How much does snow weigh?

Valtava lumimäärä on tippunut ulkorakennuksen katolta.

Anyone who has been shovelling snow knows that wet slush is heavier than fluffy snow in sub-zero temperatures. Does snow get heavier when the temperature rises above zero? Should you worry about the snow load on the roof when it gets milder?

At above-zero temperatures, snow feels wetter and becomes compressed. This does not mean that your roof carries more weight per square metre in milder weather, however, as snow absorbs little or no moisture from the air.

If it starts raining, the situation changes. A thick layer of snow can absorb rainfall amounts of up to dozens of millimetres before the water starts trickling through the snow. If there is 60 centimetres of snow on the roof, rain can increase its weight by 30 kilograms per square metre.

Residents of single-family houses need not worry as their roofs are designed to carry thick layers of snow, no matter how wet, whereas industrial buildings and sports halls with a large frame can be at risk.

If you live in a single-family house, the key is looking after your own and other people’s safety. You must make sure that snow sliding off the roof does not cause hazards. Snow and ice are heavy and can fall down in a flash. You should also never take it into your own hands to climb up to the roof and start pushing the snow down.