in a building—
any storey below ground level is to be disregarded;
any mezzanine floor is to be regarded as a storey if its internal floor area is at least half of the internal floor area of the largest storey in the building which is not below ground level.
In subsection (2) "ground level", in relation to a building, means—
the level of the surface of the ground immediately adjacent to the building, or
where the level of the surface of the ground on which the building is situated is not uniform, the level of the lowest part of the surface of the ground immediately adjacent to it.
For the purposes of subsection (3) a storey is "below ground level" if any part of the finished surface of the ceiling of the storey is below the level of the surface of the ground immediately adjacent to that part of the building.