Snow Drifts and Sliding Snow 


A lean-to (single-slope) addition is a smaller attached PEMB module that ties into the side of a main building and uses a mono-slope roof draining away from (or toward) the primary frame line. It is a cost-effective way to expand usable covered area—such as loading docks, storage, equipment rooms, service bays, or sheltered walkways—without increasing the full width of the main building or requiring major changes to the primary framing layout.

When a lean-to is attached to a taller main roof, snow drift on the lower roof and sliding snow can become governing actions and must be included in the snow-load calculation. The step in roof height promotes drift accumulation along the interface, and sliding snow from the upper roof can deposit on the lean-to roof, increasing local demand on purlins, rafters, and edge details. MkaPEB automatically calculates these drift and sliding-snow effects and applies the corresponding load cases in the structural model.


Drifts on Lower Roof


Sliding Snow on Lower Roof