A community group helping Christchurch homeowners get fair insurance settlements says it has found huge discrepancies in the city council's flood modelling.
The group, Empowered Christchurch, said because the council had set incorrect minimum floor levels for new homes, some were almost 50cm lower than they should be.
As a result, it said, new insurance rebuilds were significantly lower than the minimum required to protect against flooding.
Empowered Christchurch secretary Seamus O'Cromtha said some new builds would now have to be reassessed, as they were done with old council flood protection levels instead of ones that took effect in January 2011.
Christchurch City Council spokesman Peter Sparrow said only a small area of New Brighton was affected, and five properties that might be affected would be surveyed again.
Mr Sparrow said it had advised insurers through the Insurance Council to use updated information for any assessments or building work.