AUS Concrete Cover Specifications

Concrete Cover Specifications

Tolerances on concrete cover relative to the values shown on the drawings and specifications
In slabs and walls	+10, -0 mm
In beams and columns	+10, -0 mm
At ends of members	+25, -0 mm

Reinforcement shall be positioned in the formwork in accordance with the tolerances of 3.9(c) and 3.9(d) to provide the minimum concrete cover thickness as shown on the drawings and specifications.
Cover is measured from the outside of the stirrup hoop, spiral or tie to the exterior surface of the concrete.
Concrete cover thickness requirements will vary with different concrete strengths and specifications.
Where concrete is cast on or against ground and compacted in accordance with section 7, the minimum cover for a surface in contact with the ground shall be 75 mm or 50 mm if using a damp-proof membrane between the ground and the concrete to be cast.

Source
AS/NZS Standards documentation