If you own a pitched roof, you should be aware of the snow load it supports to prevent damage to your eaves, vents, and the roof itself. It can be determined with a simple tool that considers the roof’s rise and run, its pitch, ground snow loads for your area, etc.
Roof Pitch
Knowing how much your roof can bear in snow load is essential to prevent damage to the eavestroughs, vents, and roofing structure. However, the amount of snow your roof can support depends on several variables, including your building’s location and local weather conditions. For example, ground snow loads can reach 450 pounds per square foot or more in the Sierra Nevada Mountains, where snow is known as “Sierra Cement.”
The roof snow load calculator considers these variables, which compares your building’s maximum permitted snow load to the actual snow load it experiences. The calculator also considers the rise and run of your roof, determining how much force is exerted on it. It is because snowflakes might look the same, but they can have very different densities depending on their moisture content and other factors.
Roof Length
In addition to roof pitch, the length of your roof also plays a role in snow load. Roofs that are longer than a single-story home will have to carry the weight of more snow than shorter roofs.
Ideally, roofs should be designed to support the maximum ground snow load that occurs in the specific geographic area where the house is located. Unfortunately, this is not always possible, and structural engineers use various factors to determine a roof’s design snow load.
These factors include the terrain where a building is built, wind conditions, temperature changes, and rainfall. Rainfall can cause snow to thaw, transitioning it from loose, powdery snow to dense, wet snow that puts more pressure on the structure of a roof.
A general rule of thumb is that most residential roofs can withstand up to 20 pounds per square foot of snow without experiencing significant stress. However, the snow’s thickness and the old snow’s age play a big part in that number, and even two feet of wet, packed snow could exceed the roof’s load-carrying capacity.
Roof Width
Nothing is much lighter than a snowflake, but those delicate feather-weight particles become different when massing together. As such, structural professionals must know how to calculate roof snow loads for their projects correctly.
That is especially true in areas with high snowfall. Often, roofs in these areas require greater spans of rafter than those of homes built in other regions with lower snowfall.
That’s why building codes across the United States have different snow load requirements based on each region’s record snowfall. These requirements dictate the amount of snow a home’s roof can hold without suffering damage to eaves, vents, and the roof’s structure. A simple online snow load calculator can help determine your roof’s maximum snow loading. You can enter various requested variables, such as your roof pitch, location, and other factors, to determine how much snow your roof can support.
Roof Depth
Knowing the maximum snow load your roof is designed to support is essential. But, the number can take time to determine. Luckily, there’s a tool that can help you with this.
This calculator allows you to input the rise and run of your roof, ground snow load for your city, roof exposure, roof type, and other factors. Then, it uses formulas based on national structural engineering codes to calculate your snow load.
One of the most significant variables in the snow load calculation is the moisture content of the snow. It’s not just that some snow is powdery and light while others are wet and heavy; it can melt during the day and re-freeze at night, adding extra weight. The more moisture in the snow, the more force it exerts on your roof. Inspecting your roof regularly is crucial, paying particular attention after back-to-back blizzards.
