Roof rakes and ice melt tablets for roofs have been selling fast at Frattallone's Ace Hardware store in St. Paul's Macalester-Groveland neighborhood.

Earlier this week Andy Hartung picked up some salt tablets, hoping to melt a nasty ice dam he's been battling on his roof line. It's already caused a ceiling leak. He's been up on a ladder on his two-story house, chipping away at the ice with a crowbar.

"Not the smartest thing," he conceded. "But you've got to get it done. Or else it's going to get worse."

Hartung said neighbors on Facebook and other social media sites have endorsed roof ice melt. If the salt doesn't work, he said he may hire someone to steam the ice away. But the tab for that can run into the thousands of dollars.

"I'm hoping we don't [have to]. But worst case scenario, that's going to be the one of the next steps," he said.

So far this season, the Mac-Groveland Ace hardware store has sold about 500 tubs of roof ice melt and 140 roof rakes. Assistant manager Andy McRae said long-time homeowners know dealing with ice dams is part of life in the Bold North.

A lack of proper insulation in a roof may cause snow to melt on the roof. This meltwater may refreeze at the edges of the roof creating ice dams. These dams allow more water to pool on the roof. The water then may freeze and thaw damaging the roof and may even cause leaks into the house. William Lager | MPR News

"Newer homeowners are a little panicky at this point," he said. "This is their first winter episode of really dealing with ice dams, and they want all the help they can get."

The Minnesota Department of Commerce says people with homes prone to forming ice dams can try to head them off by removing snow from roofs themselves. But the department urges hiring a pro for work on the roof or a ladder, or if water is leaking inside.

The department also lists several "don'ts" to avoid damaging roofing. That includes installing heating cables, using ice chippers, chemicals or heat.

And guess what? Adding roof vents could make the problem worse.

Commerce Department spokesperson Ross Corson said ice dams are not caused by roofing, ventilation or gutter problems. The culprit is warm air from inside a house.

"Preventing ice dams is basically about making your home more energy efficient so that the warm air inside your home isn't leaking into your attic, which is what causes the snow on your roof to melt and go down to the edge and then refreeze," Corson said.

In older homes, sealing air leaks and adding as much insulation as possible will do a lot to prevent ice dams. But in extreme winters, those houses may still get build-ups of ice.

"Most older houses don't have enough space for the amount of insulation you would need, right at that edge," said Rebecca Olson, director of residential programs at the Center for Energy and Environment. "So, sometimes, you still do get some heat transfer through there. But those homes where they've taken preventative steps, typically those ice dams are less damaging and less severe."

Andy McRae, assistant manager at Frattallone's ACE Hardware, says roof ice melt and roof rakes have been selling fast. Martin Moylan | MPR News

Homes built to modern building and energy codes usually have little or no trouble with ice dams. They're much tighter and better insulated. New homes — and older homes that have been re-roofed to code requirements — also have a water and ice barrier under the shingles. It runs around the perimeter of a roof and extends up the roof past the location of interior walls, helping ward off leaks.

"It won't necessarily always be the end-all, but it's basically a sticky-backed roll of tar-like material that adheres to the decking of your roof," said John Trostle, a Federal Housing Administration-certified rehab consultant. "And even when you nail through it to install the shingles, it will seal up around those those nail penetrations."

Gutters can make ice dams worse, Trostle said.

"They'll hold that snow and ice and make the ice dam a little bit more beefy, build it up to be bigger," he said. "And sometimes that water will go across the soffits and then run down the outside wall where the under part of you eave meets the siding of the home. And in some cases ... it can start deteriorating the wood and create mold problems."

Trostle said the smart thing is to stop the heat leaks that spawn most ice dams.

"You can keep getting those ice dams steamed off every year. But if you just put some money into better ventilation, better insulation and closing those bypasses, you're saving yourself a lot of money over time," he said.

Meanwhile, shingle manufacturer GAF said it doesn't recommend the use of chemical de-icers or salts, because they can damage roofs, gutters and landscaping.

Homeowners hoping to avoid future ice dams can get inexpensive advice about how to head them off.

Xcel Energy and CenterPoint Energy offer subsidized home energy audits that can help homeowners not only find ways to reduce their heating costs but also ward off ice dams.

In suburbs with mostly newer homes, ice dams are relatively rare. But Scott Richardson, the building official for Woodbury, said ice dams still develop on newer homes in some cases.

"A lot of times your gutters will build up with ice. And then as we get a snowfall on top of snowfall on top of snowfall, it doesn't get a chance to truly melt off or run," he said.