Commercial Roof Snow Removal: What Chicago Building Owners Need to Know

Chicago winters are unforgiving. Between November and March, the city regularly sees heavy snowfall, freezing rain, and rapid temperature swings that can pile massive weight onto commercial flat roofs. For building owners and facility managers, understanding when and how to remove that snow is not just a maintenance concern - it is a structural safety issue that can prevent catastrophic roof collapse, costly water damage, and business interruption.

At Windward Roofing & Construction, we have provided commercial roof snow removal services throughout the Chicago metropolitan area for over 40 years. We have seen firsthand what happens when buildings go unmonitored during major storms, and we have helped countless property owners develop proactive plans that keep their roofs safe throughout the winter season. This guide shares what we have learned so you can protect your building and your investment.

Why Snow on a Commercial Roof Is Dangerous

Snow may look light and fluffy when it first falls, but it is deceptively heavy, and the weight can accumulate rapidly during sustained storms. A single cubic foot of fresh, dry snow weighs roughly 3 to 5 pounds. Wet, packed snow can weigh 15 to 20 pounds per cubic foot, and ice weighs approximately 57 pounds per cubic foot. When you consider that a typical commercial flat roof can span tens of thousands of square feet, the total load becomes enormous.

The danger is compounded on flat roofs because water from melting snow has nowhere to go if drains are blocked. As snow accumulates and melts partially during the day, refreezing at night creates layers of ice mixed with snow. This dense, layered accumulation can approach the weight of solid ice far more quickly than most building owners realize.

Roof collapses caused by snow overloading are not rare in the Midwest. Large-span buildings such as warehouses, manufacturing facilities, retail centers, and arenas are particularly vulnerable because their long structural spans concentrate loads in ways that smaller buildings do not. Even when a full collapse does not occur, excessive snow loads can cause permanent structural deflection, membrane damage, and interior water intrusion that leads to expensive repairs and insurance claims.

Understanding Your Roof's Load Capacity

Every commercial building is designed to handle a specific amount of live load, which includes snow, rain, maintenance workers, and rooftop equipment. In Chicago and the surrounding suburbs, the building code ground snow load is 25 pounds per square foot, and the actual design load for your roof will depend on building type, age, and structural system.

However, the design load represents the maximum the structure is engineered to support, not the amount of weight you should allow to accumulate before taking action. Most structural engineers recommend initiating snow removal when loads reach 50 to 60 percent of the design capacity, leaving a safety margin for unexpected additional precipitation or drifting.

Key factors that affect your roof's vulnerability:

• Roof span and structural system. Long-span steel bar joists, wood trusses, and pre-engineered metal buildings are more susceptible to snow overload than short-span concrete structures.
• Building age and condition. Older buildings may have experienced structural degradation, corrosion, or modifications that reduce their original load capacity.
• Drifting patterns. Parapet walls, rooftop equipment, and adjacent taller buildings create wind shadow zones where snow drifts can pile to double or triple the depth of the surrounding roof area.
• Drainage conditions. Blocked or slow drains hold meltwater on the roof, adding significant weight beyond the snow itself.
• Insulation and heat loss. Buildings that lose heat through the roof may experience complex melt-freeze cycles that create heavy ice layers beneath the snow pack.

When to Remove Snow from Your Commercial Roof

The decision to remove snow should be based on measured conditions, not guesswork. Here are the general thresholds that should prompt action:

Immediate removal is recommended when:

• Snow accumulation reaches 12 inches or more of heavy, wet snow
• Snow accumulation reaches 24 inches or more of lighter, dry snow
• Visible drifting has created localized accumulations of 3 feet or more near parapets, equipment curbs, or elevation changes
• Rain is falling on top of an existing snow pack, dramatically increasing its weight
• Interior signs of structural stress appear, including unusual sounds (popping, creaking), visible deflection in ceiling or structure, doors or windows that suddenly become difficult to open, or new cracks in walls or ceilings

Proactive monitoring should begin when:

• Any measurable snow accumulation is present and additional storms are forecast
• Temperatures remain below freezing for extended periods, preventing natural melt-off
• Freeze-thaw cycles are creating ice layers within the snow pack
• Roof drains are partially or fully blocked by ice or debris

If you are ever uncertain whether your roof can handle the current snow load, err on the side of caution and contact a professional. The cost of an unnecessary service call is negligible compared to the cost of a structural failure.

Safe Snow Removal Procedures

Commercial roof snow removal is inherently dangerous work. It takes place at height, on slippery surfaces, often in poor visibility and extreme cold. It also carries the risk of damaging the roofing membrane if done improperly. For these reasons, snow removal should always be performed by trained, equipped professionals.

Proper snow removal practices include:

1. Balanced removal patterns. Snow should never be removed from only one side of the roof or one section at a time, because doing so creates unbalanced loads that can be more dangerous than the evenly distributed snow. Professional crews work in systematic patterns to reduce weight evenly across the entire roof area.

2. Leave a protective layer. Crews should leave 1 to 2 inches of snow on the membrane surface rather than scraping down to the bare roof. Shovels, scrapers, and power equipment can gouge, puncture, or tear roofing membranes, and damage done during winter removal may not become apparent until spring thaw reveals new leaks.

3. Use the right tools. Plastic shovels, snow rakes, and rubber-edged pushers are appropriate for membrane roofs. Metal shovels, ice picks, and snow blowers with metal augers can destroy roofing materials. The choice of equipment should be matched to the specific roofing system installed.

4. Protect roof penetrations. Drains, vents, pipes, HVAC curbs, and skylights must be identified and protected during removal. Striking these components with snow removal equipment can create leaks and cause expensive damage to both the roofing system and the equipment itself.

5. Fall protection. All workers on the roof must use fall protection equipment in compliance with OSHA requirements. This includes harnesses, lanyards, anchor points, and perimeter warning lines. A commercial roof covered in snow and ice is one of the most hazardous work environments in the construction industry.

6. Monitor during removal. As snow is removed, the structural load shifts. Crews should monitor the building for signs of distress during the removal process and be prepared to evacuate if the structure shows any signs of instability.

Prevention: Reducing Snow and Ice Problems Before They Start

The best snow removal strategy is one that minimizes the need for emergency intervention. Proactive steps taken before and during winter can significantly reduce your risk.

Fall roof inspection and maintenance. Schedule a comprehensive roof maintenance visit before the first snowfall. Clear all drains, scuppers, and gutters of debris. Inspect and repair flashing, sealants, and membrane seams. Confirm that all roof access hatches and safety equipment are in good working order. Address any areas of ponding water that could freeze and create heavy ice accumulations.

Drainage system maintenance. Roof drains are your primary defense against standing water and ice buildup. Drains that are clogged with leaves, debris, or sediment will trap meltwater on the roof, adding weight and creating ice dams. Install drain guards or heat trace cables on interior drains to keep them flowing during freezing weather.

Insulation assessment. Buildings with poor roof insulation lose heat through the roof surface, causing uneven melting that refreezes at cold spots and edges. Upgrading insulation improves energy efficiency year-round and reduces the formation of ice dams and the complex snow-ice layering that creates the heaviest roof loads.

Establish a snow removal plan. Do not wait until a blizzard hits to figure out who to call. Establish a relationship with a qualified roofing contractor who provides snow removal services, and arrange a seasonal contract that guarantees response times and priority service. Know your roof's load limits, and establish clear trigger points for when removal crews should be dispatched.

Document your roof's structural capacity. If you do not already have your building's structural drawings, obtain them. Your structural engineer can help you establish specific load thresholds and develop a monitoring protocol. This information is also essential for communicating with your snow removal contractor and your insurance provider.

Ice Dams and Their Impact on Commercial Roofs

Ice dams form when heat escaping through the roof melts snow on the upper sections, and the meltwater refreezes at the colder roof edges, parapets, or drain locations. The resulting ice barrier traps additional meltwater behind it, which can back up under flashings and membrane laps, infiltrating the building interior.

On commercial flat roofs, ice dams most commonly form around interior roof drains, at parapet wall junctions, and near HVAC equipment curbs. The standing water trapped behind these ice formations adds tremendous weight to the roof while simultaneously creating conditions for leaks.

Preventing ice dams requires a combination of adequate insulation, proper air sealing to minimize heat loss through the roof deck, and functional drainage that keeps water moving off the roof before it can freeze. Heat trace cables installed along drain leaders and at vulnerable edge conditions can also help maintain drainage flow during extended cold periods.

Choosing a Snow Removal Contractor

Not all snow removal companies are qualified to work on commercial roofs. Ground-level snow plowing and parking lot clearing require very different skills and equipment than rooftop operations. When selecting a contractor for commercial roof snow removal, verify the following:

• Roofing expertise. The contractor should be a licensed commercial roofing company that understands membrane systems, structural considerations, and where sensitive components are located on the roof.
• Safety program. Ask about their fall protection equipment, safety training, and OSHA compliance. Workers on snow-covered roofs face extreme fall hazards, and the contractor must have a robust safety program.
• Insurance coverage. Verify that the contractor carries adequate general liability and workers' compensation insurance. If an uninsured worker falls or if the contractor damages your roof, you could be liable.
• Response time. During major storms, every roofing contractor in the region is overwhelmed with calls. A pre-arranged seasonal contract with guaranteed response windows ensures your building will not be at the bottom of the list.
• Equipment appropriate for your roof type. The contractor should confirm they will use tools and methods suitable for your specific roofing membrane. Ask what equipment they use and confirm that metal tools and heavy machinery will not be dragged across your roof surface.

Emergency Situations: When to Evacuate

In rare but critical situations, the safest response to an overloaded roof is not snow removal but building evacuation. If you observe any of the following conditions, evacuate the building immediately and call both emergency services and your roofing contractor:

• Visible sagging or deflection of the roof deck or structural members
• Loud cracking, popping, or groaning sounds from the roof structure
• Doors or windows that suddenly bind or will not close properly
• New cracks appearing in interior walls, especially near the ceiling
• Sprinkler heads that have dropped below the ceiling level
• Water infiltration appearing at multiple locations simultaneously

These signs indicate the structure is under severe stress and could be approaching its failure point. Do not send anyone onto the roof to remove snow until a structural engineer has assessed the building. Windward Roofing provides 24/7 emergency roofing services and can coordinate with structural engineers to develop a safe remediation plan for overloaded roofs.

Protect Your Building This Winter

Snow management is an essential part of owning a commercial building in the Chicago area. The combination of heavy lake-effect snowfall, sustained freezing temperatures, and the large flat roofs typical of commercial construction creates conditions that demand attention and preparation.

By understanding your roof's load capacity, maintaining your drainage systems, establishing a relationship with a qualified snow removal contractor, and knowing when to take action, you can protect your building, your tenants, and your investment throughout even the most severe Midwest winters.

Windward Roofing & Construction provides commercial roof snow removal, winter emergency services, and preventive maintenance programs for building owners throughout Chicago and the surrounding suburbs. Contact us to discuss a seasonal snow management plan for your property, or call our 24/7 emergency line at (844) 880-8844 when you need immediate assistance.

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