When Troy Rivers was searching for an apartment to buy in Darwin four years ago, he found the perfect place, in a brand-new 12-storey building in the CBD.

Key points: The Catalyst building on Finniss Street is one of the nine apartment blocks caught up in a non-compliance building issue

The Catalyst building on Finniss Street is one of the nine apartment blocks caught up in a non-compliance building issue Homeowner Troy Rivers says he has been left devastated, partly due to the likely costs involved

Homeowner Troy Rivers says he has been left devastated, partly due to the likely costs involved The Infrastructure Department says the nine buildings affected are in Darwin and Palmerston

"I just wanted somewhere safe for [my wife], so she would feel secure," Mr Rivers said.

"I liked the look of it … and thought this would be a nice place to live."

But on Tuesday he received a letter from the Northern Territory Government, advising that his building, named Catalyst, on Finniss Street contained non-compliant structures requiring urgent assessment and rectification.

"We are pretty devastated because obviously it's going to cost us more money," he said.

Mr Rivers is one of about 200 property owners in nine separate residential apartment blocks caught up in a situation that centres on the work of a private, registered structural engineer.

Affected buildings in Darwin and Palmerston

The Department of Infrastructure, Planning and Logistics would not reveal which buildings were affected, apart from saying they were in Darwin and Palmerston.

The properties range in height from two to 12 storeys, and all have been built over the past five years.

Troy Rivers bought the Finniss St property in 2015, during the Inpex-fuelled construction boom. ( ABC News: Elias Clure )

"It's sensitive and we respect the wishes of the building owners not to release the locations of the buildings," said Mark Meldrum, the department's director of building control.

The structural problem in each of the buildings relates to the "transfer slabs", which are reinforced concrete slabs that distribute floor loads onto support posts and columns.

"The concern is that it might show signs of wear and tear and effectively the columns that hold up the slab may push through the slab and create a punching shear, (which is) the technical term," Mr Meldrum said.

The department said the nine buildings had not been deemed unsafe and residents could continue to live in them while the rectification process continued.

First complaint received in 2017

The department first received a complaint about the engineer's work in 2017, after someone on a building site raised concerns about the transfer slab being put in place.

Since then, the department has engaged a separate engineering company to audit the work of the structural engineer.

"Our structural engineers have done a desktop analysis only," Mr Meldrum said.

An artist's impression of the Finnis Street building. ( Source: DKJ )

"We've not had access to the buildings, and that's why we've asked the building owners to hire their own structural engineers and undertake that site inspection work to see if there are any signs of wear and tear."

Mr Meldrum said there was no indication that the structural integrity of any of the buildings had been compromised.

"Some of the buildings have been standing for five years, and at this stage and we've had no complaints about the buildings.

"So at this stage we believe the buildings are holding up well."

Residents have seven days to fix issues

Residents have been told they have seven working days to engage a structural engineer, who then has another seven days to devise a short-term solution to ensure the buildings meet Australian standards.

They then have a further 30 days to create a plan to fix the issue in the long term.

It is unclear how much it could cost to repair the issue in each building, but the owners will have to foot the bill.

"The responsibility for rectifying the non-compliances is with the building owner," Mr Meldrum said.

"It is a solvable problem."

The structural engineer at the centre of the saga is expected to be referred to the Building Practitioners Board "for an inquiry in alleged misconduct pertaining to a pattern of non-compliance with the National Construction Code," the department said.

Unit owner Troy Rivers said he is concerned the issue could have a detrimental effect on property prices.

"Darwin prices have gone down because Inpex is finished. And now with this information being given out, what's going to happen obviously is going to drive down prices even further," he said.