So says prominent Auckland devel' />

"Out of 1000 units I built, 100 of them leaked - what would I do differently now? Build everything in concrete."

So says prominent Auckland developer Rick Martin, acknowledging that three apartment projects by his Cornerstone Group on the North Shore had leak problems.

The 41-unit Oyster Cove at Gulf Harbour on the Whangaparaoa peninsula, the 40-unit complex at 282 Main Beach at Orewa, and an Albany apartment project all leaked to varying degrees, he says.

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

"I wouldn't put another sheet of that stuff up. There will never be a sheet of monolithic cladding put on anything we do. We're paranoid about it."

But he says Cornerstone is also building entirely different types of apartment blocks now, citing his new 117-unit, 30-level, $60 million Sentinel tower in Takapuna. These are vastly different from the low-rise, sprawling projects Cornerstone built on the North Shore.

Mr Martin, who built Orewa's controversial and distinctive high-rise Nautilus apartment tower, says the construction system has changed radically since the leaky building crisis emerged and people realised the scale of the problem.

Builders have implemented stringent testing regimes on structures as they rise from the ground, he says, citing Multiplex Constructions (NZ) which is building the Sentinel. Each window in the new tower is being tested immediately after it is installed to ensure seals are effective.

"There's no point in going back and finding problems with the windows when the lining's up."

Multiplex built a mockup apartment to demonstrate specifications and use of materials on each unit.

"Everyone working on that building knows exactly how the apartments go together."

He predicts the leaky building catastrophe will continue for a decade, affecting more than 60,000 houses.

Last week he gazed with awe at more than 100 units and houses in the Albany area - all built with monolithic cladding - as he considered the potential scale of the problem.

He is cynical about the regulatory regime, saying developers are forced to wait up to two years for consents, and it is almost impossible to get planning approval for multi-unit projects.

"The risk profile of developing buildings now is well out of kilter with the rewards. The Sentinel is the last apartment building we'll do. We got consent just at the right time because now it would be almost impossible."

He blames the Government for disbanding the Building Industry Authority, which he blames for the crisis and for failing to sound a warning. Asked what advice he would give developers, Mr Martin replied: "Don't build anything again."