Snow Loading and Roof Collapse

During winter months, businesses often plan for snow and severe weather by winterizing company vehicles, organizing snowplowing services, etc. However, many neglect to plan appropriately for excess snow loading on roofs, which can cause structural damage or collapse as the weight of snow and ice exceeds the capacity of the roof. The risk of collapse increases when rain falls on accumulated snow, as snow-covered roofs do not drain as well.

Even businesses in warmer climates should be aware of snow loading risks. Facilities in these areas can be more susceptible as they are not designed for winter weather and heavy snow accumulation. Personnel may also not be accustomed to working in these types of conditions.

The following checklist can help you plan, prepare, and take action to minimize the risk of roof damage from snow loading:

  • Determine the maximum safe snow depth for the roof based on its load capacity (indicated in building plans and specifications or in an engineering analysis of the roof design).
  • Inspect the roof structure for damage and deterioration and repair as needed.
  • Inspect roof drains and downspouts, and remove debris to prevent clogging.
  • Look for evidence of past water ponding and eliminate causes such as improperly mounted roof equipment, worn and weathered roof insulation, etc.
  • Identify who is responsible for snow/ice removal and ensure they are trained on appropriate and safe equipment handling and protocols.
  • Locate and appropriately mark skylights, vents, drains, and other items that could be covered by snow so that they are visible to workers.
  • Develop a plan to keep all roof access points clear of snow.
  • Determine what tools, equipment, protective devices, clothing, and footwear are needed to work on a snow-covered roof, and make sure gear is readily available.
  • Confirm any necessary fall protection equipment, such as guardrails, nets, or personal fall-arrest systems, is accessible and installed properly for your building’s roof configuration.
  • Establish a plan to transfer mechanical snow removal equipment to the roof.
  • Prior to using machinery, check with a roofing contractor to ensure equipment will not damage the roof membrane.
  • Require workers to follow manufacturers’ instructions to safely use mechanical equipment and tools, such as shovels, ice spades, and snow blowers.
  • Instruct workers to operate equipment at reduced speeds during slippery conditions, and do not permit the use of powered equipment within 10 feet of any roof edge.
  • Train workers on the proper use of fall-protection equipment and how to identify the warning signs of overexposure and hypothermia.

It’s important to monitor snow depth and be aware of how snow drifts and accumulates. Be sure to:

  • Follow safe roof practices at all times.
  • Remove snow before it reaches 50 percent of the safe maximum depth. Do not allow workers on the roof once the snow load has approached the roof’s load capacity.
  • Remove snow during a storm only if the forecast indicates the total snowfall will result in dangerous accumulations.
  • Do not allow workers on the roof once the snow load approaches the roof’s load capacity.
  • Clear snow and ice from storm drains and catch basins and periodically inspect the roof drainage system to ensure it’s not clogged.
  • Remove snow in layers across the roof to prevent unbalanced loads that may cause a collapse, and avoid making snow piles during the removal process.

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The illustrations, instructions, and principles in this material are general in scope and, to the best of our knowledge, current at the time of publication. No attempt has been made to interpret any referenced codes, standards, or regulations nor to identify all potential risks or requirements.