Conditions of snow sliding on metal sheet roofs

It is observed frequently in heavy snow districts that snow on roofs breaks and slides down. Usually this is considered as a favorable phenomenon in the decrease of snow load on sloping roofs, but on the other hand, it brings about various problems. This study is aimed to investigate the conditions of snow sliding on the sloping roofs of private houses and other buildings roofed with metal sheet. The results of experiments were : 1) Snow sliding is influenced by the air temperature. Generally, it starts when the temperature rises above 4°C. 2) The temperature variation after snow fall is an important factor. Unless the lowest temperature is below about -1°C, snow sliding occurs easily. 3) Snow does not slide easily on old roofs, but in some cases, sliding occurs within snow layers under some conditions. 4) Overall sliding is caused by successive local sliding.