Photo prior to collapse courtesy Google Streetview.
The Inquirer has details on what caused Monday’s Cobbs Creek rowhouse collapse. L&I told Jason Grant that the homes at 6015 and 6017 Spruce collapsed because the foundation beneath their shared party wall had been deteriorating over decades.
The culprit, according to L&I Commissioner Carlton Williams, was a foundation that had been made of rubble stone and mortar. Modern construction relies on foundations made of continuous slabs of concrete, but older construction commonly used the same mixture found on Spruce Street.
An ominous warning about how easily deteriorated foundations can lead to structural problems:
Generally, Williams said, even one loose or missing stone in a rubble wall – which can get dislodged as mortar surrounding it gradually deteriorates to dust – may lead to a collapse.
If reading that gave you heart palpitations, Williams has a suggestion:
Williams noted Tuesday that many homes in the Northeastern United States were built with rubble stone and mortar foundations. He and L&I Emergency Services Director Scott Mulderig said anyone with turn-of-the-century or early-1900s homes should check basements at least yearly for loose or missing rubble stone; a dusty or sandlike buildup of deteriorated mortar; or water that could signal a compromised foundation or wall.
Most importantly, no one was hurt in Monday’s collapse. Grant talked to one of the homeowners who was at work when she got the news and raced home to find her two Scottish deerhounds – both safe.
A self-described pragmatist, she said, “Good things happen, bad things happen – you just hope the good ones outweigh the bad ones, but sometimes they don’t.”
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