An Auckland concrete expert has warned that there could still be cracks hidden in concrete foundations of tens of thousands of Christchurch homes – even nine years on from the Canterbury earthquakes.
Bevan Craig, managing director of Underfoot Services, shared that they inspect homes without visible cracks but would eventually find fractures once the foundations were checked – adding that the worse damage is often buried out of sight.
He explained that poor materials for the foundations are likely to blame as some of them just shatter and slide.
“You can imagine in an earthquake, all these smooth river stones get shaken up. The fines, the sand, also wash away. The slab on top can’t follow and so voids are created,” Craig told Stuff.co.nz.
David Townshend, a member of the EQC Claimant Reference Group, said the problems are way bigger than anyone wants to admit.
“Look at the latest payments the Crown is having to dish out – about $1 billion to cover re-repairs and on-solds. Those are mostly about foundation issues coming to light,” he told Stuff.co.nz.
“EQC thought it could patch properties – keeping them under its $100,000 insurance cap – by ‘jacking and packing’ foundation piles or levering up the corners of a slab … EQC’s assessors did not make a habit of lifting carpets or crawling about under houses. Foundations were presumed sound unless the damage was too obvious to ignore.”
“Logically, the proper way to assess earthquake damage is ground up. If the land has moved, drains and foundations ought to be checked first. They are the expensive problem. There is not much point worrying about the house above if the damage below is not addressed,” Townshend concluded.