These cracks became visible in the slab around the centre of the garage doors after the first rains for the year (the destructive thunderstorm that struck Perth).
The visibility is accentuated by the presence of rain water laying on the surface of the cement and soaking in to the fissures.
It's a bit worrying to me as I am concerned that I am about to experience major structural subsidence problems.
Monday 8.30 29/3/2010 - an engineer from Screw Pile Australia met me out on site and had a look.
Fortunately, he says he is sure I have no problem - what I am seeing is some minor crazing of the cement due to forces in the concrete beam stretching the upper surface.
He checked my structural engineering diagrams to make sure that there is reinforcement bar in the upper layer of the cement to counter this force and was satisfied that everything had been correctly engineered.
The screw piles themselves are not moving.