The cost of repairing New Zealand's leaky buildings has blown out to $NZ11.5 billion ($9.36 billion) from the previous estimate of $3.6 billion ($2.93 billion).

Many NZ homes built in the 1990s have developed problems related to leaks due to faulty construction methods and materials.

Radio New Zealand has reported on a comprehensive repair plan to be hatched by the country's central and local governments, builders, developers and property owners in the wake of a report by accountancy firm PricewaterhouseCoopers containing the cost estimate.

The broadcaster says that where public money is used, people will be asked to sign a guarantee their money will be repaid from their estate when they die.