How to Remove an Ice Dam

Calcium chloride is the chemistry you want for an ice dam, because dams form and persist at temperatures where milder de-icers have stopped doing useful work. This jug publishes -25°F on the label, which is consistent with what the chemistry can do — the University of New Hampshire Extension gives the same figure for calcium chloride generally.

What makes the 8-pound jug the right buy here is not the chemistry, it is the packaging. The standard homeowner method for a dam is to fill a tube sock or a leg of old pantyhose with calcium chloride and lay it across the dam so it melts a channel. You do that at the top of a ladder, one-handed, in the cold. A 50-pound bag is the wrong object for that job; a jug you can hold is the right one.

Be clear-eyed about the cost of using it. UNH Extension notes that calcium chloride is fast-acting but can ruin surfaces such as asphalt and concrete and injures grass and plants. On a roof, the granules that do not dissolve wash into the gutter, down the downspout and onto whatever is planted below — which is a real consideration on a bed you care about.

It is also the wrong product for the surfaces most likely to be underneath: not on pavers, not on concrete poured in the last twelve months. Our calcium chloride vs rock salt page covers that trade, and how to remove an ice dam covers the method this jug exists for.

The Snow Joe RJ205M aluminum rake we used to list is no longer available. The VEVOR is the closest comparable rake we can verify is in stock that keeps the point of this entry: an aluminum blade, for snow a poly blade cannot cut.

Aluminum earns its place on packed, crusted or refrozen snow. Poly skates over a hard crust; an aluminum edge bites into it and pulls material down the slope. VEVOR's blade is 26 inches wide, which is the widest on this page, on a handle that adjusts from 7.5 to 20 feet.

The risk is the same one that applies to every metal roof rake. Asphalt shingles are protected by mineral granules, and a metal edge dragged across them under pressure strips granules off. The damage is cumulative and shortens the roof's life. VEVOR fits wheels to the blade assembly, which help hold the edge off the surface — a genuinely useful feature — but a wheel does not guarantee the edge never touches.

So the decision is about your snow and your roof. On a metal roof, or where you routinely face crust, it is the right tool. On an asphalt shingle roof that only sees fresh snow, the poly rake above does the job without the granule risk.

The Green Gobbler calcium chloride we used to list here is no longer available. Peladow is the closest comparable product we can verify is in stock, and it is the reference calcium chloride pellet that most of the category is measured against: made by OxyChem, at about 90% calcium chloride.

The reason to reach for calcium chloride is its mechanism. It dissolves exothermically — it releases heat as it goes into solution — so it starts working the moment it lands rather than depending on sunlight or ambient warmth. OxyChem also points to the round pellet shape, which penetrates an ice layer and attacks the bond with the pavement instead of sitting on top.

Be precise about the temperature. OxyChem publishes an effective temperature of -25°F. That is very cold, and it is consistent with the chemistry: the Minnesota Pollution Control Agency puts calcium chloride's lowest practical pavement temperature at -20°F, ten degrees colder than magnesium chloride's. Calcium chloride wins on both counts that matter in deep cold — it works colder, and it starts faster on an existing bond.

The cost is what it does to surfaces. Calcium chloride drives the most freeze-thaw cycling of any common de-icer, which is the mechanism that damages concrete, and its brine washes jointing sand out of pavers. Use it to rescue a driveway that has already iced — how to get ice off a driveway — not as routine pre-treatment.

This is the kit most people end up buying, and the specification explains why: 100 feet at a published 5 watts per foot on a standard 120-volt outdoor outlet, arriving pre-assembled with the spacers and shingle clips already in the box.

Those clips matter more than the listing makes them sound. The cable has to be held in a zigzag along the eave at a consistent spacing, and it has to be attached without putting a fastener through the roofing. The clips are the entire mechanism for doing that, and buying a bare cable without them means a second order before you can start.

The thermostat is the other feature worth paying for. A heat cable with no control is a 500-watt appliance that runs whenever it is plugged in, which is how people end up shocked by a January bill. Frost King states the kit switches on and off automatically with temperature.

The honest limitation is that it is constant wattage rather than self-regulating. Every foot draws the same power whether it is buried in an ice dam or sitting in dry air, and — more importantly — if the cable touches or crosses itself, the heat concentrates at that point rather than backing off. Self-regulating cable is designed to tolerate exactly that, and it is the upgrade worth understanding before you buy.

Before ordering any length, read the section on this page about what a heat cable does and does not fix. It manages a symptom. The cause is heat leaking into your attic, and that is an insulation job — the same argument we make about roof rakes.

Roof valleys are where two roof planes meet, and they concentrate meltwater from both. They are also the place eave-run heat cable does least good, because a zigzag of cable clipped along a roof edge does not follow a valley down.

This is the product for that specific failure. It is a mat rather than a cable, sized to sit in the valley, rated by the maker at 50 watts per foot — an order of magnitude more heat per foot than the 5 W/ft cable most people run along an eave.

That output is the reason for both the appeal and the caution. It is enough to keep a valley draining in weather that defeats ordinary cable, and it is a serious electrical load: the maker offers lengths up to 50 feet, which at 50 watts a foot is 2,500 watts on one run. That is a dedicated-circuit conversation before it is a shopping decision.

The install is the other consideration. It fastens into the valley with supplied grommet screws, and a valley is the least forgiving part of a roof to put fasteners through. If that sentence makes you uneasy, it should — this is a fair-weather job for someone comfortable on a roof, or a job for a roofer.

None of that helps with water coming through a ceiling tonight. For that, see how to remove an ice dam; for the ordinary eave version of this hardware, see roof heat cable.