As residents continued moving in this week, the Newcastle Herald can reveal that a series of structural problems were uncovered at the almost completed apartment complex last month.

The twin-tower design, developed and built by Canberra's Bloc, offers what real estate agents describe as architecturally stylish apartments in the sky, some worth almost $2 million.

Situated on King Street in the heart of the city's emerging CBD, Newcastle West, the views from the landmark's two 19-storey towers are spectacular.

But when a hot water main burst on the ninth floor of the south tower of Verve Residences last month, the trouble was just beginning.

What the building walls had been hiding, a subcontractor working in the south tower uncovered.

The jarring note came when he found a structural blade wall, meant to be filled with concrete, with a large hollow pocket.

Read more: Burst water pipe causes damage to nine floors of Verve Residences building in Newcastle West

X-rays of the building walls revealed another large hollow section in a structural blade wall that separates two apartments several storeys higher and three other smaller hollow sections.

Photos and video obtained by the Newcastle Herald reveal workers holding their mobile phone cameras up to what is supposed to be a solid concrete wall and seeing straight through into the next apartment.

In some areas the only thing obstructing their view is exposed steel reinforcement bars.

Then, when workers stripped plasterboard from apartment walls after the water leak on the weekend of July 14, they found the rear of plasterboard wall linings covered in mould.

It is understood the photos were taken just days after the water leak.

The timing could not have been worse. Within days scores of removalist trucks would be pulling up outside the luxury apartment complex as residents began moving in.

Joint developer Warwick Miller confirmed that a German-made copper fitting on a hot water main from the building's services shaft broke, flooding the south tower's ninth floor and gushing water below.

The leak went undetected for about 10 hours on a weekend and water damaged 25 apartments. Another 20 apartments suffered minor water damage.

Joint developers Miller Property Corporation and Bloc delayed settlement on some apartments to allow for repairs.

Photos and videos show water cascading down staircases, water in electrical boards, wet carpets and apartment walls partially stripped of plasterboard.

In others, repair work has already started and sections of new plasterboard have been installed.

All of the copper plumbing fittings, like the one that failed, were replaced throughout the building.

When questioned about how fast the mould had grown, Bloc director and construction manager Drew Mathias said there had been no other water leaks in the building.

He said the areas where mould had been found were inside cavity walls where there was no ventilation.

"We engaged an independent expert hygienist," he said. "We met with the buyers and we told the buyers, 'Any part of your apartment that was exposed to water, we're not going to try and dry it out. We're ripping it out and we're giving you new.'

"Gyprock comes in 1200 [mm] sheets ... We take the entire bottom sheet out. We don't just cut a little bit out. We put in a new sheet, new skirting and new carpet.

"If the joinery got a bit wet, new kitchen. And we had an independent hygienist ticking off on everything."

It was not long after the water leak that the defects were uncovered in the blade columns, or party walls, that separate apartments.

Mr Mathias said the problems were detected in the walls as part of "quality assurance" work being carried out at the site, not because of the water damage.

He said workers were already X-raying the buildings' concrete structure as part of their "normal course of building" when a subcontractor found the first air pocket in a concrete blade wall below.

He said he did not know on which floors the larger air pockets were found, the Newcastle Herald understands one was located on the third floor in the southern tower.

"We're not hiding from the fact that there are defects when you build. What we feel very strongly about is that we find the defects, it's a normal part of business, and we close them out...," he said.

"At the end of the day the items you are talking about were fixed four days later, that's the machine."

Verve's structural engineer is Northrop, a Newcastle-owned engineering firm.

Northrop's chief executive Jamie Shelton said the repair work was completed last week and the building's structure meets the National Construction Code.

Mr Shelton said the exact cause of the wall failure was still under investigation, but it was "not a common occurrence".

He said once the first problem was found, a decision was made to test every wall in the building.

"We found two instances of significant structural defects," he said. "They were voids or boney concrete, there were two substantial issues and other minor ones."

The walls were repaired with high-strength concrete, also known as grout.

"It was an intense process as soon as we found these," he said. "What they have discovered here was a structural issue, it was an intensive process. We needed to ensure the integrity of every wall in the building."

Mr Shelton said this was an example of "good process" being followed to identify defects and deal with them properly.

He said there were no cracks or shifting detected.

"The walls now are absolutely of the quality we intended them to be," he said.

Bloc, a tier-two construction company, is Canberra's largest apartment builder having completed more than $2 billion worth of work.

Mr Mathias, who described Verve as "the Rolls Royce" of developments, said 12,600 cubic metres of concrete had been used on the job, an additional $2.5 million spent on "sending core piers to bedrock" and $2.5 million spent on changing the design to remove cheap aluminium cladding and replace it with a structural precast concrete facade.

"This is the best quality structure in Newcastle, it really is," he said.

"The builders who are out there building the buildings with the problems, they don't care, they just put it up and don't check it.

"We check and check again... That's life in construction, you are going to get the odd blade wall where the concrete hasn't settled properly... We found a couple more walls than we would have hoped, to be frank. But in the end we find them, then we fix them."

Mr Mathias said on a development the size of Verve, there would be between 50,000 and 100,000 defects detected and rectified.

"There are between 300 and 400 men on site at any given time, there is always going to be two or three not focused on what they are doing," he said. "Our job is to pick up on that and we close it out."

Verve was designed by Hill Thalis and CKDS architects. It comprises luxury one, two and three-bedroom balcony apartments that were initially priced from $309,500 up to $1.8 million.

Mr Miller, a veteran developer who plans to live at Verve, also built the nearby Castle Tavern (King Street Hotel) in the 1970s. He found the location for the development and had it designed, then Bloc joined as an equity partner in the project.

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