What Causes Ice Dams and How To Prevent Them

If you live in a region where winter occasionally brings below-freezing weather and accumulating snow, ice dams are a reality. Homeowners in these parts of the country know that ice dams can cause significant roof damage. But what causes ice dams? How can a homeowner prevent ice dams from occurring? We address these questions and give you solutions for what to do if you experience an ice dam on your roof.

What Are Ice Dams?

ice dams with icicles on roof's edge

An ice dam is a buildup on the eaves and overhangs of sloped or inclined roofing. This collection of ice develops on the roofs of heated buildings, homes, and other structures. Heat escapes a building’s interior through the roof, causing snow to melt.

The melted snow (i.e., meltwater) cascades downward to the eaves and overhangs of the structure. It then re-freezes into ice and impedes the drainage of additional meltwater, resulting in a damming effect, commonly referred to as an ice dam.

What Causes Ice Dams?

Following a snowfall, snow amasses and remains on the roof. This snowpack forms an insulating layer under climatic conditions that would usually cause the freezing point to exist within the snow layer if the snow was not subject to melting. Instead, heat escaping through the roof’s exterior surface melts the snowpack. 

Gravity pushes the melted snow (i.e., meltwater) down the roof’s sloped incline to the edge (i.e., the eave or overhang). Unfortunately, there is no building heat at the roof’s edge typically. Assuming climatic conditions remain below freezing, the meltwater re-freezes and formulates into ice. This ice begins piling up.

The ice buildup at the roof’s perimeter now acts as a barrier impeding the further passage of meltwater off the roof. Additional meltwater backs up and forms into ice. Eventually, excess meltwater & ice can back up under shingles and cause the roof to leak or create other damage, including structural, insulation, and interior issues.

How To Prevent Ice Dams

As a homeowner, you should consider ice dam prevention techniques to avoid the far costlier effects of damage to your home from an unmitigated ice dam disaster.

Address Attic Ventilation Issues

Proper venting allows the attic air to remain cold enough to minimize or eliminate the freeze/thaw cycle on the roof. Installing a ridge vent and continuous soffit vents allows cold air to circulate evenly throughout the roofing system. An efficient ventilation system becomes an effective deterrent to the formation of ice dams.

Clean Rain Gutters And Downspouts

Routinely cleaning rain gutters and downspouts, especially in the autumn and winter, helps ensure that meltwater channels through the gutter system efficiently. A clogged gutter prevents meltwater from exiting the roof and makes it far easier for ice dams to form. Remove leaves, sticks, branches, and debris from the gutters.

Ensure Sufficient Attic Insulation

contractor installing attic insulation between rafters



Inadequate attic insulation creates an imbalance, causing heat to escape from the home through the attic just below the roof’s surface. Consequently, the snowpack melts, eventually forming an ice dam. Ideally, attic insulation should have an R-value of at least R-30 (R-38 in northern climates) to reduce or prevent heat loss. Adding insulation can greatly reduce the formation of ice dams. When coupled with proper attic ventilation, insulation has more benefits than just eliminating ice dams. It will increase the comfort of your home by stabilizing the temperature. It will also reduce your heating and cooling bills for years to come.

Prevent Heat Loss By Sealing Off Air Leaks

Warm air rises. Even with an ideal ventilation system in place, heat will escape from your home through your roof if you fail to secure exterior gaps. Adding insulating foam to openings around vent pipes, bathroom vents, dryer vents, skylights, and chimneys allows an airtight seal to formulate. Airflow leaks are no longer an issue.

Remove Excess Snow From the Roof

Heavy snow loads on the roof eventually melt. When a roof possesses excess snow, the chance of an ice dam forming increases substantially. Avoid this outcome. Safely use a long-handled roof rake from the ground and remove snow from the roof. Be sure that the rake does not scrape the shingles, as this can cause damage. Taking this precaution also reduces the likelihood of the roof sagging or collapsing.

If you observe the formation of an ice dam on your roof, take immediate action. Do not risk an ice dam causing catastrophic property damage. 

Hire A Professional Roofer To Remove The Ice Dam

A knowledgeable and experienced roofing contractor has the tools and equipment to mount the roof safely and apply the most effective solution.

If you find that your roof tends to form ice dams, or if you have other roofing issues that need to be addressed, reach out to Quantum Roofing.

We serve residential roofing customers in North Carolina, South Carolina, and Tennessee. We have the expertise to handle your roof repair or replacement project efficiently and affordably. Contact us today to schedule your free consultation.


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