The Institute of Surveyors has criticised the way Christchurch homes have been measured to establish if they need foundation repairs.
Some homeowners have complained the Earthquake Commission ruled their houses were not sufficiently out of kilter to warrant repairs. The institute has just published a report examining the Ministry of Building, Innovation and Employment's guidelines for checking if floors are tilted.
The report is highly critical of some practices and said it is disturbing to find some assessments are being done incorrectly by people who lack surveying skills.
It recommends qualified surveyors be used when measurements are contentious or when legal action appears likely.
The report's lead author, John Hannah, said homeowners struggled to trust assessments carried out by people who weren't qualified.
"I would be reluctant to have some inadequately trained work on my place. I guess it's a bit like building a house, I would be reluctant to employ someone who has inadequately trained as a builder," he said.
A professional land surveyor, Adrian Cowie, said the consequences of not using professionals were dire.
"Houses are getting repaired incorrectly and they're being left with major structural damage that isn't being repaired because EQC hasn't tested levels properly," he said.
Adrian Cowie said EQC's current measurement practices will only mean a bigger mess to clean up if there is another earthquake.
EQC has set a floor level threshold of 50 millimetres, meaning if a floor is more uneven than that because foundations have moved, it must be fixed.
Burwood resident Selwyn Stafford said EQC assessors found a 40 millimetre bend in the floor of his house.
But he wasn't convinced, so he hired an independent surveyor who found the bend to be 85 millimetres.
He said it was time EQC started using professionals.
"They're big decisions and a lot of money can be spent and wasted if there's inadequate assessment of your foundation float," he said.
"They should be well qualified and experienced. How else can they expect to stand in court as an expert witness," he said.
But EQC's Engineering Advisor, Tim Day, said he hasn't seen any evidence of the Commission getting a floor assessment wrong.
"As far as I'm aware we haven't had any negative feedback on the floor level surveys that we've undertaken," he said.
He said the Commission has only just received the report and wanted to meet with the institute and discuss the recommendations.
He said professional surveyors were already being brought in where cases were contentious or may involve legal action
But Adrian Cowie said he has seen EQC personnel doing the testing and doing it wrong.
The Ministry of Building, Innovation and Employment would not comment on the Institute of Surveyors' report.