Workers at a home under renovation were given the scare of a lifetime when the house collapsed with them in it.

Calgary contractor Josh De Zwart, one of the men inside, said he felt the floor begin to shake and realized in terror the house was collapsing.

"It felt like an earthquake," he said.

After pulling himself and two other men out of the building at 2120 Cliff St. S.W., an unscathed De Zwart went straight home to hug his wife and kids.

"It was a harrowing experience," he said shortly after.

"I'm still shaken up about it."

The three men had been working on the third floor of the old home, estimated to be about 100 years old, when it suddenly toppled backwards about 2 p.m., landing at a 30-degree angle to the ground.

The neighbours on one side were thankful the house didn't crash into their home, although bricks smashed through their windows.

Nanny Malou Manzano was taking care of two children inside the neighbouring home when she heard the loud blast from next door and the shattering of windows.

"I was worried that house might fall and hit the whole house," she said, adding she quickly grabbed the boys and two dogs and ran outside to safety.

"When I saw the house I just panicked."

The boys' mom, Gabriela Ascencio, and dad Rob Myers rushed home to assess the damage and their kids.

"It's very frightening -- thank God that everyone is safe," said Ascencio.

Myers said the home had been gutted and only the side walls and the roof had remained.

"This isn't too surprising because they'd taken the whole front off as well as the back," he said.

Fire department spokesman Jeff Budai said the home will be demolished because it poses a safety risk.

The neighbours on either side have been forced to evacuate until it is torn down.

A city inspector has been called in to investigate what caused the structure to collapse.

TARINA.WHITE@SUNMEDIA.CA