While icicles hanging from your roof's eaves have a certain charm and evoke nostalgic childhood memories, they're often caused by ice dams that form along your gutters. First of all, it's not normal for ice dams to form. If you have them, that means you have an underlying problem with heating and cooling at the eaves of you house that needs to be looked at by a professional. But that's a long-term solution. Dealing with ice dams right now is your immediate concern, especially if you're getting water leaks in your ceiling and down your walls.
What Not to Try
Just to be clear, it's never a good idea to climb up a ladder and start hacking away at an ice dam with an axe or ice pick. It's also a bad idea to use a chainsaw or blowtorch. You run the very real risk of damaging your roof or gutters, injuring your hand or arm, burning yourself or your house, or falling off the ladder. No matter how much you might be tempted, do not attempt these techniques. Avoid climbing a ladder in the winter too. The ground will either be covered in snow or ice, or be slick or wet. This makes for an unstable ladder, not to mention poor footing as you climb.
Box Fan in Attic
If you're experiencing a leak in your home because of an ice dam, position a box fan in your attic so it's aimed at the underside of the roof where the water is leaking in. This blows cold air onto the water and freeze it. If the weather's cold enough, you could freeze the water in a matter of minutes. Be careful mixing water and electricity. Plug your fan into an extension cord before taking it up to the attic, then plug it in where you're safely away from the water.
This solution works best to slow the growth of ice dams, and as a preventive measure. While standing on the ground, use a long-handled aluminum roof rake to pull snow off of the roof. Again, do not climb on a ladder to do this, and avoid any electrical wires running into your house. If you follow these basic safety precautions, raking your roof is a perfectly acceptable way to inhibit the size of ice dams, thus keeping your problem to a minimum. Since the roof rake removes snow, it changes the exterior temperature of your roof, which slows the growth and spread of ice dams.
Calcium Magnesium Acetate in Pantyhose
Some experts suggest cutting old pantyhose off at the top of the leg, then filling the hose with an ice-melt product. One problem with this method is that ice melt products are corrosive and can damage the metal portions of your roof. Calcium magnesium acetate is the least corrosive ice melt, so use it instead of others if you try this method. Fill the leg of the hose, leaving room at the top to tie it off. Toss the packet up onto the roof while standing on the ground. Use an extension pole with a hook on the end to remove the rope and move the tube into position on the roof. Lay the tube of ice melt on the roof so it crosses the ice dam perpendicular to the gutter. This position is necessary because it's best for forming channels that give the melting ice a path off your roof. You'll likely need several pairs of pantyhose, depending on the size of your ice dam. You'll also need to reposition the ice melt from time to time, and add new hose as the CMA melts.
Steaming ice dams is a job best left to professionals with years of experience. Several methods are used, but they involve loosening the grip of the ice from the roof, eaves and gutters so that the ice can be lifted and dropped off the roof. The size of the chunks of ice should be controlled, so that no damage to your gutters, house or landscaping occurs. Look for a company that's licensed, insured, and can provide good references. Under no circumstances should you attempt to steam ice dams yourself. The equipment is highly specialized and expensive, and the procedure requires skill to perform it safely and effectively.