how to calculate snow load on a flat roof

When designing the roof of a building, engineers must consider the weight of various loads that could potentially accumulate on its surface. One of these loads is snow. In areas where snowfall is common, it is crucial to calculate the snow load on a flat roof to ensure that it remains stable throughout the winter season. In this article, we will go over the necessary steps to calculate snow load on a flat roof.

Gather Necessary Information

Before anything else, you need to gather relevant data about your location and the roof you will be calculating the snow load for. You will need to know the average snowfall rate in your area, the roof's dimensions, pitch, and its maximum expected drift height. You can obtain this information from local weather records and building plans.

Determine the Shape Coefficient

The shape coefficient is a crucial factor in determining the snow load on a flat roof. It is a value between 0.8 and 1.2 that accounts for the shape of the roof and the angle at which snow will accumulate on it. The coefficient varies depending on the roof's slope and shape. For example, a flat roof will have a shape coefficient of 1.0, while a shallow-pitched roof will have a coefficient closer to 1.2. You can consult technical manuals or local building codes to determine the appropriate coefficient for your roof.

Calculate Uniform Load

The next step is to calculate the uniform load, which represents the weight of accumulated snow spread evenly across the roof's surface. Start by multiplying the shape coefficient by the roof's projected area. Then, multiply that result by the expected snow depth. The final number will be the uniform load on the roof in pounds per square foot.

Factor in the Drift Load

Finally, you need to factor in any potential drift loads that could occur due to wind patterns in your area. Drift loads happen when snow accumulates into higher piles on certain areas of the roof due to wind. To calculate this load, multiply the uniform load by the drift height. This will provide you with an estimate of the extra weight that certain parts of the roof could experience.

Conclusion

Calculating snow load on a flat roof is critical to ensure your building's structural integrity and the safety of its occupants. By gathering relevant information, determining the shape coefficient, calculating the uniform load, and factoring in any drift loads, you can estimate snow's weight on your roof. Always consult local building codes and safety measures to ensure that your building's design can withstand the expected snow loads year after year.