Snow Loading: Managing the Risks

Every year snow loading takes a toll on businesses, homes, and public facilities in northern regions. Most businesses and homeowners start preparation for snowfalls before winter approaches by creating snow removal plans for sidewalks, parking lots, and roadways, contracting snowplows, and winterizing vehicles. Yet making a plan for snow removal to prevent a roof collapse may be the most critical.

When a record storm occurs, or when a unique combination of moderate snowfall and thawing repeats, structures can be challenged to their design limits. When collapses occur, they are sudden and often catastrophic, very costly in terms of property damage, and can interrupt production and operations.

With repeated stresses and strains, “building to code” is often not a reliable defense against damage or collapse from snow loading. Roof additions, changes to roof-mounted equipment, and sustainability upgrades (i.e., “green roofs”) can lead to additional snow accumulation and drifting. Further, joists and structural members installed at original construction may have been rendered insufficient by added interior loads (such as large fans or increased lighting), age, and wear and tear. The thousands of welds in open bar steel joists may not have been thoroughly inspected during construction and hidden defect(s) never identified.

Heavy, repeated snowfall and subsequent melting between storms creates a freeze–thaw cycle that can cause roof overloading. Sloped roofs are subject to ice dams and water penetration to interiors; and once such a flow begins, it only ends when the snow is melted off the roof. Flat or low pitch roofs are subject to bellowing, which exacerbates the condition, followed by further deflection, further accumulation, and can lead to collapses.

“Snow Loading: Managing the Risks” can help you rein in snow-load risks this winter. It covers:

• How to identify common problem areas and steps to remediate them.
• Actions to take before, during, and after a snowstorm that causes major accumulation.
• Best practices and risk mitigation strategies.
• Public information sources.