Metal buildings are widely recognized for their strength and durability, making them an ideal choice for cold and snowy climates. However, in order to fully reap the benefits of these structures, regular roof maintenance and snow removal are crucial. Several key factors need to be considered for optimizing metal panels in such conditions. This includes proper design during the initial construction phase, which ensures that drift zones, cold spots, and hot spots are avoided within the roof system. This is important to prevent water from freezing and thawing, which can result in dangerous ice buildup.
It is important to conduct roof inspections before winter arrives to address any existing issues before they worsen due to snow and ice accumulation. While metal roofs are typically designed to perform well in winter conditions, heavy snowfall can pose risks to buildings and the people inside and around them. This article will discuss the weather conditions that can impact metal roofs and walls, and provide steps to mitigate potential negative effects in areas prone to snow and ice.
1. Anticipate Snow Load
In regions where snowfall occurs, roofs of all types can accumulate snow, resulting in an increased weight that the structure must support. This weight, known as snow load, can pose a danger to both the structure and its occupants. If the weight of the snow exceeds the structure’s capacity to bear it, the roof or even the entire structure may collapse.
When designing a metal roof, it is important to consider the specific levels of snow accumulation required by building codes in the area. The required levels typically range from 4.5 to 9 kilograms per square foot, but can exceed 18 kilograms per square foot in some locations. Structural engineers can design the roof structure to determine the loads acting on the roof based on the snow load. It is important to consult the International Building Code (IBC) and state and local codes for guidance based on the location.
Snow density can vary greatly, ranging from light and fluffy to wet and heavy. This variation makes it difficult to accurately translate the amount of snow to weight. As a conservative estimate, less than 2.2 kilograms per square foot per inch of depth can be used for very wet or heavy snow.
If a roof is designed to accommodate a snow load of 9 kilograms per square foot, any accumulation over 4 to 5 inches should be cause for concern. To determine the building’s carrying capacity and a reasonable range of snow density and weight, a structural engineer should be consulted. The most important takeaway is to be aware of the weight the structure can bear and to remove snow to keep it within safe limits.
2. Prevent Sliding Snow
Snow shedding is an important process to prevent the accumulation of snow beyond a building’s structural limits. However, the shedding of accumulated snow can pose a risk to people and property. It is important to strike a balance between snow load and shedding, taking into account geographical factors, building materials, and roof design.
The pitch of a roof plays a significant role in the accumulation of snow. Roofs with a higher slope, greater than 3:12, can cause snow to slide down at an accelerated pace, which can be dangerous. This sliding snow can damage property and injure people. The weight of the snow can also cause icicles formed on eaves to fall, which can be hazardous. Additionally, if the sliding snow falls on exterior gas pipes, it can rupture them, leading to a fire hazard.
Low slope roofs, less than 3:12, offer less resistance to sliding due to low friction. Metal roofing with striations and embossing can provide better resistance to sliding, especially when running traverse to the slope. Installing metal panels with snow retention devices on a steeply-sloped roof is recommended. This helps shed snow and ice from the roof and protects the structure from excessive snow loads. Although the installation may seem complicated, it is a worthwhile investment.
3. Prevent Ice Dams
Ice dams are formed when ridges of ice accumulate at the edge of a roof, blocking the proper drainage of melting snow and resulting in potential damages to structures. The main cause of ice dams is often attributed to flaws in the building’s air barrier. When warm air from indoors escapes through the roof, it warms up the roof sheathing. This increase in temperature then causes the underside of the layer of snow on top of the roof to melt. Understanding the causes of ice dams is crucial in order to take appropriate steps to prevent their formation and avoid costly damages.
Ice dams on metal roof
Ice dams can form on roofs when melted snow moves down the slope towards the eaves and freezes. Over time, these ice dams can thicken and trap water, leading to potential damage to the roof system or leaks. One solution to prevent ice dams is to use a peel and stick membrane on the roof deck, extending from the eave to about 3 feet up-slope from the exterior wall. Another preventive step is to frame the roof with raised heel trusses, and avoid valleys and gutters that are at or above the roofing plane. These considerations should be prioritized during the design, installation, and maintenance of a metal roof.
4. Use Retention Systems
Snow and ice buildup on rooftops can be dangerous and lead to sudden avalanches. To prevent such risks, retention systems such as snow fences, bars, or guards can be installed. These systems are designed to either melt the snow and ice or allow it to fall off in smaller amounts, reducing the likelihood of a hazardous situation.
However, it is crucial that these snow retention systems are carefully engineered and installed correctly. Poorly installed or inadequate systems may not effectively manage snow and ice buildup, leaving rooftops vulnerable to avalanches. This could potentially cause serious injury or damage to property.
To ensure the effectiveness and safety of snow retention systems, it is recommended to consult with professionals who have expertise in engineering and installing such systems. This can help ensure that the system is properly designed and installed, taking into account factors such as the roof pitch, type of roofing material, and local climate conditions. Ultimately, proper installation of snow retention systems can help mitigate the risks associated with snow and ice buildup on rooftops.
5. Protect Roof Attachments
Sliding snow can exert a significant amount of force that can cause attachments, such as exhaust vents, to be dislodged from roofs. This can result in serious damage and pose a threat to individuals below. To avoid such a scenario, it is recommended to install rigid vent pipes as high up on the roof slope as possible. This will help reduce the shear load caused by sliding snow, thereby minimizing the risk of attachments being torn off.
In situations where it is not possible to install rigid vent pipes at a higher elevation, an alternative solution is to implement a snow retention system. This system is designed to prevent sliding snow from accumulating and sliding off the roof, which can cause significant damage to the building and pose a safety hazard. By using snow retention systems, exhaust vents and other roof attachments can be protected from the force of sliding snow, ensuring the safety of the building and its occupants.
6. Proper Snow Removal
Snow accumulation on the roof can pose a serious threat to the safety of the loads it carries. To ensure that the loads are at safer levels, it is important to remove the standing snow after a winter storm. This is particularly critical for older homes with poor attic insulation, as it can result in the formation of ice dams.
However, removing snow from the roof requires caution to prevent causing damage to the metal roof with metal or sharp tools. To avoid such damage, experts advise removing only the excess snow and leaving a thinner layer on the roof to melt and disperse naturally. When removing snow from the roof, it is essential to do so uniformly from the entire surface of the roof, starting from areas with accumulated snowdrifts and then moving evenly across the roof.
7. Additional Consideration
1. Roof Material and Surface Color
Metal roofs have a unique property of rapidly absorbing and effectively radiating heat. This characteristic is further amplified when darker colors are used, as they enhance the absorption of solar energy. However, this can pose a challenge during snowy weather, as the combination of UV light and heat loss through the roof can cause the snow to melt and lose its solid state.
Ice damming can be prevented by ensuring that the roof system is adequately sealed and insulated. When a roof is not properly sealed and insulated, it can lead to the formation of ice dams. These dams form when snow melts and refreezes repeatedly, creating layers of ice that can cause snow to slide off the roof, regardless of the type or color of the roofing material. Therefore, it is important to ensure proper sealing and insulation to avoid ice damming and the associated risks of snow sliding.
2. Watertightness
To prevent water, particularly melted snow, from penetrating a building’s structure, it is crucial for low-sloped roofs to have watertight panel seams. This can be achieved by utilizing panels that have successfully passed the ASTM 2140 water head test or FM 4471 Appendix G water test. Additionally, it is advisable to consider using water-resistant underlayment for all roof slopes. By implementing these measures, the risk of water damage can be minimized, and the structural integrity of the building can be maintained.
3. Roof Layout
Snow accumulation and increased snow load can be a problem for roof designs featuring valleys and slope changes. Additionally, dormers that extend from a larger roof area and have significantly unequal areas can cause unbalanced sliding snow, which can be damaging to the roof structure. This imbalance may result in the tearing open of standing seams and displacement of panels.
Furthermore, drifting snow can remain in areas behind HVAC units, perimeter walls, and solar and photovoltaic (PV) panels. These areas are particularly susceptible to snow accumulation and increased snow load, which can further contribute to the potential for damage to the roof structure. As a result, it is important to consider these factors when designing and constructing roofs, in order to minimize the risks associated with snow accumulation and unbalanced sliding snow.
4. Roof Maintenance
Regular roof inspection and maintenance work is crucial in regions that receive heavy snowfall. This is because it is essential to remove any standing snow and prevent the formation of ice dams to avoid any damage to the metal panels. Taking these measures will help to ensure the safety and longevity of the roof. Failure to do so can result in significant damage to the roof, which can be costly to repair. Therefore, it is necessary to prioritize the maintenance of the roof in areas that experience heavy snowfall.
5. Warranty Considerations
When facing issues with roofing materials, it is recommended to seek advice and guidance from the manufacturer of the product. Not only can they offer recommendations, but they can also help with any potential warranty claims. It is important to keep in mind that using products or tools that are not approved by the metal panel manufacturer could potentially void the product warranty.
To ensure that the warranty for the metal panel is valid, it is advisable to review the warranty terms provided by the manufacturer. By doing so, one can identify any specific requirements or restrictions that must be followed when installing or using the product. It is also crucial to verify that the materials and tools being used are approved by the manufacturer, to avoid any issues that could invalidate the warranty.
Taking these precautions can help to ensure that any issues with the roofing materials are addressed promptly and effectively. Consulting the manufacturer for guidance and adhering to their recommendations and warranty requirements can also help to prevent potential problems from occurring in the first place.
FAQs
How does one anticipate snow load when laying metal roof panels in colder regions?
When it comes to designing a metal roof, structural engineers must take into account the relevant code requirements for snow accumulation levels in the building’s location. These requirements can range from 4.5-9 kg psf up to over 18 kg psf. To ensure compliance with the appropriate standards, it is advisable to consult the International Building Code as well as any relevant state and local codes for guidance based on the specific location of the building. By doing so, engineers can ensure that the metal roof is designed to withstand the expected snow loads in the area and will be able to provide the necessary protection and structural stability.
What are ice dams?
Ice dams are a type of obstruction that forms along the edge of a roof. These obstructions are essentially ridges of ice that prevent melting snow from draining off the roof. As a result, the water pools behind the ice dams and can cause significant damage to the roof structure. This damage can be quite costly to repair and can even pose a safety risk if left unaddressed. It is therefore important to take steps to prevent the formation of ice dams and to address them promptly if they do occur.
What are some examples of retention systems in roofs?
There are various tools and structures that are commonly used to deal with snow and ice accumulation. One such example is snow fences, which are installed in strategic locations to help prevent snow from accumulating in certain areas. These fences work by creating barriers that slow down the wind and cause snow to settle on one side, reducing the amount that accumulates elsewhere. Similarly, bars and guards can be installed on roofs to prevent snow and ice from accumulating in large amounts. These structures are designed to allow for gradual melting and small-scale falling, reducing the risk of sudden heavy loads on roofs that can lead to damage or collapse. These measures are effective in managing snow and ice accumulation, ensuring safer conditions during snowy weather.