Warnings, vigilance follow increase in roof collapses

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By Milton J. Valencia
Globe Staff / February 4, 2011

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A series of life-endangering roof collapses throughout the state — and the threat of another storm this weekend — is prompting public safety officials to ratchet up warnings about structural safety and the need to take precautions, such as having snow removed from roofs, particularly if they are flat.

“Following several days of snow and freezing rain, the dangers of roof collapse are real,’’ Governor Deval Patrick said yesterday as he announced he would seek federal assistance. “I am urging homeowners, business owners, and public officials across the state to be extra vigilant for their own safety, and for the structural integrities of their homes and businesses.’’

More than 70 buildings, mostly flat-roofed commercial structures, have had their roofs partially or completely collapse under snow and ice accumulation, or have been evacuated because of concerns over structural damage, said Peter Judge, spokesman for the Massachusetts Emergency Management Agency.

He called the number of collapses “mind-boggling.’’

Patrick asked the Massachusetts Emergency Management Agency late yesterday afternoon to seek eligibility for a federal physical disaster declaration or economic injury declaration, which would make the state and property owners eligible for repair reimbursements.

Students were evacuated from the Perley Elementary School in Georgetown yesterday after a partial roof collapse, and 20 people were forced from a commercial condominium building in Weymouth after a partial roof collapse. The Lincoln Mall remained closed yesterday after part of the roof of a grocery market inside collapsed Wednesday night.

And in Chelsea, an elderly woman was taken out of her home by emergency personnel yesterday morning after the roof of a converted auto body garage caved in next door, pushing in a portion of one wall of her house and sending plates flying out of her kitchen cabinets. She was shaken but OK, said her grandson.

“It’s not like we are going to have a nice melt over the next couple of days,’’ Judge said. “I would hope that anyone who owns or manages a big, flat-roofed building has had someone up on the roof removing snow.’’

Officials urged anyone who suspects any problems may be developing to call 911 and evacuate immediately. Such quick action may have saved dozens of people who fled a building in Easton within minutes of its collapse Wednesday, officials said.

While dozens of people have been put in potentially dangerous situations, fortunately no one has been seriously hurt, Judge said.

Many of the buildings that have had roofs collapse, particularly the commercial and industrial structures, are believed to have been built before code regulations were enacted following a series of roof collapses when the Blizzard of 1978 hit, said Jim Russo, president of Russo Bar Associates Inc., a Burlington engineering firm that designs and builds roofs.

He said new buildings are designed to handle heavy snowfall, but the recent mix of snow and sleet is putting extraordinary pressure on structures.

According to modern state building code regulations, for instance, a flat roof must be able to support a snow load of 31.5 pounds per square foot, and according to engineering and meteorologist studies, Russo said, the average density of a snowfall is 6 pounds per cubic foot.

That means it would take 5 feet of snow to put a roof in danger of collapse.

But, given the mixture of ice, sleet and rain the area has experienced recently, the weight of a cubic foot of snow could be considerably more — as much as 13 to 15 pounds — leaving roofs vulnerable to the heavy pressure.

A building that collapsed in Revere last week, before the Tuesday and Wednesday storms, already had about 3 feet of packed snow, the city’s fire chief said.

Donald O. Dusenberry, senior principal at structural engineering firm Simpson, Gumpertz and Heger, Inc., said that roofs — including flat roofs — can be designed to handle heavy snowfall. Those that are outdated can easily be retrofitted to drain better or reduce wind drifts, the typical reason for a large accumulation of snow in one area.

The main reason for the collapses is that property owners and managers don’t clear snow and slush from roofs or ice from gutters, particularly, he said, after heavy accumulation during recent storms.

“What’s happening is we’re getting a substantial buildup of snow on these roofs, snow after snow,’’ he said, “and 20 inches of snow that accumulates after a series of storms is a lot heavier than 20 inches of snow that falls in one storm. It’s a particular problem if you’ve got rain on top of that snow.’’

Temperatures today are expected to reach into the low 30s, with sunny skies. But conditions could worsen this weekend, with the National Weather Service in Taunton predicting possible snowfall tomorrow bringing a messy mix of rain beginning just before noon and snow through the evening.

Some inland areas could see as much as 6 inches, said Neal Strauss, a meteorologist with the weather service. Strauss said the mostly wet snowfall will add to the pressure already mounting on rooftops.

“It won’t take too much more to cause additional structural issues for buildings that already have a lot of snow accumulation on them already,’’ Strauss said. “Obviously, it’s a concern.’’

The wet snowfall will cause some street flooding but should not pose a serious threat.

As of 6 a.m. yesterday, the weather service reported 70.5 inches of snow has fallen this season at Logan International Airport, compared with the average season snowfall of 41.8 inches.

Terrel Harris, spokesman for the state Executive Office of Public Safety, said yesterday that this winter season has been unusual in creating this type of pressure of structures.

“We haven’t seen sustained snow accumulation like we are now,’’ he said.

But at the same time, state public safety officials already have been working to increase the required snow support limit for roofs as part of a clean energy program.

Because green energy buildings would emit less heat, they would be less likely to melt snow accumulated on roofs, so the increased weight requirement would be mandated, Harris said.

“The newer codes are going to raise the standards for roofs,’’ he said.

The collapses occurred mostly in commercial buildings but also in a number of homes.

The roof of a house under renovation in Jamaica Plain collapsed yesterday morning, forcing the evacuation of an adjacent home.

In Reading, a homeowner and his son saw the walls of their house crumbling and escaped before their roof caved in.

Officials took extreme precautionary measures yesterday in school buildings. Besides the Georgetown school, the South Shore Charter School in Norwell had to be evacuated because of the roof’s condition, Chief Andy Reardon said.

All 11 public schools in Peabody were closed yesterday as a precautionary measure, Peabody Superintendent Milton Burnett said.

“There were no structural compromises; it was completely precautionary,’’ he said.

Martin Finucane of the Globe staff and Globe correspondents Jenna Duncan and Katherine Landergan contributed to this report.