Metal buildings are known for their strength and durability, making them a popular choice for cold and snowy climates. However, to ensure these roofs perform optimally, regular maintenance is crucial, including snow removal and inspections to mitigate any risks. Here, we explore key considerations for maintaining metal roofs in harsh winter conditions, covering everything from design tips to snow load management and safe snow removal.
1. Optimizing Roof Design for Snowy Conditions
Proper initial design is essential for metal roofs intended to withstand heavy snow. A well-designed metal roof system can minimize drift zones and prevent cold and hot spots that lead to ice buildup. Additionally, inspecting roofs before winter begins allows any existing issues to be addressed before snow and ice can exacerbate them. This preparation ensures the roof’s structural integrity and prevents small problems from becoming significant risks.
2. Key Factors Affecting Metal Roof Performance in Snowy Climates
Snow Load Anticipation
In snowy areas, accumulated snow adds substantial weight (known as “snow load”) to the structure. If this weight exceeds the roof’s bearing capacity, it can pose serious risks, including roof collapse. Structural engineers consider regional snow load requirements, often specified by the International Building Code (IBC) and local regulations, to design roofs that can withstand these stresses. Snow density varies (light and fluffy versus wet and heavy), with denser snow posing a greater load. For instance, wet snow may weigh up to 2.2 kg per square foot per inch of depth, so roofs must be designed accordingly. A structural engineer can determine the safe load capacity for a specific roof and provide guidance on snow depth limits, helping building owners stay within these safe limits.
Preventing Sliding Snow
Sliding snow, or “shedding,” can be dangerous, leading to injuries or property damage below. However, controlled snow shedding is necessary to prevent excessive snow load. The slope of a roof is a major factor in snow sliding; steep slopes (greater than a 3:12 pitch) allow snow to slide more readily, while lower slopes offer more resistance. Metal panels with snow retention devices help control snow shedding, providing a balance between load-bearing and safe dispersal. This is especially important for steep roofs, where snow falling off quickly can lead to hazardous situations, such as damaging external gas lines or creating falling icicles.
3. Ice Dam Prevention
Ice dams are another winter hazard, forming at the roof’s edge when melting snow refreezes. They block drainage, potentially causing structural damage. Ice dams typically form due to air barrier flaws that let warm indoor air escape, melting the snow on the roof’s surface. This melted snow then refreezes at the edges, creating ice barriers that trap more water. Prevention strategies include using peel-and-stick membranes along the roof’s edge, framing with raised heel trusses, and designing roofs without valleys and gutters that are higher than the roofing plane.
4. Installing Snow Retention Systems
Snow retention systems, such as fences, bars, or guards, help manage snow melt safely. These devices slow down snow sliding, allowing it to melt gradually or fall in smaller amounts, reducing the risk of rooftop avalanches. Properly engineered and installed snow retention systems can significantly enhance winter safety by managing snow buildup without compromising the roof’s structural integrity.
5. Protecting Roof Attachments
Snow sliding down a roof can dislodge or damage attachments like exhaust vents. These attachments should be installed as high on the slope as possible to minimize their exposure to sliding snow. Alternatively, protective snow retention systems can safeguard these attachments by controlling the flow of snow across the roof.
6. Proper Snow Removal Techniques
Excess snow buildup can lead to hazardous load levels, so snow removal after heavy storms is critical. However, it’s essential to remove snow with care to avoid damaging the roof surface. Using metal or sharp tools could scratch or dent the metal panels, potentially causing rust or leaks. Experts recommend leaving a thin layer of snow on the roof to melt naturally, only removing the excess, and doing so uniformly across the surface. This method prevents unbalanced weight and avoids roof damage during removal.
7. Additional Considerations for Metal Roofs in Snowy Conditions
Roof Material and Surface Color
Metal roofs can absorb and radiate heat efficiently, which can help prevent snow from accumulating. Darker roof colors, in particular, absorb more solar energy, accelerating snow melting. However, this can sometimes lead to ice dam formation if the roof is not properly sealed and insulated.
Watertightness
For low-sloped roofs, watertight panel seams are crucial to prevent leaks from melting snow. Using panels that have passed ASTM 2140 or FM 4471 Appendix G water tests ensures better water resistance. Water-resistant underlayment is also recommended, regardless of the roof’s slope.
Roof Layout
Certain design elements, like valleys and dormers, can increase snow buildup, leading to unbalanced snow distribution and excessive load in some areas. Drifting snow may also accumulate behind HVAC units, walls, and photovoltaic (PV) panels, so these areas require extra design considerations to maintain balance and safety.
Regular Roof Maintenance
Routine maintenance is essential in heavy snowfall regions. Regular inspections and preventive snow removal help avoid damage to metal panels and maintain roof integrity. Prioritizing these checks, especially after storms, ensures that potential issues are caught early.
Warranty Considerations
If issues arise, consulting with the roofing material manufacturer is essential to maintain warranties. Using unapproved tools or techniques can void warranties, so it’s advisable to review the manufacturer’s guidelines and follow their recommendations.
Conclusion
Metal roofs can provide excellent durability and performance in snowy climates if they are properly designed, maintained, and managed. By understanding the weight of snow loads, installing snow retention systems, preventing ice dams, and conducting regular maintenance, building owners can significantly improve roof safety and longevity. Proactive winter roof care ensures that metal roofs remain a safe, efficient choice for cold regions, providing protection and peace of mind for building occupants and owners alike.