Units and Terms

In Australia, the metric system is used for all construction dimensions. Dimensions on drawings are shown either as millimetres or as metres, although the suffixes for these (mm or m) are rarely shown. This doesn’t cause confusion, as it should be obvious which is meant – a bedroom shown as 3200 wide is not going to be 3200 metres!

Centimetres aren’t used in plans, with the exception that a tree may be shown on the site plan as ‘40 cm girth’. (It may be a requirement of the contract that some existing trees on the block are to be left untouched).

Dimensions in millimetres can be shown with or without a thousands separator, such as a comma or space. For example 3200, 3 200 or 3,200 can be used.

Metres are shown with a decimal point. They may show one, two or three decimal places. For example, the width of the building block may be shown on the site plan as 35.0, 35.00 or 35.000 (which all mean the same thing).

Occasionally other ways of showing sizes may be used. For example, windows in a brick building can be shown as brick courses high × bricks wide, such as 12 c × 4.5. This will make perfect sense to a bricklayer (and to you when you’re more familiar with the jargon used in the industry).

‘Length’, ‘width’ and ‘height’ are terms used as usual, but the term ‘depth’ can have a different meaning when used with building sizes. It can mean the distance from the front to the back of something. For example, a block of land that measures 35.0 m by 55.0 m would be described as 35.0 wide by 55.0 deep, although we would also say that the side boundary is 55.0 long.

Depth is also used to describe fitments such as cupboards and wardrobes – a 600 deep cupboard indicates that it is 600 mm from front to back.