Leaky building settlements cost Hamilton City Council $590,000 last year and early indications show the 2012/13 bill could be much larger.
Councillors were warned at a confidential meeting earlier this year to brace themselves for a further blowout of next year's modest $250,000 budget.
The information, released to the Herald under the Official Information Act, revealed that settling its four claims last year cost an average of $147,500 a home.
The total cost for 2011/12 was more than double the $236,000 the council had budgeted for.
As well as the 15 active claims the council is processing, the Weathertight Homes Resolution Service showed there were 24 active claims for the city, although some of these might not meet the criteria.