cityofboston.gov - Official Web Site of the City of Boston - Thomas M. Menino, Mayor

While most commercial and residential roofs are designed to handle loads in excess of what currently exists on rooftops, the current snowpack and potential for additional precipitation does increase the risk of collapses or other structural damage to properties.  While there have been few issues reported in Boston, there have been several reports of roof collapses across the Commonwealth.

Large, flat roofs are at greatest risk, especially those that are not properly draining.  Property owners should be attentive to excessive snow accumulation, ice dams, and poor drainage on rooftops.  For flat roofs with an existing ponding problem; a professional should be called to check the snow load and advise for the snow removal procedure if required. (Ponding is the collection of water which usually indicates a structural problem that can worsen with weight.)

Homeowners and building owners who have concerns about excessive loads and/or the structural integrity of a property, should contact a professional/licensed contractor for assistance. Removing snow from a rooftop can be extremely dangerous, so it is best to rely on professionals.

The Commonwealth has provided helpful tips for safe roof snow removal.

Tips for Homeowners in removing snow and ice from roofs and other areas

DO’s

• Use a snow rake for pitched roofs (available at most hardware stores) to remove snow from your roof. 
• Start from the edge and work your way into the roof.
• Try to shave the snow down to a 2 or 3 inches on the roof instead of scraping the roof clean, which will risk damage to your shingles or other roof covering.
• Keep in mind that any metal tool could conduct electricity if it touches a power line.
• Also, metal tools will do more damage to your roof.
• Shovel snow from flat roofs throwing the snow over the side away from the building.
• Most plastic shovels are better, except for the ones with curved blades—those too will do some damage to your roof.
• Remove large icicles carefully if they're hanging over doorways and walkways.  Consider knocking down icicles through windows using a broom stick.
• Wear protective headgear and goggles when performing any of these tasks.
• Consider hiring professionals to do the job. The combination of heights plus ice makes this one of the more dangerous house chores. 
• If you don't hire professionals, at least have someone outside with you in case anything does go wrong
• Keep gutters, and drains clean, free of ice and snow and keep downspouts clean at ground level.

DON’T’s               

• Unless approved by a registered professional engineer, don’t add your weight or the weight of equipment to the roof.
• Don’t use a ladder since ice tends to build up on both the rungs of the ladder and the soles of your boots.
• Don’t use electric heating devices like hair dryers or heat guns to remove snow and ice.
• Don’t use open-flame devices to remove snow and ice.

According to Meteorologist Tony Petrarca, a cubic foot of dry snow weighs about seven pounds, while a cubic foot of wet snow weighs anywhere from 12 to 18 pounds. So, if it's possible, hire someone to help with all of the snow clearing.
 

 Common Roof Problems

• Sagging roofs 
• Severe roof leaks
• Cracked or split wood members
• Bends or ripples in supports
• Cracks in walls or masonry
• Sheared off screws from steel frames
• Sprinkler heads that have dropped down below ceiling tiles
• Doors that pop open
• Doors or windows that are difficult to open
• Bowed utility pipes or conduit attached at ceiling
• Creaking, cracking or popping sounds

 Other Safety Tips for Homeowners

•  Make sure you smoke alarms and carbon monoxide detectors are working.
• Check your outside fuel and dryer exhaust vents, making sure that they are not obstructed by snow or ice. Never use cooking equipment intended for outside use indoors as a heat source or cooking device. Never use your oven for heat.
• Clear snow away from furnace and dryer exhaust vents to prevent carbon monoxide poisoning.
• Space heaters need space, so use them in a 3-foot circle of safety; free of anything that catch fire. Space heaters are not designed to replace your central heating system; they are only designed to provide a little extra heat on a temporary basis. So be sure to turn them off when you leave room or go to bed at night.
• Clear snow away from downspouts so water has a place to go.
• Do not be tempted to use a heat gun or open flame torch to melt the ice; the risk of starting a fire is huge.
• If you feel you are in immediate danger, get outside and call 9-1-1.

Tips for businesses in removing snow and ice from roofs and other areas

DO’s

• The same tips apply for commercial businesses as homeowners.  However, if you are going to use a snow blower, make sure that it has been approved by a structural engineer to be used on a roof, and that the blower is set to a high level above the roof so as not to damage roof membrane.
• Use a snow rake for pitched roofs (available at most hardware stores) to remove snow from your roof.
• Start from the edge and work your way into the roof.
• Try to shave the snow down to a 2 or 3 inches on the roof instead of scraping the roof clean, which will risk damage to your shingles or other roof covering.
• Keep in mind that any metal tool could conduct electricity if it touches a power line.
• Also, metal tools will do more damage to your roof.
• Shovel snow from flat roofs throwing the snow over the side away from the building.
• Most plastic shovels are better, except for the ones with curved blades—those too will do some damage to your roof.
• Remove large icicles carefully if they're hanging over doorways and walkways.
• Wear protective headgear and goggles when performing any of these tasks.
• Keep gutters, downspouts and drains clean.

 How to Recognize Problems with Roofs in Commercial Buildings

• Sagging roof steel – visually deformed 
• Severe roof leaks
• Cracked or split wood members
• Bends or ripples in metal supports
• Cracks in walls or masonry
• Cracks in welds of steel construction
• Sheared off screws from steel frames 
• Sprinkler heads pushed down below ceiling tiles
• Water puddles where it never has before
• Doors that pop open 
• Doors or windows that are difficult to open
• Bowed utility pipes or conduit attached at ceiling 
•  Creaking, cracking or popping sounds

 What to Do 

• If there is imminent danger, evacuate the building and call 911.