Call us today at (716) 807-8271
Our company sits in Western New York, an area renowned for major snow events. Buffalo gets over 90 inches of snow each year, on average. Some storms have dropped over 80 inches in a single event. Snow load is one of the most critical factors in designing the buildings we supply. Snow loads may seem simple, but they are not. Many factors need consideration. They ensure the building can handle the right snow load.
The process of designing for snow load begins with determining the ground snow load. For most of the U.S., the ASCE 7 standard maps this information. It provides minimum design loads and criteria for buildings and other structures. In areas with high snowfall variability, the Authority Having Jurisdiction (AHJ) may require a case study. So, it is vital to contact the AHJ when designing a building.
Engineers use the ground snow load to calculate a building’s flat roof snow load. Roof snow load is usually less than the ground snow load. That’s because less snow accumulates on a roof than on the ground. Several factors influence the calculation of roof snow load:
Snow Exposure Coefficient (Ce) depends on the roof’s snow exposure and the terrain category.
Roof Snow Exposure
Terrain Categories
The snow exposure coefficient varies depending on these conditions. For example, roofs in open, exposed terrain (Category D) have the lowest exposure factor. Wind blows snow off these roofs. Sheltered roofs surrounded by obstructions retain a greater amount of snow. They have the highest exposure factor.
Thermal Factor (Ct): The thermal coefficient considers heat transfer through the roof.
Snow Importance Factor (Is) is determined by the building’s Risk Category
Unbalanced and Drifting Snow
Unbalanced snow occurs due to variations in roof shapes and geometries. In a gabled building, snow tends to accumulate on one side of the ridge. The design must account for this.
Snow drifts form from different roof heights in a building, or when attaching to a building with a different eave height. These variations can cause significant snow accumulation. They must be considered in the design process.
Designing for snow loads is complex. It requires careful consideration of many factors. These include ground and roof snow loads, exposure, thermal conditions, and importance factors. By understanding these elements and consulting the AHJ, we can ensure that metal buildings are safe and resilient.