OUTDATED SNOW loading requirements in Polish building codes have emerged as the key contributing factor to last month's collapse of the flat roof of an exhibition hall in Katowice.
More than 60 people died in the tragedy.
Around 500 visitors were attending a racing pigeon exhibition in the Katowice Trade Hall when the collapse occurred.
The even ear old, 100,000m 2 building was experiencing the worst winter by far since it opened. It is reported to have had more than 500mm of compacted snow and ice on its roof at the moment of collapse.
The roof of the steel framed building is reported to have been designed to take up to 800mm of normal snow, then in line with the local codes.
But a recent analysis of Polish snowfall records over the last 50 years has found that in some areas the design snow loading should be up to 70% higher.
Recent prolonged sub-zero temperatures could also have increased the chances overloading from snow and ice.
'Under those conditions heat leaking through the roof can melt the lower layers of snow, which refreeze as ice when the heating is off, ' said UK Steel Construction Institute director Graham Owen. 'Over time the density of the 'snow' will approach that of water.' Owen added: 'The roof trusses were more than 10m above floor level. At that height any excessive de'ection would have been very hard to spot.' Dave Parker