How to avoid roofs collapsing under the weight of snow and ice
The last major snow-related roof collapse in the UK happened at a Tesco Superstore in Scunthorpe, back in 2010. On a Friday afternoon in late December, shoppers were stocking up for the weekend when 320 square feet of the canopy roof buckled under the snow’s weight and crashed to the floor.
Amazingly, no one was in that part of the store, so nobody was injured. But if anyone had been there they would have been crushed. It was lucky the collapse didn’t happen a day later, on Saturday, when many more people would have been in the store.
Recently, when the so-called “Beast from the East” hit the UK, we saw extreme weather conditions, but I haven’t heard of any major roof collapses. There may have been minor collapses, but no deaths or major injuries have been reported.
When we’re planning buildings we know we need to allow for snow. Roofs need to be able to cope with a heavy load, and structural engineers will always take this into account. Luckily the building regulations in this country ensure that roof collapse due to snow is very rare.
When it does happen, it highlights that the people in our sector have a great deal of responsibility. The work we do saves lives by preventing the serious injury and death that could occur in a collapse situation.
Collapses are mercifully rare across Europe due to good building regulations and maintenance standards. Where collapses do happen, there are usually other factors at play.
One of the worst cases in recent years was in 2006, when the roof of one of the buildings at the Katowice International Fair in Poland collapsed. Sixty-five people were killed and more than 170 injured.
Sadly, this tragedy could have been avoided, as the roof had buckled under the weight of snow back in 2000, but only emergency repairs were made. The design of the building and poor maintenance resulted in the company bosses involved and the architects of the building having charges brought against them. Polish law was changed so that large buildings have to undergo a technical survey twice a year.
Preventing collapse due to snow
Structural failures due to snow are usually the result of multiple factors. The roof’s shape, slope and construction will have an impact, as will its exposure to wind. Maintenance plays a part, and the type of snow that’s landing on the roof is important.
Fluffy, fresh snow will clearly weigh a lot less than very wet snow, and ice weighs a lot more than snow. If it’s safe to do so, removing snow and ice from “at risk” roofs is a good idea, though you may want to bring in the professionals.
You’ll also want to look for signs of stress in the roof and wall. You may hear cracking or creaking from the roof before it collapses. Doors and windows that are difficult to open, and sprinkler heads being pushed down are also signs that the roof is carrying an excessive load.
Now I’m not expecting any more snow in London, as the cold snap seems to be over, but we’ll potentially be seeing more dramatic weather patterns in the future, so the possibility of snow-related collapse is something we all need to keep in mind.
On a lighter note, did you know that it’s easier for the police to detect cannabis farms in snowy weather? Due to the large numbers of lamps needed to grow the plants, they simply look for roofs with no snow on them!
If you need assistance from a structural engineer on an upcoming project, please do get in touch with us.