What to Do During a Significant Snow Event
Post date: Jan 21, 2016 3:07:12 PM
FEMA recommendations for roof systems during winter weather:
What to Do During a Significant Snow Event
Your Snow Event Response Plan should be reviewed. The Plan should define a methodology to determine an approximate snow load and at what point snow removal should be initiated. Snow removal will prevent overstressing of the roof structure. Having an in-house plan for snow removal in place or a contractor on retainer is imperative. Contractors will be in high demand and difficult to find once a snow storm begins.
What to Do After a Major Snow Event
Even if snow accumulation during an individual snow event approaches but does not surpass the threshold of safety, removal of snow from the roof may still be in order. Roof snow that is exposed to sunlight can soften, become denser, and then harden when the temperature drops below freezing. Melting water may pool and subsequently freeze, creating a concentrated area of loading on the roof. If subsequent snow events are anticipated, removing snow from the roof will minimize the risk of accumulating snow causing structural damage. One benefit of immediate snow removal is that the effort required to remove the snow from the rooftop is reduced. However, when snow accumulation is minor, the likelihood of damaging the roofing material or risk of being on a roof outweighs the benefits of removal.
WARNING
If there is any concern that snow loads may cause a collapse of the roof structure, cease all removal activity and evacuate the building.
Safety Measures for Snow Removal
Any roof snow removal should be conducted following proper OSHA protocol for work on rooftops. Use roof fall arrest harnesses where applicable. Always have someone below the roof to keep foot traffic away from locations where falling snow or ice could cause injuries.
MEASURES TO REDUCE THE POTENTIAL OF SNOW LOAD-INDUCED STRUCTURAL FAILURES
Ensure someone confirms that the area below removal site is free of equipment that could be damaged by falling snow or ice.
Whenever snow is being removed from a roof, be careful of dislodged icicles. An icicle falling from a short height can still cause damage or injury.
When using a non-metallic snow rake, be aware that roof snow can slide at any moment. Keep a safe distance away from the eave to remain outside of the sliding range.
Buried skylights pose a high risk to workers on a roof removing snow. Properly mark this hazard as well as other rooftop hazards prior to snow events.
Method of Snow Removal
Removing snow completely from a roof surface can result in serious damage to the roof covering and possibly lead to leaks and additional damage. At least 2 inches of snow should be left on the roof.
Do not use mechanical snow removal equipment. The risk of damaging the roof membrane or other rooftop items outweighs the advantage of speed.
Do not use sharp tools, such as picks, to remove snow. Use plastic rather than metal shovels.
Remove drifted snow first at building elevation changes, parapets, and around equipment.
Once drifted snow has been removed, start remaining snow removal from the center portion of the roof.
Remove snow in the direction of primary structural members. This will prevent unbalanced snow loading.
Do not stockpile snow on the roof.
Dispose of removed snow in designated areas on the ground.
Keep snow away from building exits, fire escapes, drain downspouts, ventilation openings, and equipment.
If possible, remove snow starting at the ridge and moving toward the eave for gable and sloped roofs.
Use a non-metallic snow rake for steep roof slopes if possible. Metal snow rakes can damage roofing material and should be avoided. Snow removal can be conducted from the ground, removing the risk to people on a hazardous roof.
Upon completion of snow removal, the roofing material should be inspected for any signs of damage. Additionally, a quick inspection of the structural system may be prudent after particularly large snow events.