Snow loads on sloping roofs: two pilot studies in the Ottawa area

Abstract

The results of two pilot studies are presented: one concerning snow on farm roofs in the Ottawa area carried out in 1966, and the other an eight-winter investigation of the influence of surface roughness and slope on snow accumulation on nine 2.4 m × 2.4 m unheated, north-facing experimental roofs built in a sheltered woods at the National Research Council Canada in Ottawa. The results indicate a trend towards reduced snow density as slopes increase and a smaller accumulation of snow on smooth (metal) surfaces than on rough shingled roofs as slopes increase. More data on full-sized roofs across Canada are required to verify this. It is suggested that a less conservative slope-reduction relation might be considered for smooth roofs in the Ottawa area and for other areas with similar climate. Key words: snow loads, sliding snow, sloping roofs, snow depths, snow densities, surface roughness, pilot survey.