News

Dam, that ice!
How to prevent ice dams, spring's dangerous intruder
By Elizabeth Prata

Imagine sitting in your living room on a mild March day, hearing the sound of gently trickling water. Thinking it is just the icicles melting and what a nice a nice spring-like sound, you grow concerned when you hear it getting louder, and suddenly feel the tell-tale drip on your arm as you raise your cup of coffee to your lips.

An ice dam has built up on your roof and now water has penetrated the shingles, roof, and walls.

During a major storm, the focus is on the snow, plowing the snow, driving in the snow, removing the snow. Gray Public Works Director Steve LaVallee said in his eleven years of overseeing winter operations, that this winter had not been so unusual in the amount of snow received but is has been unusual in the severity and the closeness of the storms.

Right, this roof line has at least a half a foot of ice lining the edge, and a two foot thick diameter icicle at the end of the gutter, preventing water from both running down the gutter and off the roof. These homeowners should watch out for ice dam build up. The Monument: Prata photo

Four feet of snow in one week

"It can stop anytime!" Mr. LaVallee said. "It's been a hard winter, but the boys faced up well and the equipment held up well too." Mr. LaVallee noted that this week the Town of Gray received 4 feet of snow between Tuesday evening and the last flake that fell early Sunday morning. "Now, that's unusual. I can't ever remember such a stretch when we got this much all at once."

The National Oceanographic and Atmospheric Administration (NOAA) Weather Service Forecast Office put this year's storms in perspective. The service has been keeping snowfall records in Gray since the 1995. So far this year there has been 106.1 inches of snow in Gray which makes it the third snowiest season. Still outranking this year's totals are 1995-1996 at 130.6 inches and 2000-2001 at 127.6 inches.

	Joel and Nate Bruns at Bruns Brothers in Gray shoveling the roof of the plant. They are appropriately equipped for this dangerous job. They each wear a harness with a tether that attaches them to the roof. The tether is no longer than the roof, so if they slip, they will not slide completely off.
"We don't want them dangling there," The Monument was told. The tether has an elastic jump line to allow for spring if they do slip and slide. Finally, they do not shovel all the way to the edge yet, allowing for that bit of snow lining the edge to provide additional buffer before clearing it off completely.
	The doors on the side of the building the men are working will be locked. That's to avoid an unpleasant surprise of a load of snow dumped on the neck of an unsuspecting employee who leaves at just the wrong moment. Also, the snow that's removed makes quite a mess on the ground below, so the Bobcat is put into good use and all that shoveled snow will be trucked away. Why were they shoveling the roof? To avoid an ice dam. The Monument: Prata photos

Official weather tallies

Jim Mansfield at the NOAA office said that there is still time in the season for those records to be broken. He pointed out that the record 2000-2001 season received a whopping 58.3 inches in March alone, making up nearly half of the whole season's record amount. Last season's snowfall amounts were the lowest of the last ten years with only 53.4 inches of snow.

Mansfield said that in order to get a true idea of climactic normals for the area the service would need data for thirty years instead of just ten. Taking that in to consideration, the average season snowfall amount for this area is 82.07 inches. That could rise slightly if there is additional snow this year.

SAD 15 and the Middle School roof

George Litrocapes from MSAD 15 reports no problems with snow loads on the schools this year, citing the fact that the previous storms all had significant wind that blew the snow off the roofs. This last storm was the only one that had wet snow that didn't get blown off and he estimates that there is only 8 inches up there now. He said that there are only minimal problems with ice at the Middle School because electric heat was installed on the roof last year. The heat keeps troughs open in the valleys so that when the ice melts the water can drain off the roof.

The Middle School has a metal roof that is causing some maintenance problems. As the snow melts it slides down and blocks the unit ventilators. With each storm the problem can worsen. Litrocapes noted that they have been going around and clearing the snow from the ventilation units and are in the process of clearing all the windows that are snow covered as well.

As the crews plow and then spend time sweeping snow back, clearing sidewalks, and trucking snow away, the snow remains on your roof.

At the roof's edge, icicles build up and now a ridge of ice lines the roof all the way around. The snow on the roof above will melt more quickly than the thick ice ridge, and it's heavy, too. The time is ripe for an ice dam.

Wet snow: A heavy load

New Gloucester Code Enforcement Office Debby Parks said that roof loads are calculated by code to be able to take the stresses of average amounts of snow and ice. The national building code has regional differences in their engineering standards. Maine is divided into two regions for the purposes of calculating snow loads the northern region and the southern. Houses built to code in southern Maine are required to be able to take 40 pounds per square foot of live load and 10 pounds of dead load, said Ms. Parks. Dead load is the weight of the actual roof structure.

Roofs that have more of an overhand, and are away from the radiant heat of the walls within the home, are more prone to have potential for ice dam buildup. Below are excerpts from the UMaine Cooperative Extension Service fact sheet on ice dams, reprinted with permission.

What is an ice Dam?

An ice dam is a ridge of ice that forms at the lower edge of a roof and prevents water produced by melting snow from draining off the roof. The water that backs up behind the dam can leak into a building and cause damage to walls, ceilings, insulation, and other areas.

Ice dams occur when the snow on a roof surface that is above 32 degrees F will melt. As water flows down the roof, it reaches the portion of the roof that is below 32 degrees F and freezes. This creates an ice dam.

This water finds cracks and openings in the exterior roof covering and flows into the attic space. In the most common case, the water simply backs up and flows under the shingles. From the attic, it could move into exterior walls or through the ceiling insulation and stain the ceiling finish.

Dealing with and preventing ice Dams

Ice dams can be prevented by controlling heat loss from the home.

Immediate actions:
Remove snow from the roof. A "roof rake" and push broom can be used to remove snow, but may damage the roofing materials. (Note: Make sure you take safety precautions if you do this yourself. Or hire a professional.)

In an emergency situation, where water is flowing into the house, make channels through the ice dam to allow the water behind the dam to drain off the roof. Hosing with tap water on a warm day will help.

Work upward from the lower edge of the dam. The channel will become ineffective within days and is only a temporary solution to ice dam damage.

Mold, mildew and air quality

Moisture entering the home from ice dams can lead to the growth of mold and mildew. These can cause respiratory problems. It is important that the growth of mold and mildew be prevented. Dry out portions of the house that are wet or damp.

Source: "Ice Dams," by T. Larson, L. Hendricks and P. Huelman, University of Minnesota Extension Service, 1997. Reviewed by Jim Philp, UMCE forestry specialist. Reprinted by UMaine Cooperative Extension.

For more information on emergency preparedness, contact your county Extension office.