When excited first home buyer Jae Jun Kim went to inspect the one-bedroom apartment he’d bought off the plan in Sydney’s CBD, he discovered something vital was missing: the bedroom.

Where the wall to the bedroom and the much-lauded feature decorative glass sliding screen door should have been was … nothing.

Instead, the slick one-bedroom apartment in the new 15-storey building The Castlereagh that Kim had paid $560,000 for in October 2012 was actually a studio. He was distraught.

“I went to the inspection and it was an absolute shock,” says Kim, 27, a senior design consultant with Deloitte Australia. “I couldn’t believe my eyes. It was nothing like the vision I had been sold.

“My first question, of course, was, ‘What happened to the bedroom?'”

The answer from developer Lenland​ Property Development wasn’t at all helpful. Their lawyers wrote to Kim to say they’d had to remove the bedroom wall and sliding doors that created the room. They noted that was a “substantial and detrimental” change to the property but passed the blame to Sydney City Council.

Planning officials, they said, had insisted they remove the wall and sliding doors separating the bedroom “to comply with solar access requirement (sic).”

But according to Building Code of Australia design rules, the council had no choice; the unit in the block, on the corner of Bathurst Street and Castlereagh Street, should never ever have been classified, marketed and sold, as a one-bedroom apartment.

Firstly, the bedroom was set against a blank, windowless wall, offering no natural ventilation. A glass sliding door to the rest of the unit wasn’t an acceptable substitute.

And secondly, the apartment was too small, at 42.3 square metres internally. At the time the development application was assessed, a council spokesperson said it was required to comply with the NSW Residential Flat Design Code which required one-bedroom apartments to have a minimum internal area of 50 square metres, not including balcony areas.

Lenland’s lawyers then gave Kim seven days to either accept the studio – with the sweetener of a free timber floor in the area where the bedroom should have been instead of the carpet – or they would rescind the contract.

Lenland managing director Benny Deng messaged Domain to say he couldn’t return calls and passed us on to project manager Richard Abbott of RJ Projects.

He said, “There was a discrepancy between the architectural drawings that we submitted to council and the detail in the sales documents for that particular unit. I’m not sure of the detail but we were required to remove the wall. It was an oversight.”

He said the buyer had been offered an opportunity to rescind the contract, so he wouldn’t have to settle on the apartment, and there had been an offer to change the floor covering in the area that would have been the bedroom.

“There may be other things we can offer, compensation, depending on the individual circumstances.”

The website for The Castlereagh​ also went offline on Wednesday after Fairfax Media placed calls, and images of the tower appear to have been taken off the website of its builders Hamilton Marino.

In the meantime, Kim remains devastated by his discovery. “I was very heavily dependent on buying this one-bedroom apartment,” says Kim, who’s now consulted a lawyer about what he can do. “I’d been planning to live there and I’d been waiting for three years for this to be finished as it went over time too. Now this is so distressing.

“How can developers get away with this kind of stuff when people buy off the plan? They sold it as a one-bedroom apartment and how come it’s only now that they’re telling me it’s turned into a studio? What chance does the ordinary buyer stand when developers act like this, and the authorities let them?

“If I’d wanted a studio, I would have bought one – and for a lot less money! Now prices have gone up a lot in the last three years while I’ve been waiting.”

In addition, from Kim’s inspection, he says the actual finishes bear little relation to the “rich and elegant materials” that were advertised. “As a designer, I’d been drawn to the design of the apartments, but that’s extremely disappointing too,” he says.