CHICAGO (CBS) – A deck collapse in Miami that injured dozens of people, may have some in Chicago asking if their deck is safe.

One expert tells CBS 2’s Chris Martinez that some are in worse shape than you think.

“There are things going on that we can’t see,” said structural engineer Daniel Roig

Hidden defects, like rotting wood, are the reasons why.

Roig says sudden changes of weight or movement can bring a deck down

“Like standing up all at the same time or having something like a dance party,” Roig said.

Among to worst deck disasters happened 10 years ago in Lincoln Park when the second and third floors of a deck collapsed, killing 13 and injuring many more.

That disaster led to changes in Chicago’s building codes, and Roig was part of the team that rewrote it.

“We changed a lot of details,” he said. “If you look in the code now you’ll see there’s a whole section specifically on how to build decks.”

Still, he said, codes alone won’t keep you safe when you step out on a deck.

“You’re hoping that the owner did his due diligence to keep everything proper,” Roig said.

He advises that homeowners should have their decks inspected if they have concerns, and especially if there is any rotting wood.

Residents can request an inspection from the city by calling 311.

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