It's that dam time of year again.

Homeowners who spent much of this winter removing snow from their driveways now have to contend with ice dams at their roofs' edge or risk damaging homes due to backups and leaks.

"I feel sorry for some of the people with ice dams. My neighbor's roof? His entryway collapsed," said Joseph Gulso, co-owner of Tree-Mendous Tree Service of Brainerd.

Heat from the home's interior gets into the attic and melts the underside of the snow on the roof, according to the Minnesota Department of Commerce, and the water flows down the roof surface until reaching a cold spot, such as the eaves or soffit, where it forms an ice dam.

Gulso said he knew of a homeowner who had an ice dam that caused substantial damage to her home, not to mention emotional suffering.

"The warming and thawing was causing water to run into her house, and her sheetrock started falling down, and it was a brand-new addition. She was in tears. And I felt bad for her," Gulso said.

Over time, especially with a snow-covered roof in subfreezing temperatures, more ice can build up, and water eventually starts seeping into the home, according to the Commerce Department bulletin.

Ice dams

Tree-Mendous Tree Service offers snow-removal and snowplowing services, including work involving ice dams, which can form with heavy snowfall and extreme cold.

"I've had a lot of calls for roof shoveling due to ice dams. ... I've pretty much put in a hundred hours this last week doing ice dams," Gulso said. "I haven't had much sleep."

If an ice dam is already causing water damage to a home's interior ceilings and walls, the Commerce Department recommends hiring a professional ice dam removal service that uses steamers.

"I recommend trying to clear the whole roof because a lot of times when you roof rake, you create another ice dam right where you're able to reach up to," Gulso said.

A traditional roof rake works by extending the flat end of the rake attached to a pole to reach the roof and pulling the snow on the roof over the eaves or soffits, so the snow falls to the ground.

"You can only reach so far sometimes with those roof rakes, and of the snow you didn't get, it creates another ice dam right where the snow stops," Gulso said.

To prevent ice dams from forming, remove snow from the roof, which can be done using a roof rake, but it may be best to hire a professional snow remover, especially if it involves getting on the roof or using a ladder, which can be a safety risk, according to the Commerce Department.

"What I like to do is clear the whole roof, and I recommend it, but some of the steeper roofs are a challenge, and I end up going up there with a safety harness to clear the roof, so it can be a challenge, and it can be quite expensive," Gulso said.

Ice dams are not caused by roofing, ventilation or gutter problems, as often believed, according to the Minnesota Department of Commerce, but rather from a home that is leaking warm air.

"You can try calcium chloride tablets, and sometimes that will melt channels into the ice dam where it enables the water to flow off rather than getting backed up on the dam," Gulso said.

"But it's on a case-by-case basis. If you have something wrong with your roof, putting the salt tablets could actually make the water go into your house ... because it takes a while for that salt to work and penetrate, and create a channel through the ice dam."

Because the primary cause of ice dams is warm air leaking from the attic, the best prevention is to seal leaks with caulking or expanding spray foam, with attic insulation installed to a minimum of R-50 as space allows, according to the Commerce Department.

Insulation level are specified by R-Value. R-Value is a measure of insulation's ability to resist heat traveling through it. The higher the R-Value the better the thermal performance of the insulation, according to Energy Star, which rates energy efficiency.

Roof rakes

Nick Eades is the owner-manager of Brainerd Ace Hardware on Washington Street, which sells roof rakes.

"It is something we carry in store. It is something that we have sold a tremendous amount of this year," Eades said. "Anytime we can get our hands on more, we're grabbing them. They're very hard to come by this time of year, and just because of the year we had, they're a hot commodity."

Roof rakes are available in a few different styles and may include features that prevent the blades from shearing the asphalt from shingles, such as wheels or rollers at the bottom of the blade where it makes contact with the roof.

"There's an Avalanche rake, which has a poly slide that you start from the bottom of the roofline and push your way up, and it cuts off chunks of the snow and lets them slide down easily, so getting snow off the roof is made very simple," Eades said.

Eades said the Avalanche roof rake system is the easiest of roof rakes to use but the design makes it more expensive compared to traditional roof rakes, with retail prices around $100.

"There's everything from aluminum poles or fiberglass poles, and whether they have an aluminum or plastic head that you're pulling with," Eades said of traditional roof rakes.

Homeowners with metal roofs should avoid using roof rakes with an aluminum blade, and they need to clear the seams, which can be as tall as an inch or more.

"If you have a metal roof, you don't want use the aluminum roof rake on a metal roof. You'd like to use the plastic, just so it's not scraping and scratching," Eades said. "There are different ways of using each type of roof rake, but every one of them will work on most asphalt shingles. ... Some of it comes to personal preference, some of it comes down to the type of roof you have."

Ice dam don'ts

• Do not install heating cables. They will shorten the life of a roof and add to energy costs.

• Do not remove ice with chippers, chemicals or heat. These can damage shingles, gutters and other building components.

• Do not add roof vents, including powered vents. They will not eliminate ice dams and often make the problem worse.

Source: Minnesota Department of Commerce