Under L&I orders, the owner had hired a crew of two to take down part of the building and secure it. That's what they were doing when the floor collapsed, trapping a third man in the basement.
Rescuers responded around to the 100 block of Salford Street around 11:20 a.m. on a report that part of the home had collapsed and there were people inside.
A team of two contractors had been inside getting ready to make repairs on the home and they were rescued first.
"There was a contractor in the building preparing to actually do that work at which time the floors, which were severely water-damaged, gave way," said Karen Goss of L&I.
Witnesses said those contractors then alerted rescuers that a third man was trapped beneath the debris in the basement.
"Our understanding at this point is that that gentleman was not part of the construction crew and may have been in the building looking for scrap and that kind of thing," said Goss.
Specially-trained firefighters used airbags to lift away the debris around the trapped man. It took about an hour but finally he was freed from the rubble.
As the rescue had been underway, some residents on either side of the collapsed house were told to evacuate.
"They told us that we had to evacuate. We couldn't be in our house in case the house next door collapsed," said Marie Tyson.
The man who had been trapped was rushed to Penn Presbyterian Hospital for observation. His truck filled with scrap remained parked outside.
Within a few hours, another crew was back tearing down the roof.
L&I said the building had numerous code violations dating back to 2008.