The silver Corolla had a 30-year-old male driver at the wheel when it failed to negotiate a T-intersection at the end of Evans Street about 1.10pm on Tuesday.

Witnesses say the car showed no sign of braking before it smashed hard into the side of a Camry parked on Bank Street.

Both cars appeared to somersault into a three-storey unit block, including the ground floor unit where IT worker Philipp Mendelson was standing at his kitchen counter, looking out the window and eating a sandwich.

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"The car was coming very fast - it was like he was going as fast as he could. I just froze as soon as I noticed that - that it wasn't stopping," Mr Mendelson said.

"I registered what was going to happen. I was just trying to brace. I was hoping the wall wouldn't cave in, the car wouldn't come in.

"There was a huge impact. There was glass flying everywhere. I was like a deer in headlights."

The Corolla came to rest in a near-vertical position, partly inside Mr Mendelson's bedroom/home office, with the badly crumpled parked car embedded under it.

A neighbour, Kyle Smith, was among those who ran to try and help the injured driver. He said no one was able to reach the man, who was semi-conscious.

"Luckily no one was in the [parked] car or they'd be dead for sure," Mr Smith said.

Fire and Rescue NSW Inspector Chad Wallace said crews quickly hatched three separate rescue plans, coming at the wreck from in front and above (using a cherrypicker-style ladder) before taking out a window and some brickwork from an unoccupied second-storey unit to access the Corolla from behind.

"First arriving officers were confronted with a pretty rapidly changing scene, where the house was collapsing and the car was unstable," Insp Wallace said.

"In my 20 years, it's the most complicated [technical rescue] I've seen and definitely the most complicated we've seen here in Wollongong."

"We come to work to make a change and today those firefighters and ambulance officers without a doubt saved a life."

Crews freed the man after about 35 minutes and he was taken by ambulance to Wollongong Hospital, where he remained Tuesday evening in a stable condition.

NSW Ambulance's Inspector Troy Pan said the man was "super, super lucky" not to come away with more serious injuries.

"He had some abrasions to the face ... from the ultrasound it didn't look like he had done any internal damage," he said.

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Insp Wallace said the Corolla has been travelling at "breakneck speed". He said the collision had caused significant structural damage to the unit block and at least two units would be uninhabitable until repairs were carried out.

The 1970s-era complex is owned by a neighbouring resident, Cynthia Walker, who said she felt her own home shake on impact.

"Bricks and mortar can be replaced," she said. "It's very lucky no one was killed."

The destroyed Camry belonged to Koonawarra P-plater Kyle Anderson, who had parked on Evan Street the night before when he arrived at his partner's nearby unit.

"It was my grandfather's car - he left it to me in his will," Mr Anderson told the Mercury.

Police are now investigating the circumstances surrounding the crash and have called on any witnesses, or anyone with dashcam or other footage to come forward. Crime Stoppers: 1800 333 000.

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