Ensuring roof safety: Snow load monitoring and predictive maintenance

Winter storms bring with them the potential for roof collapses, especially in areas susceptible to heavy snowfall and ice accumulation. As each snowstorm adds layers to the roof, building owners face the challenge of determining whether their structure is at risk of overload and in need of snow removal. Traditional methods of manual inspection and guesswork often fall short, leaving property owners uncertain and vulnerable.

However, with the introduction of automated snow load monitoring systems, a new phase of proactive risk management unfolds. By leveraging technology to remotely detect potential damage risks, property owners gain the ability to take timely and informed action, mitigating the dangers posed by snow accumulation. 

This article explores various aspects related to snow overload on roofs, including the risks associated with snow accumulation, factors influencing snow distribution, the importance of snow load monitoring, and practical strategies for preventive maintenance. 

Snow accumulation factors: Assess the risks of snow load on your roof

Excessive snow accumulation on roofs poses serious risks, particularly when it transforms into ice. Weight varies depending on snow moisture and density, with wet snow being especially hazardous. If left unaddressed, snow can lead to ice dams, roof sagging, leaks, or even collapse.

Roof collapses result in extensive property damage, including structural harm, belongings destruction, and disruptions to businesses or homes.

According to the National Oceanic and Atmospheric Administration (NOAA), winter storms will cause $3.5 billion in property damage in the U.S. in 2020 alone, with roof collapses contributing to this figure.

But how to define the risks of snow accumulation on a roof? Below are some variables that influence the overall roof loads and collapse risks:  

Roof design

The design of the roof, including its roofline and any obstructions (such as chimneys or vents), affects how snow accumulates. Roof designs with flat or low slopes are particularly vulnerable, as they may allow snow to accumulate more easily. Older roofs or those with structural weaknesses are more susceptible to collapse under the weight of snow and ice. 

Building materials

The materials used in roof construction play a crucial role in determining its resilience to winter weather. Weak or deteriorating materials may be unable to withstand the added weight of snow and ice, increasing the risk of collapse.

Roof wind exposure

Snow distribution is heavily influenced by wind patterns. The windward sides of roofs typically gather more snow, while the leeward sides may accumulate less. This creates an uneven and potentially dangerous load distribution.

Temperature fluctuations

Rapid changes in temperature can exacerbate the risks of roof collapse. For example, sudden warming after a heavy snowfall can cause rapid melting and refreezing, further increasing the load on the roof.

Ice dams

Ice dams occur when snow melts on the roof and refreezes along the eaves, forming a barrier that obstructs drainage. This leads to water accumulation on the roof, elevating its load and adding to structural stress.

Roof age and neglected maintenance

Older roofs may experience wear and tear, affecting their ability to withstand snow loads. Lack of regular maintenance, such as clearing snow and ice from the roof or addressing potential structural issues, can heighten the risk of collapse during winter storms.

How much does snow weigh on my roof?

Understanding the snow load threshold for your roof is essential for safeguarding your property. The Insurance Institute for Business and Home Safety suggests that most well-maintained residential roofs can typically endure up to 20 pounds per square foot of snow. However, the maximum snow load capacity varies based on multiple factors, including geographic location. Regions prone to heavy snowfall may have roofs designed to support heavier loads. Exceeding the recommended snow load can lead to structural damage.

Yet, assessing snow load isn't solely about the depth of accumulation. The density of snow plays a crucial role, with wet snow weighing significantly more than dry snow. For instance, wet dense snow can weigh up to 25 pounds per cubic foot, whereas light fluffy snow may weigh as little as 7 pounds per cubic foot. Additionally, deeper snow tends to exert more pressure per cubic foot due to compression from the snow above. Therefore, it's imperative to consider both the thickness and type of snow accumulation to accurately evaluate roof safety.

To help you gauge when the snow on your roof might approach this weight limit, consider the following guidelines:

• Fresh snow: Approximately 10-12 inches of new snow is equal to about one inch of water, or roughly 5 pounds per square foot of roof space. Therefore, you could have up to 4 feet of new snow before the roof becomes stressed.
• Packed snow: About 3-5 inches of old snow is equal to one inch of water, or approximately 5 lbs. per square foot of roof space. If you have more than 2 feet of snow accumulation, it could be too much for your roof to handle.
• Ice: Remember that a single inch of ice is equivalent to one foot of freshly fallen snow.‍
• Total accumulated weight: If you have two feet of old snow and two feet of new snow, the combined weight could reach up to 60 lbs. per square foot of roof space. This exceeds the typical snow load capacity of most roofs.

How snow loads are calculated

Determining the snow load on a flat roof involves taking a test sample of the roof snow. Ascend to the roof and extract a cubic foot of snow down to the roof deck, collecting it in a container. Then, melt the snow and calculate its volume in water. This enables the calculation of the snow's weight per square foot on the roof, using the formula:

Refer to the snow load chart below for a rough estimate of the weight of snow on a roof.

While further calculations are required for pitched roofs, flat roofs are particularly susceptible to snow load damage. For pitched roofs, utilizing a snow load calculator is recommended. 

In the absence of automated monitoring systems, which eliminate the need for manual weight measurements, this method proves effective. However, it necessitates regular execution and meticulous attention to detail, especially during result interpretation. Incorrect execution can return varying results among individuals, making this method time and labor-consuming.

On the contrary, automated snow load monitoring systems simplify and optimize structural stress evaluation. These systems eliminate the need for manual measurements, reducing the risk of human error and ensuring consistency in data collection. By leveraging advanced technology, property owners can enhance safety measures, minimize risks, and protect their investments more effectively against the potential damage caused by excessive snow loads on roofs.

Automate snow load calculation: preventive maintenance with low effort 

Prylada offers an automated snow load monitoring solution designed to ensure comprehensive control over roof load forces with minimal effort. This solution provides real-time data through connected sensors, enabling prompt action if snow load levels approach critical thresholds. Strategically installed intelligent sensors continuously measure snow weight on the roof structure, ensuring accurate answers to the following questions: 

• If you need to clear snow.
• When you need to do it.
• On which part of the roof (based on the sensor location).

Moreover, the possibility of integrating with your building management systems enhances oversight of structural integrity, effectively mitigating the risk of roof collapse.

The solution functions include:

• Monitoring and ensuring snow load remains below the building structure's capacity.
• Assessing the level of risk associated with snow load accumulation.
• Preventing potential risks linked to snow load on organizational building structures.

Prylada's components facilitate round-the-clock automated snow accumulation monitoring, complete with intuitive charts and SMS alarm notifications to mobile devices. 

By embracing remote snow load monitoring, you can fortify safety and resilience for your structures. With full information on snow accumulation levels, you'll know precisely when to remove excess snow, eliminating the need for hazardous manual inspections and guesswork. It's all about making data-driven decisions to ensure the structural integrity of your buildings.