Schedule 4 to regulation 7 specifies those methods of measurement that are necessary for the regulations themselves. In the Technical Handbooks certain additional measurements are also used, and references to additional methods of measurement specific to particular sections are included in the introductions to those sections.
Measurement of area shall be taken to the innermost surfaces of enclosing walls or, on any side where there is no enclosing wall, to the outermost edge of the floor on that side.
A room excludes any built-in fixture extending from the floor to the ceiling.
In the case of a dwelling, a room excludes any part where the height is less than 1.5m.
Height and depth
The height of:
a building shall be taken to be the height from the surface of the ground to the underside of the ceiling of the topmost storey or, if the topmost storey has no ceiling, one-half of the height of the roof above its lowest part, and
a storey above the ground or the depth of a storey below the ground shall be taken to be the vertical height or depth as the case may be from the ground to the upper surface of the floor of the storey, and the expressions “a storey at a height” and “a storey at a depth” shall be construed accordingly.
In the measurement of height or depth from ground which is not level the height or depth shall be taken to be the mean height or depth, except that:
for the purpose of types 1, 2, 3, 4, 5, 18 or 19 of schedule 3, and
for any other purpose where the difference in level is more than 2.5m, the height or depth shall be taken to be the greatest height or depth.
Except where the context otherwise requires, measurements shall be horizontal and vertical.