Floor Areas, Perimeters and Schedules

≈ 36 min

Floor Areas, Perimeters and Schedules

A building plan carries quantities as well as geometry, and CAPS requires you to calculate them from your own drawing.

Floor area is normally quoted as the internal area — the usable space, measured inside the walls. A room 4 200 × 3 600 mm internally has an area of 4.2 × 3.6 = 15.12 m². Note the unit change: dimensions are in millimetres, areas in square metres, so convert before multiplying rather than after.

Perimeter is the distance round the room, used for skirting and cornice quantities: 2 × (4.2 + 3.6) = 15.6 m. Openings are deducted for skirting, because no skirting crosses a doorway.

Schedules tabulate repeated components — a door schedule and a window schedule listing each unit's mark, size, material and quantity. The plan then carries only the mark (D1, W3), keeping the drawing readable.

Worked example. Quoting the external area instead of the internal one overstates a 15.12 m² room by roughly two square metres on a 230 mm wall — enough to mis-order flooring and to misstate the area on a municipal submission.

Core checkpoint: State which area you are quoting. Internal and external areas are both meaningful, and they are not the same number.

A room measures 4 200 mm × 3 600 mm internally. What is its floor area in square metres?

What is the perimeter, in metres, of a room measuring 4.2 m × 3.6 m internally?

Why should millimetre dimensions be converted to metres before multiplying for an area?

Multiplying first gives mm², which must be divided by 1 000 000 — an easy step to get wrong.

Because millimetres cannot be multiplied.

Because the answer would be too large to write down.

It makes no difference which order is used.

What is the purpose of a door or window schedule?

To tabulate each unit's mark, size, material and quantity, so the plan need only carry the mark.

To record the order in which doors are installed.

To list the tools needed for installation.

To show the doors' opening directions.