Christchurch City Council is certain a mistake calculating flood levels is confined to five homes.
The South Brighton houses have all been rebuilt following earthquake damage.
But due to an error in calculating the threat posed by sea level rise, they have not been built high enough to avoid future flooding.
Empowered Christchurch said last week because the council had set incorrect minimum floor levels for new homes, some were almost 50cm lower than they should be.
As a result, new insurance rebuilds were significantly lower than the minimum required to protect against flooding, it said.
Since the mistake was brought to he council's attention, it has been attempting to find out how many homes are affected.
Local ward councillor David East said he received a staff briefing this morning confirming the problem was confined to the five houses already identified.
"The information that has been given to me today would indicate there is no absolute immediate danger of flooding of these properties, but certainly over a longer period there are some implications that need to be addressed."
It was unclear what sort of help the homeowners were eligible for, he said.