It's any investor's nightmare: A life's worth of savings locked up in an apartment you just cannot sell.

But after six years of negotiation and legal drama, that is exactly the problem faced by David Allen, who bought into Canberra's Elara Apartments in 2012.

"We were looking at a place for my daughter to stay and [it] was perfect, just across the road from the University of Canberra," he said.

That dream did not last long. Less than a month after buying the unit, problems started to mount.

Ivan Bulum is the director of 53 different companies, including B&T Constructions. ( ABC News )

"Water penetration was occurring within the unit, the balcony floor was leaking, [there were] floods in the car park," he said.

"We'd bought a lemon. How foolish were we?"

It turns out those problems were just the tip of the iceberg: Mr Allen would eventually find himself leading a group of owners chasing down a defects bill totalling $20 million.

But their story is just part of a web of problem development, failed legal action and apparently toothless regulation, all centred around Canberra-based B&T Constructions and its director Ivan Bulum.

Issues 'among the worst' expert had come across

Several cracks are visible on the facade of the Elara complex. ( ABC News: James Fettes )

The Elara Apartments were built in 2007, on a prime block of land in the north Canberra suburb of Bruce.

Its nearby lakes, schools and hospital were clear drawcards for one off-the-plan purchaser, who the ABC will call John.

"I thought, perfect investment … close to the pond, the business park area … I couldn't go past [it]," he said.

But John, who has a long history in the trades industry, started to notice red flags immediately.

Water damage and mould inside the Elara complex. ( Supplied )

"Down in the basement area, things were incomplete, not finished off," he said.

John reported the problems to the property manager and found the initial response promising.

"A lot of the earlier signs were that yes, we'll get onto this straight away, we'll come and fix this," he said.

"But things did seem to [drag] on for quite some time, a lot longer than they really should."

Eventually the owners took matters into their own hands, commissioning an expert report into the building's defects.

For starters, it found highly corrosive water leaking onto car paintwork through the basement.

"The only avenue to the unit owners at this stage has been to turn the landscape watering off and watch the plants die so that the carpark can at least dry out in between showers," the report read.

More urgently, the author warned of serious structural and fire safety risks.

In the event of a fire, he argued first-floor steel columns would fail in less than 30 minutes, rather the 90 minutes required by the Building Code.

The damaged balcony ceiling on a unit at Elara. ( ABC News: James Fettes )

The report found similar problems in the basement: "A fire engulfing these columns in our view runs a serious risk of collapsing the adjacent slab."

It also alleged some balconies were at risk of collapse — a claim the ACT Government took so seriously it ordered B&T Constructions to install propping to support the structure.

The company initially complied but removed some a few months later — without approval — citing their own report claiming the risk was exaggerated.

In the meantime other problems festered, according to waterproofing expert Ross Taylor.

"The scale and the complexity of the issues at Elara are amongst the worst that I've come across in my 40 years," Mr Taylor said.

"There's about 12 categories of issues … roofs, walls, bathroom leaking, balcony leaking, basement leaks and structural issues."

Owners would find themselves battling against rapidly moulding walls and cracked ceilings.

An initial estimate put the repair cost above $19 million, though the owners say that number continues to rise.

Waterproofing expert Ross Taylor examined defects at Elara. ( ABC News: James Fettes )

Scuttled legal action

The Elara owners' corporation attempted to claim that money through the courts, accusing Mr Bulum's B&T Constructions of multiple breaches of the Buildings Code and other laws.

The litigation sat largely dormant until the owners moved to restart proceedings in mid-2017, relying on a eight expert reports to bolster their case.

Damage to a wall at the Elara complex in Canberra's north. ( ABC News: James Fettes )

But it was all for nothing: The very next day, B&T Constructions moved into voluntary administration, meaning the case was scuttled.

"It [was] like someone just stuck a big pin into a balloon … and all of a sudden you've just got this piece of rubber on the ground," Mr Allen said.

"We thought we were getting close on a number of occasions and to have them just go away was really disheartening."

John agreed: "I was burnt out, I didn't have any more in me to fight it," he said.

To make matters worse, administrators told prospective creditors that any money raised from B&T's liquidation would likely go back to its director, Ivan Bulum, through an associated company that was owed a secured debt of $1.7 million.

Insurance is now the only recourse left to Elara's owners and would only cover about half the alleged rectification bill.

The decade-long saga has taken a sledgehammer to the reputation of the building: Mr Allen has seen the value of his unit drop $40,000 to $50,000 in five years.

"I should be retired now and living the dream. But this is the dream, which is really a nightmare," he said.

B&T's other defective properties

Elara was built in 2007. ( ABC News )

Elara is just one defect-riddled complex connected with B&T Constructions or Mr Bulum.

The Empire Apartments in Forrest, described in advertising as "the epitome of luxury, prestige and convenience", featured 37 breaches of the Building Code and other legislation.

The builder deviated from approved plans on multiple occasions; swapping out high-quality stone and aluminium cladding with cheaper cement board and rendered paint finish, and not providing glass balustrades as promised for the building's penthouse apartments.

Cracks beneath a window at the Elara complex in Canberra's north. ( ABC News: James Fettes )

The company appealed against three breaches in the territory's highest court — and lost.

"The building as constructed is of an inferior standard or quality to that for which [B&T Constructions] had lawful approval," the majority of the court found in a 2-1 decision.

Another block in the Weston Creek suburb of Holder was subject to an emergency government order targeting a range of defects, including a broken sewerage pipe.

"A sewerage leak … was detected with significant effluent discharge seeping through the block wall within the garage adjacent to the main panel lift entry door," a report cited in the government order read.

The total repair bill was estimated to be as high as $300,000.

In explaining his decision to issue the order, the Deputy Construction Occupations Registrar said the work would mitigate risks to health, safety and property.

"I am satisfied that the premises was built in such a way as to pose a risk to building occupants … [and] that rectification work needs to be undertaken immediately," he said.

A game of cat and mouse

Elara is not the only Bulum-connected complex with construction issues. ( ABC News: James Fettes )

For almost three decades government regulators have been trying to hold Mr Bulum accountable.

In the early-to-mid-90s, the ACT Government tried three separate times to force one of Mr Bulum's oldest companies — I&M Holdings — into liquidation over unpaid debts totalling more than $150,000.

The Australian Taxation Office (ATO) tried to do the same with another Bulum company, B&T Homes, over $1.4 million in unpaid debt in 2004.

The ATO's territory counterpart tried to liquidate a third Bulum company, 4/49M Pty Ltd, over almost $35,000 in outstanding rates and interest.

Each time, the action was either withdrawn or dismissed.

Much of the Government's efforts against Mr Bulum and his associates have involved the Construction Occupations Registrar, which handles ACT licensing.

Elara residents have seen property prices plunge as defects became apparent. ( ABC News: James Fettes )

With the issues at Empire and Elara seemingly going nowhere, in 2014 the Registrar asked the ACT Civil and Administrative Tribunal (ACAT) to strip B&T Constructions, Mr Bulum and an associate of their building licences for five years.

ACAT did not cancel any, but did fine B&T Constructions $10,000 and force it to fix problems at Empire or face suspension.

The company did not comply, so its licence was suspended in April 2016.

The Government also tried to reject a building licence application from another Bulum company, Minotaur Constructions, even going so far as to draft and pass legislation allowing it to do so "to protect the public".

But the company had that decision set aside by arguing the legislation could not be applied retrospectively.

A life in construction

Mr Bulum was born in Croatia in 1945.

He appeared as a witness at the Trade Union Royal Commission in 2015, telling the hearing he had more than 50 years of experience building in Canberra.

Ivan Bulum gave evidence at the Trade Union Royal Commission in 2015. ( ABC News )

On Wednesday, Mr Bulum directly controls 53 different companies, some with virtually identical names like 19/29 Pty Ltd and 19/29BT Pty Ltd.

Since the demise of B&T Constructions, a new corporate identity — The Bulum Group — has appeared to take the lead, ushering in a major redevelopment of Braddon's Lonsdale Street.

That company is responsible for at least four projects on the formerly industrial street.

Neither The Bulum Group nor any other Bulum company holds a current ACT building licence — instead Mr Bulum has turned from builder to developer, contracting out construction to Canberra-based companies.

The ABC is not alleging the presence of defects in any of these newer properties.

'No-one takes responsibility'

The saga at Elara has raised questions about how the Government handles problem building work.

With B&T Constructions wound up, there appears to be no way for the owners to pursue funds from Mr Bulum and his companies, even as they continue to develop major projects across the city.

The Bulum Group is not captured under so-called anti-phoenixing legislation — which seeks to stop builders shifting companies — because it does not cover developers who do not physically construct their own projects.

Beyond that, Mr Allen said lack of action from the Government worsened the experience.

"It's been really difficult to get someone to say 'I'll stand up, I'll take responsibility and I'll do something for you'," he said.

"As long as you accept poor performance, you'll get poor performance."

Mr Bulum did not respond to a series of questions and instead referred the ABC to the liquidators of B&T Constructions.