Clear heavy snow off your roof quickly and safely

The forecasters and their predictive models were correct. Your region has been hit by a severe winter storm, with major, perhaps record-setting, snowfall and bone-chilling temperatures and winds. Local businesses, including yours, are temporarily closed to all but essential employees, such as security, facilities and safety personnel. The storm has now passed, and it is time to activate the components of your severe weather Emergency Response Plan (ERP), dedicated to reacting to a severe winter weather event.

During the first 24 hours following a major winter storm, your response will make a critical difference in the pace at which your business can recover and get back into full operation. Both the protection of your property and the safety of your employees are critical to your business resilience.

A weighty emergency

One snowflake is lighter than the smallest feather, but put enough of them together in one place and the impact can be significant. According to a FEMA Snow Load Safety Guide, the weight of one foot of fresh snow ranges from three pounds per square foot for light, dry snow to 21 pounds per square foot for wet, heavy snow. In either case, it does not take long for a commercial roof to be placed under significant stress.

Because of this, it may be prudent to engage the services of a local structural engineer to evaluate the integrity of your building before allowing your personnel on or under the roof. 

Initiating snow removal

Snow removal is not considered safe during an active snowstorm. Once the storm is over and your snow removal plan has been activated, you may begin the process.

Keep in mind that it may not be immediately necessary to remove all snow. Consider:

• Your initial concern should be to clear snow from the most critical areas such as drains, roof edges, drift areas and centers of bays.
• Clear snow close to, but not down to, the roof surface. Removing snow down to the roof surface can result in unintended damage. Some guidelines recommend leaving at least two inches of snow as a buffer.

Don’t shovel the same snow twice

One important recommendation is not to move snow more than once. In other words, when a shovel-full of snow has been lifted, place it in a sled, tub or hopper to transport it off the roof. Shoveling snow from one part of your roof and dropping it in another can lead to increased volume of water due to snow melting, snow compaction resulting in increased weight on that section of the roof, and the potential for damage if compacted snow must be shoveled again.

Additional snow reduction steps

Beyond the straightforward process of snow removal, there are a number of other actions businesses can take in the aftermath of a major snowstorm that can contribute to an effective response, including:

Increase building heat

Because most roof assemblies allow some heat transfer from inside the building to the underside of the roof deck, increasing the internal temperature of your facility may promote roof snow melt. 

Keep in mind that suspended ceilings beneath the main roof deck may prevent an increased internal temperature from having the desired effect on overhead snow accumulation. The temporary removal of some ceiling tiles can help warm the underside of the roof deck and promote snow melt.

Clear drains

Clear all drain inlets and outlets to allow for better drainage of water from melting snow. Clogged drains can lead to ice accumulation, and ice accumulation can contribute to roof failures during later snow or rain events.

Periodically recheck drains to verify they remain clear, especially when ambient temperatures may cause ice dams and blockages. Remove snow in an area approximately 10 feet around drains and along roof perimeters. External gutters and downspouts can quickly become obstructed by snow that melts and then refreezes before the water can flow out of the downspouts. So, early in a snow event, clear downspout outlets of ground snow accumulations. This includes any snow pushed near downspout outlets as parking lots and sidewalks are cleared.

Combat snow drifts

Deeper snow drifts take longer to melt and drain from a roof, so target any such formations early in the snow removal process. Their presence over a longer period can increase the likelihood that another snow or rain event may add to the snow load in areas where drifting has accumulated.

Balance snow loads during removal

Keep in mind the strongest sections of the roof are above the column lines supporting the roof, meaning that the areas above column lines should be the last areas cleared. This is important because snow forms a relatively even load across a roof. Snow should be removed in a balanced manner. For example, as snow is removed from the center of a bay on one side of a peaked roof, the next action should be to remove the snow from the corresponding center of bay on the other side of the peak. 

When clearing snow from a peaked roof, clear from the eave towards the peak. This promotes the flow of water to drains.

As snow is removed, beware of obstacles that may be hidden beneath the snow. Roofs may have exposed equipment, piping, wiring and lightning protection that may be hidden beneath the snow. Some roofs may also have skylights or other features that introduce fall hazards. Prior to snow season, prepare maps showing the locations of these features so workers are aware of their presence. Also, mark the locations of these features by installing flags, markers or other delineators tall enough to extend above the level of the snow.

Avoid using tarps

Avoid tarps used to collect, lift and remove snow by crane. While the load of snow on a tarp may be a simple task for a crane, it could temporarily overload the roof deck while supporting a snow-laden tarp.

Contracting snow removal services

If your business does not have personnel on staff with the experience to safely remove snow from your roof, secure the services of a qualified contactor to implement snow removal following a safe work plan. 

Review detailed safety rules and regulations with all contractors and obtain contractor signatures indicating they have received this training. 

And always ask contractors to provide Certificates of Insurance verifying adequate coverages for Workers’ Compensation and General Liability. Also verify that coverage is provided for property damage or bodily injuries caused by contractor's employees or their operations.

Visit the Winter Storm Resource Hub for additional insights.