Cover: the millimetres that decide how long a slab lasts
Concrete between the steel and the weather, measured in millimetres.
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In short: Cover short of the minimum, recorded more than once on Austral pours.
What cover is
The thickness of concrete between reinforcement and the outside face. It is what keeps moisture and air away from the steel.
What we recorded
Cover below the minimum on Austral slabs, on separate jobs, along with mesh sitting in contact with pipework where cover on that side was effectively nil.
What happens without it
Steel corrodes, and corroding steel expands. That expansion cracks the slab outward from the inside, which is not a repair anybody wants to price.
Why it is a pre-pour item
Because it is a dimension inside the concrete. After the pour there is no way to confirm it short of destructive testing.
The fix
Bar chairs and spacers, repositioning steel, moving a pipe. Minutes of work on the day before.
Written by our local inspection team from work carried out in Austral. Licensed building practitioners.
