Snow-Loaded Building Collapses After a Jump: Roof Snow Load Explained

A man jumps on the ground beside an old, run-down building with a thick blanket of snow on its roof, and a moment later the whole structure comes down. Shared in April 2014 as a man demolishing a building by jumping, the clip is really a lesson in how much weight snow puts on a roof, and how little it takes to tip a tired building over the edge.

The building collapse video

The footage was uploaded to YouTube by ecksdannyjecks under the title "building collapse from jump" and picked up by Gizmodo. The building is visibly deteriorated and loaded with snow. A man jumps on the ground nearby, and the structure gives way.

It looks like cause and effect, and the timing is perfect for a joke. Structurally, though, the jump is the smallest part of the story. A building that falls after a thud on the ground was already carrying almost all the load it could take, and the snow on its roof had done most of the work.

How much snow weighs on a roof

Snow looks light, but it adds up fast. Maine's emergency management agency gives these rules of thumb per square foot of roof:

• Fresh snow: 10–12 inches (25–30 cm) equals about one inch of water, or roughly 5 lb per square foot (about 24 kg/m²).
• Packed or old snow: only 3–5 inches (8–13 cm) weighs the same 5 lb.
• Ice: one inch of ice weighs as much as a foot of fresh snow.

The Insurance Institute for Business & Home Safety estimates that a typical roof can carry about 20 lb per square foot of extra weight. Two feet of old snow topped by two feet of new snow can reach around 60 lb, well beyond most roofs. Older or previously damaged roofs can fail far sooner, which is exactly the kind of building in the video.

Famous snow-load roof collapses

Snow loads have brought down far bigger structures than an abandoned shed.

• Katowice Trade Hall, Poland, 28 January 2006. The roof of the exhibition hall in Chorzów collapsed during a pigeon fair with about 700 people inside. Sixty-five people died and more than 170 were injured. Investigators found a flawed, cost-cut design and a roof left uncleared of snow and ice, overloaded by more than 100%. Poland later required technical surveys of large buildings twice a year.
• Metrodome, Minneapolis, 12 December 2010. About 17 inches (43 cm) of snow fell on the city. Wind kept crews off the inflated roof, the centre sagged, and three panels tore open before dawn. The Minnesota Vikings' game against the New York Giants was moved to Ford Field in Detroit.

Warning signs of roof overload

Buildings usually complain before they fail. Maine's guidance lists the signs to watch for:

• sagging sections of roof or ceiling, and severe leaks
• cracked or split timber, bent or rippled supports, cracks in walls or masonry
• doors that pop open or suddenly stick
• sprinkler heads dropping below ceiling tiles, or bowed pipes and conduit
• creaking, cracking or popping sounds

Leave the building at once if you notice any of them, and have it inspected. To clear snow from a pitched roof, work from the ground with a roof rake, start at the edge, take small amounts and leave a couple of inches in place to protect the shingles. Keep aluminium rakes well away from power lines.

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