Planning to build this year? All-steel structures require a thorough knowledge of precipitation loads, especially in the wetter climates of the northern U.S.

Snow Loading

Wind and drainage capabilities can displace a lot of rooftop snow, causing the ground snow load to be larger than any roof snow load. Snow sliding and drifting are regular occurrences which should be considered if you live in a snowy area. If a higher pitched roof exists, it can allow snow to drift to the lower level, thus increasing load on the lower roof. Walls and parapets see a lot of snow loading. Total rooftop area and wall and parapet heights are major factors in determining snow load.

The maximum potential snow density accepted for a structure’s roof at a particular time is known as the design snow load. The use of live load is largely dependent on the structure’s use, but snow load corresponds to specific areas on the structure. The design snow load number is impacted by the accepted ground snow depth in a community. Properly engineering any pre-fabricated structure to its ideal design snow load entails the use of precise calculations in conjunction with ground snow amount. Major considerations include flat roof snow load, the ground snow load total quantity, as well as temperature and exposure of the structure.

For design purposes, it is important to be aware of the results of uneven snow loads on gabled or hip roofs. Almost any all-steel structure can achieve precise loading with the consideration of the total building area, roof pitch, and flat slope snow load quantities.

Rain Loading

Proper and precise roof loading sums can only be ascertained by tallying all rain and rain-on-snow loads with building calculations. This is crucial because in many regions of the U.S., snow storms can quickly change to rain. Any snow present on top of a given steel roof, especially one with a flatter slope, will tend to soak up excess water and thus prevents the flow of water. Rain load is the rainfall mass on top of the roof that may accumulate as a result of inadequate roof drainage. Using extra rooftop support and augmenting roof slope can lessen the heavier roof load from rain. Outlying channels instead of inner channels can also minimize roof warping from rainfall weight. Quick water movement from a steel structure can guarantee the entire structure’s viability.

Partial Loading

One final aspect to consider when talking about snow load is partial loading. If you use a multi-span pre-engineered structure instead of a clear-span, partial loading can generally be contained in structural supports, such as frames and purlins. There are some spans of a given steel structure that are engineered for maximum snow load, leaving other spans to necessitate only minimal loads. You should carefully plan for the proper application of snow load calculations.