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An investigation of unbalanced or drifted snow loading on single gable roofs is presented. A database of 28 case histories was developed and analyzed to identify trends and key parameters for this type of roof snow drift. The analysis suggests that roof slope, roof width (i.e., ridge to eave distance), and ground snow load are the key parameters influencing drift size. Furthermore, substantial drifts near the eaves of low sloped roofs (slope less than 15°) are possible, particularly if the width is large and the ground snow load is moderate. A number of simple relations were developed that can be used to predict the total height for low sloped roofs. Predicted values from these relations were compared with observed values to gauge their relative accuracy. It is felt that the simple relations developed herein are an improvement over current code provisions, specifically for low sloped gable roofs. It is expected that they will be the basis for proposed changes in building codes and load standards. The implications of the proposed changes are illustrated in a design example.
O’Rourke et al. (Mon,) studied this question.