EXCLUSIVE: One of New Zealand's most controversial apartment blocks, the $65 million Nautilus apartment tower in Orewa, is the latest victim of leaky-building syndrome.

Leak specialist Prendos has been called in to investigate problems at the 12-level tower, which dominates the beachside town.

One source said the repair bill was expected to reach $19 million, which would make it New Zealand's most expensive leaky building.

The Nautilus tower dominates otherwise low-rise Orewa's skyline, and was widely opposed by residents when developer Rick Martin sought planning permission for it.

This week, Mr Martin acknowledged the building had problems, and blamed international builder Brookfield Multiplex.

Maintenance had not been done properly, Mr Martin claimed, and if the blame lay anywhere it was not with his Cornerstone Group.

John Pringle, who owns an apartment on level eight of the tower and heads the Nautilus owners' committee, said all inquiries about problems were being handled by the body corporate secretary, Centurion Management.

Asked about leaks, Mr Pringle would only say: "We haven't had any report back yet."

Philip O'Sullivan, of Prendos, yesterday said his firm had been engaged to complete a detailed analysis.

Prendos has specialised in investigating complicated leaky-building problems, believed to have affected between 30,000 and 80,000 New Zealand properties, including many multi-unit blocks built within the past nine years.

The 152-unit Nautilus at 9-13 Tamariki Ave was built six years ago and units sold from about $250,000 each.

It is not yet known how many units are affected.

One source who knew about the tower's problem said Nautilus repairs could make that block the subject of the country's largest weathertightness dispute.

"The building has had a failure of the alucobond cladding, and all cladding, substrates and deck finishings have to be ripped off and replaced," he said

Work on the project had started.

"The cost is $133,000 per unit, which is approximately $18 million to $19 million."

Dan Ashby, managing director of Brookfield Multiplex Construction (NZ), which built the tower, said that in November, he had offered to meet those involved but had heard nothing since.

Around that time, he was sent extracts from a Prendos report indicating "systemic and global failures" at the tower and maintenance and design detail problems.

These allegations were sweeping generalisations, he said, and not helpful.

Mr Ashby is understood to have written to Mr Martin, challenging the Prendos report and saying Brookfield was not responsible for the tower's design.

Mr Ashby said he was willing to discuss the issue, but the builder's job had finished years ago, and his company had received no notification of any claim against it.

A Rodney District Council spokesman said he knew investigations had been done, but the council was not involved because no application had been made for repairs or recladding and no litigation issues had been raised.

Cornerstone, Multiplex Construction, Walker Architects and Rodney District Council were all involved when the building went up, he said.

Many Nautilus units are for sale or rent. Some are advertised on a website that is offering some nights free.

Mr Martin said three years ago that out of more than 1000 units he had built, only about 100 leaked.

Claddings were a major contributor to the problem and he had banned the use of all fibre-cement plaster-coated monolithic sheet cladding products from all projects.

NZ's most expensive leaky buildings:
$11 million won by owners of the 153-unit Sacramento complex in Botany Downs.

$15 million sought by owners of Farnham Terrace, a 41-unit Parnell block.

$18-19 million? estimated cost to fix the Nautilus tower in Orewa.