(CBS) — An Evanston porch collapse injured four Monday night during a holiday cookout.

CBS 2’s Derrick Blakley found, it’s sometimes tough even for experts to spot a hazard.

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The collapse, happened it seconds, falling wooden boards and beams followed by chaos.

“No warning at all,” said Deliah Walker. “We felt like a little movement and everyone froze and then boom, that was it.”

Walker was one of four injured in the pile of debris and bodies. What happened, experts say, was likely caused not by too much weight, but rather by too little diligence in construction or maintenance.

“My understanding is there were 10 or 12 people, unless they were big partyers, jumping up and down, I just don’t see loading causing this kind of collapse,” said structural engineer Homa Ghaemi. “It’s the connection failure.”

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The connection, that is, between the porch and the building itself, but often, a tenant can’t see the potential danger.

“Sometimes, you see shifting of some elements like the joist, the rims, the ledger, something is loose, but a lot of times you just can’t tell. Visibly it’s not possible.”

Chicago dramatically toughened porch regulations after a 2003 Lincoln Park collapse took 13 lives. Still, most renters must depend on landlords to make sure their porches are safe.

“Which is why I think it falls to the local municipalities to have a very strong inspection and enforcement mechanism,” said construction attorney Jeffrey Youngerman.

Jeffrey Youngerman is the husband of a CBS 2 producer.

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An Evanston official told CBS 2 exterior inspections of buildings in that suburb are conducted every three to five years. Authorities wouldn’t say the last time that building was inspected or whether it had a history of complaints and our calls to the landlord of record were not returned.