Snow load is one crucial factor to consider in structural designs, particularly in regions with heavy snowfall. Accurate snow load assessment helps prevent structural failure and ensures the buildings are safe.
Along with the right calculations, considering key factors like roofing design, material, elevation, and much more guides engineers to build a highly tailored design that withstands the weight of accumulated snow.
Learn more about this topic to enjoy a leak-free winter under a safely built roof.
What Is Snow Load?
Snow load is nothing but a pile-up of snow or ice spread over the building’s roof. So, the roof design, style, and material should hold the snow load pressure or force without any damage to the building.
Snow is a live load that changes over time and its density determines the pressure snow puts on the roof. Some snow can be powdery and light, which might be easily removable. But, wet and compact types of snow are quite difficult to clear.
So, based on the snow type, the density varies. Here is a table to show the snow type and its density.
| Type of Snow | Pound Per Cubic Square Foot |
| Ice | 57.25 |
| Wet and heavy ice | 46.82 |
| Wind-packed snow | 23.41 |
| Settled snow | 15.61 |
| Damp, freshly fallen snow | 6.87 |
| Freshly fallen dry snow | 3.75 |
How to Calculate Snow Load
Multiplying the snow’s depth (in feet) by the weight of a cubic square foot of snow (in pounds) is the easiest way to calculate the snow load.
However, ASCE also shows the right direction for the structural engineer to calculate the Flat roof snow load (Pf).
- Pf = 0.7 * Ce * Ct * Is * Pg
Here,
- Exposure factor Ce
- Thermal factor Ct
- Important factor Is
- Ground Snow Load Pg
Snow Load and Roofing Design
Choosing the best roofing design to sustain the heavy snow load will be an obvious goal for many. In that case, considering and crosschecking the factors affecting the roof can prevent snow load damage and make the goal achievable.
- The Amount of Snowfall in a Single Storm: Compare the amount of snow in a blizzard. It is comparing 30 inches of snow throughout the winter vs. a blizzard that drops 30 inches in 24 hours.
- Wind Gusts: Drifting snow may create tall snowdrifts that put more pressure on the specific areas of the roof.
- Temperature Fluctuations: The temperature fluctuations in the afternoon and nighttime can transform the light snow into much denser and wetter snow.
Predicting nature is impossible, but considering these factors helps to determine a better roof design for snow load.
Roof Pitch
Steeper roof pitches are highly recommended for areas with heavy snowfall. Because steeper pitches allow the snow to shed more easily on the roof structure.
The ideal and safer pitch ranges from 3:12 to 6:12. According to FEMA, a subtle 10-degree or 2:12 pitch reduces the snow accumulation effectively. So, try to follow these guidelines to improve the safety.
Roof Style
The two popular roof styles to prevent snow accumulation are Gable and Hip roofs.
Gable Roofs: This is a common type of roofing style that everyone opts to tackle snow load. The design comes with steep angles and sheds water, snow, and other debris very quickly.
Adding to this, gable roofs are more affordable, quickly maintained, and provide enhanced space inside the room.
Hip Roofs: Hip Roof and valley roofs are well-known for their ability against water and snow buildup. This design is also similar to classic gable roofs but with the four sides meeting at the peak to support heavy loads.
The slanted sides reduce the risk of leaks and water damage. It also offers excellent stability, wind resistance, and durability over time. That’s why hip roofs are considered the most suitable for managing snow loads.
Roof Material
What could be the best roofing material to prevent snow load? Classic Asphalt roofs will not work in this brutal winter, so you can choose metal.
Metal is an ideal choice for managing heavy snow loads because it can withstand heavy snowfall and protect the building throughout the winter.
Roof Obstructions
So far, you have learned about some important factors that help to prevent and manage the snow load. However, this is one of the essential things to avoid when planning to manage snow loads.
Roof obstructions can block the pathway of the snow and make it very tough to shed and slide. It also increases the pressure on the roof.
Hence, instead of choosing roof obstructions, prefer modern heated roof panel systems. These designed roofs are automated and gently warm the snow and ice on the roof.
Ground Snow Load vs. Roof Snow Load
Ground and roof snow loads are the two extreme things to compare. It’s because there is no connection between the ground and roof snow accumulation level.
But, measuring ground snow load can help to calculate the roof snow load. Let’s know how it is possible, here.
Ground Snow Load
The ground snow load (PG) is used in the determination of the roof snow load of a site. This number is usually based on historical measurements taken at different weather stations.
So, if it is winter, make sure to contact your local building department to determine the local ground snow load. This helps you to calculate the exact amount of snow.
Roof Snow Load
Roof snow load is nothing but the pressure exerted by the increased amount of snow or ice. Multiplying the density by depth of snow or ice is the easiest way to calculate roof snow load.
Snow Load Capacity of the Structures
Awareness of your barns and other buildings’s snow load capacity ensures your family’s safety. However, the snow load capacity of the structure is determined by the roofing and other building materials and the construction style.
In general, residential roofs are built to withstand an average amount of snow load, around 20 to 30 pounds per square foot (psf). It also varies according to the geographic location of that particular region.
In areas of India that get heavy snowfall, like Himachal Pradesh and Jammu & Kashmir, there are strict building rules to help houses handle the weight of the snow. Homeowners in these regions should talk to local building officials or structural engineers to check how well their roofs can hold up under heavy snow. Following these rules and getting expert advice can help keep homes safe and strong during winter weather.
Conclusion
In conclusion, snow load is an essential consideration in the structural design process, particularly for heavy snowfall regions. So, ensuring proper safety measures and prior planning of roofing designs help to manage the load effectively.
Utilise the calculations and other tips in this blog to prevent the beautiful roofs of any building.