Australian Standard

Levels of contours and specific points should be indicated by the appropriate recommended symbols. As per Australian Standard 1100.301, the convention for expression of levels states that they should be expressed in metres to the nearest multiples of 5mm (0.005m) to three decimal places. Where the level of an existing feature is to be varied, the existing level should be placed directly above the box containing the required level as shown in the example below.

the symbol for levels, showing the existing level and the required level.

This symbol should be drawn adjacent to the area name or code. If the levels may be confused with other numbers or symbols on the drawing, such as room numbers or dimensions, you should use the prefix RL (reduced level) or FFL (finished floor level) as per the following example.

the symbol for levels, showing the use of the prefix RL to indicate reduced level.

Showing levels on a drawing or plan

There are three methods you can use to indicate levels on plan views, as follows.

Job datum level

The job datum level is indicated by its symbol, followed by the numbers for that level. The position of the job datum should be clearly marked on site plans, along with its assumed level as per the example below (the first symbols is for the job datum).

the symbol for job datum level and the numbers for the level.

Spot levels

Spot levels are used to indicate the required or existing level for a specific point or limited area. On a drawing or plan, it will be shown by a symbol placed at the exact spot where the level applies, followed by the numbers for the proposed or existing level. The examples below show three different ways of showing this.

three methods of showing spot levels.

Contour lines

To indicate the slope and shape of the ground surface, you'll use contour lines. These lines are drawn so that they pass through all points on the site that have the same reduced levels. The method for showing this is to place the RL at the end of each line at the site boundary, or at intermediate points in or on the line if it's a large site. On a drawing or plan it will look something like the example below (remembering to follow the conventions for line thicknesses).

an example of a contour line showing the RL.

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