A structural engineer who was hired to figure out why a house in Mercer County suddenly collapsed in on itself says that it was an extremely rare occurrence.

Hamilton Township officials hired Bob Busch, a structural engineer with 40 years’ experience, to determine what caused the home on South Broad Street to fall apart. Tika Justice, 38, was killed and her two daughters were injured when the home collapsed Monday.

“It’s very unusual. It’s the first one like this I’ve ever seen. The house just sort of collapsed suddenly without warning, straight down,” he says.

Busch and his team theorize that years of water leaking into the basement of the home deteriorated the old form of concrete block that was used to build the home in 1920. The blocks found at the site were so weak that inspectors were able to break them apart with their hands.

“Some of the block below the first floor gave way, several first floor joists fell and rest of house went with it,” Busch says.

Busch says that what happened to the home is uncommon and very unlikely to happen again in New Jersey. He says that if a home’s basement is dry then everything should be fine. But if there is water in the basement, “take something like a screwdriver or nail and scrape it and it's soft and can easily be removed, maybe somebody should take a look at it."

The engineer says that he used a year’s worth of Google Earth pictures to determine if there are any signs that the home’s foundation was compromised.

His official conclusion: Failure of deteriorated concrete block due to long-term water penetration brought the house down.

Hamilton Township officials are collecting donations to help Justice’s daughters, who lost everything when the home collapsed.