Snow/Ice Accumulation Leads to a Roof Collapse

Author

Allan_Abbata_WEB

Expertise Includes:

    • Building Foundation Issues
    • Civil/Site Work Evaluation
    • Concrete Systems - Cracks/Settlements/Failures
    • Construction Defects/Claims
    • Storm Water Control
    • Structural Design - Collapse/Failure Analysis

During the next several months when temperatures start to fall below the freezing point and winter storms packing cold temperatures, heavy snowfall and ice build-ups bear down on various regions of the country, they can and do bring an assortment of unfavorable conditions that could and will affect your insured’s buildings, businesses, and personnel. Some of these regions have already experienced record-breaking snowfalls and bitter cold temperatures, which in turn have increased the danger of roof or partial roof collapses. Roofs that are properly designed and constructed to applicable codes and standards should be built to withstand loading from snow, drifting snow, water-laden snow and ice build-ups. But are they? Building codes and standards that depict the proper roof loads will vary across the U.S.  They will generally be based on local historical data, including the expected frequency and intensity of these winter storms in a particular region as shown and discussed in ASCE 7-10.

An overhead view of a building that lost its roof due to the weight of several inches of snow.

There are several questions an adjuster should ask when investigating a roof collapse:

  • What were the specific circumstances (weather event) leading to the collapsed roof?
  • What loading criteria and code year were used to design the roof system?
  • Did the roof system as designed meet the required loading criteria?
  • Were there any new building additions constructed with varying roof slopes and elevations?
  • Were there signs of drifting snow areas which increase the loading to the roof structure?
  • Was a new roof system, a layered reroofing system, or added weight from roof-mounted signs or HVAC equipment installed from what was originally provided?
  • What, if any, improvements may be needed to prevent further or possible future roof collapse?

All of these questions lead to load bearing analyses that can change the roof loading design where allowances that were once anticipated for snow loads may now be compromised. In addition, particular attention should also be given to older structures where past design criteria may have been revised or updated based on code changes or the accumulated local historical data. Special attention should be focused on drifting snow conditions that are extremely dangerous and are most likely the cause attributed to roof collapses. Based on the answers to these questions, an adjuster may now want to consider engaging in the services of a structural engineer to determine the cause or causes of a loss and the feasibility and cost of repair.

A view of a building where the roof collapsed under the weight of 4 to 6 inches of snow.

After a loss such as a roof collapse, it is in the best interests of all parties involved to formulate and develop a plan to consider reviewing any changes, additions or conditions to building(s) that could affect the structural stability of the building’s roof system. Again, a structural engineer can provide this valuable information and more. An additional item to consider in the prevention of a possible roof collapse is an immediate and thorough inspection of the entire roofing system before and after an expected heavy snow and ice event.  These inspections are recommended to visually check and compare all structural framing members and connections, both inside and outside the building. A structural engineer should be called in to perform these inspections and help observe and pinpoint any damage or problems associated with or causing excessive deflection, extreme cracking or deteriorated corrosion. The inspection should also check the roof drains and gutters for debris clogging material where ponded water and/or ice can form and lead to a roof collapse. Also inspect the building walls for verticality and soundness, the windows and doors for proper opening and closing operations and the foundations for heaving and cracking due to frost penetration and settlement from heavy snow and ice loading. After a heavy snow or ice accumulation event and prior to any inspections, develop a plan to safely remove the snow and ice accumulations so that the situation does not further become unsafe.

Allan Abbata  is a senior consulting engineer at Warren and a licensed professional engineer in South Carolina, North Carolina, New York, New Jersey, Pennsylvania, Massachusetts, Missouri, Texas, Alabama, Maryland, Minnesota and Virginia. Allan holds a Bachelor of Science in Civil Engineering. He has more than 40 years of applied engineering expertise to include in-depth knowledge of building codes, rules and regulations that guide design. Allan has also prepared construction drawings and specifications, provided on-site supervision and inspection of construction projects, and. has overseen project management and responsibility for overall performance of building contracts while also serving as the client’s liaison with local, state and federal agencies and municipalities.

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