Snow Drift On Gable Roofs

The wind causing snow transport and.

Snow drift on gable roofs.

The amount of additional snow load or surcharge depends on the difference in height of the two adjacent roofs and the lengths of roof perpendicular to the drop in height. Gable roof drifts slope limits there is a range of roof slopes which require gable drifts lower limit is on 12 upper limit is 7 on 12 39 gable drifts upper limit observations by ttea unbalance for 6 on 12 less consistent with max slope of roof step drifts 1v 2h angle of repose of drifted snow 30 40. For gable roofs a rectangular drift surcharge was prescribed and the rectangular shape remained unchanged everywhere along the ridge line. Windward snow drifts occur when wind blows snow from a lower elevation roof towards the wall of an adjacent higher roof.

Gable roof is a typical roof style which is commonly used in many countries. The gable roof exhibited a slightly higher accumulation coefficient than the flat roof. Resulting drift formation was envisioned as perpendicular to the roof step para pet wall or ridgeline. An analysis of snowdrift patterns and accumulation coefficients which are representative of the depth of snow cover for flat and gable roofs showed that accumulation coefficient decreases in accordance with increases in wind speed.

Snow can either blown from the low side of the roof towards the high side or is blown off the higher area of the roof onto the lower projected side. In snowy regions an accurate prediction of drifting snow loads on gable roofs is essential for structural designs. Current provisions of snow load in load standards codes are primarily based on limited case histories and engineering judgment.