Deck Danger

Now to our consumer watchdog report. Perhaps you remember that image, prom night gone wrong. The deck collapsing under so many young couples. But they were okay, but authorities say 40 million decks... See More

Now to our consumer watchdog report. Perhaps you remember that image, prom night gone wrong. The deck collapsing under so many young couples. But they were okay, but authorities say 40 million decks in america should get a second look. Elisabeth leamy with the story tonight. Reporter: It was prom night in indiana. Then suddenly chaos. Watch again, the deck goes down in just two seconds. These teens suffered bumps and bruises, but this inia woman broke her leg after her deck collapsed and other people have been killed. So what should you watch out for? First, experts say look for cracked and rotted wood. The people at this birthday party in redmond, washington, had no idea their deck was rotting, until it fell out from under them. Banging them up. Another warning sign is weak connections, like nails. Experts say make sure the deck is bolted instead, straight thugh to the skeleton of the house. There was a loud crack but there was nothing before that. We didn't hear any cracking. Reporter: Two people were in critical condition after this dramatic deck collapse in golden, colorado. Third, even if the deck is attached properly make sure the bolts aren't corroding. What happens when people ignore the warning signs? Abc news had this deck built with the number one flaw, those weak connections, just so we could demolish it and show you. One, two, three! Reporter: It's textbook like so many, our deck collapses against the building, adding a crushing hazard to the falling danger. That's why experts say if your deck is more than 15 years old, get it inspected immediately. Elisabeth leamy, abc news, washington.