Thus if the location position or elevation of a

Thus, if the location (position or elevation) of
a concrete member is critical to the project, then
specifying appropriate tolerances in the project
documentation that are more stringent than those
allowed under AS 3600 is recommended.
Table ± Acceptable quality of formed surfaces (after AS 3610)
QUALITy OF SURFACE FINISh Class 1 Class ± Class 3 Class 4 Class 5
1 Blowholes refer photographs in AS 3610 for examples n/A n/A
± Form face deflection lesser of lesser of Greater of Greater of
2 mm or 3 mm or 3 mm or 3 mm or
span/360 span/270 span/270 span/270 n/A
Tolerance for straight elements with smooth surface, in millimetres
% of readings
95 100 90 100 80 100 70 100 70 100
3 Face step
within the element 1 2 2 3 3 5 5 8
at insitu construction joint 2 3 2 3 3 5 5 8 * *
4 Surface undulations **
l = 300 (a – b) ≤ 1 2 2 4 3 4 5 7 * *
l = 1500 (a – b) ≤ 2 4 3 6 5 7 8 10
5 Flatness
1.25 m grid 4 5 6 7 7 10 * * * *
at 5 m over 10 m 5 7 7 10 10 15 * * * *
(not applicable to precast concrete)
6 Out of plumb
height < 3 m 3 5 4 6 5 7 * * * *
3 < height < 8 m 6 8 8 10 10 12 * * * *
(not applicable to precast concrete)
notes
* limited by AS 3600
** a and b are respectively the maximum and minimum distances from the straightedge.
Figure 4: concrete frame may require tolerances
appropriate for the fitting of components such as
precast units.

Page 5 of 9
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tolerances for concrete surfaces
NATSPEC nATSPec nominates a flatness tolerance
for each of three classes of unformed surfaces, viz:
n
Class A Maximum deviation from a 3-m
straightedge is 3 mm.
n
Class B Maximum deviation from a 3-m
straightedge is 6 mm.
n
Class C Maximum deviation from a 600-mm
straightedge is 6 mm.
class A should not automatically be specified
for all floor applications. Achieving a maximum
deviation of 3-mm under a 3-m straightedge is
difficult and may require special construction
techniques at increased cost. referring to Table 1 ,
a reasonable tolerance for a conventional finish
would be a maximum deviation of 12 mm under a
3-m straightedge. With careful level control and
re-screeding where required, it may be possible to
achieve a maximum deviation of 8 mm under a 3-m
straightedge for the majority of a pavement area.
More-stringent tolerances should be specified only
if required for the application, eg a television studio
floor or operating theatre, both of which require
sensitive equipment to be moved across the floor. In
these cases class A may be the appropriate flatness
to specify, but consideration needs to be given
to achieving the specified tolerance on site. The
specification of a less stringent tolerance and use
of a self-levelling topping (after construction) may
be an option to achieve more-stringent tolerances,
particularly if suspended and/or post tensioned
floors are involved. Deflections after formwork
removal or stressing can easily exceed the ‘flatness’
tolerance specified. note that the waviness of the
floor may be more critical than having a class A
finish. Fewer ‘waves’ will effectively increase
the flatness and allow smoother movement of
equipment over the floor surface Figure ± .