ENGINEERS BELIEVE COLLAPSE CAUSED BY TIMBER JOISTS FAILURE

Structural engineers and architects believe the most probable cause of the Berkeley balcony tragedy was a failure of the timber joists on which it rested. Such a failure was most likely to have occurred because of prolonged exposure to moisture which in turn would have caused a weakening and, ultimately, a rotting of the timber fibre.
The balcony was thus in a precarious condition and unable to support the weight of, it is believed, about a dozen people, some or all of whom were moving at the time of the collapse. Such a dynamic load, as opposed to a static or immobile weight, would have increased the stress on a structure that experts agree was already degraded.
Architect and premises safety expert Ron Bertone, of Palm Beach, Florida, estimated the size of the balcony, based on the size of the French doors leading out to it, as about 4ft by up to 10ft – or about 40sq ft. This would compute at a load-bearing capacity of some 24,000lb (or 1,088kg).