Determination of wall height to capture windward drift snow on flat roofs

A new taller building adjacent to an existing building with a lower roof is a relatively common situation. The new building provides a snow source area, which results in snow drift atop the lower roof which likely was not anticipated in its original design. Since it is usually difficult to retrofit the existing roof structure, a solid wall can be considered to capture the expected snow transport on the upper roof. Using field measurement on snowdrift development around solid walls, ASCE 7 provisions and Drift Ratio parameter, two approaches based on average or conservative values are studied to determine the required height of the solid wall. The results indicate that conservative values provide arguably unrealistic values, while the average or combination of average and conservative values provides reasonable wall heights.