Heed signs of too much snow on roof

Officials are advising people to pay close attention to signs that the roofs of buildings may be stressed from recent snowfall.

State Fire Marshal Bill Degnan issued a statement Wednesday saying that because of "recent successive snowstorms, there is a greater urgency to clear roofs of snow and ice that has accumulated."

Warning signs range from the subtle, such as doors that pop open, to the obvious, such as leaking ceilings, which could indicate a simple repair is needed or collapse could occur.

"High roof parapets can accumulate drifting snow, and unbalanced loads due to the recent high winds add even more strain to roof structures," Degnan said.

William McKinney, manager of Nashua’s Building Safety Department, said Wednesday it’s time to "pay attention."

"I’m not overly concerned at this point," said McKinney, who said recent storms "didn’t produce the amount we were anticipating.

"There is definitely more concern in the Northern and Eastern part of the state along the Maine border, as they received substantially more snow in the last storm," he said, but noted it’s time to start monitoring roof loads to combat weight problems as well as to prevent ice dams.

Dan Donovan, chief operating officer for the Nashua School system, said his department "has an eye on things" but is not removing what snow there is from the top of the city’s 17 schools.

The Epping Elementary School was closed Wednesday so crews could remove snow. The town’s middle and high school will be closed for the same reason Thursday.

Donovan said the district’s director of plant operations, Shawn Smith, "has a report to let us know how much snow each roof can handle." Donovan said he has asked each of the school’s principals to "take a look and see how everything is. Luckily most of the snow is on the light side."

The Federal Emergency Management Administration report on snow load management says roof snow that is exposed to sunlight can soften, become denser and harden when the temperature drops below freezing.

"It’s that time of year," McKinney said. "The sun is quite strong, and there is more daylight that actually causes warming of the roof. When snow melts and hits cold, it freezes and starts to back up water."

FEMA says that pooled and refrozen water can form a concentrated area of weight on a roof.

"If subsequent snow events are anticipated, removing snow from the roof will minimize the risk of accumulating snow causing structural damage," FEMA says.

"Hire a professional or get a roof rake," Hudson Deputy Fire Chief John O’Brien said. "Don’t go up on the roof. Unsafe attempts at doing the work yourself could be tragic. We’ve seen it."

O’Brien said people should also "try to identify why they’re getting ice dams." The cause could be "lack of venting or insulation; it can be many different things," he said. "Try to identify the problem so you don’t get it next year."

Maintaining the integrity of the roof itself is also important. Damage can occur when aggressive removal methods are used. Mechanical devices and sharp tools are to be avoided. Snow shouldn’t be piled near building exits or along walkways.

"Past fire investigations have determined that fuel-gas service to some buildings have been damaged due to heavy snow loads and snow sliding off roofs onto gas meters and components," Degnan said in his advisory. "In addition, snow sliding off roofs onto outside oil tanks has caused valves and filters to be broken off."

Don Himsel can be reached at 594-1249, dhimsel@nashuatelegraph.com or @Telegraph_DonH.