The Cause

What Causes an Ice Dam?

Ice dams typically begin when heat reaching the roof deck causes snow on an upper portion of the roof to melt.

The resulting water travels down the roof toward the eaves. The roof edge can remain colder because it extends beyond the heated portion of the house.

When the meltwater reaches this colder area, it can freeze again.

Repeated melting and freezing can gradually create a ridge of ice along the lower edge of the roof. Water from additional melting snow can then collect behind that ridge instead of draining normally.

The ice visible along the edge of the roof is often a symptom of a temperature difference occurring higher on the roof.

Asphalt shingles are primarily designed to shed water moving down the roof. Water trapped behind an ice dam can expose shingles, flashing, valleys, and other roof details to conditions they do not normally experience during an ordinary rainstorm.

NEPA Winters

Why Ice Dams Are Common During Northeast Pennsylvania Winters

Northeast Pennsylvania winters can bring snow, extended freezing temperatures, warmer daytime periods, and repeated freeze-and-thaw cycles.

Those changing conditions can create an environment where snow melts during one part of the day and freezes again near the roof edge.

The construction of the house matters too. Older homes, additions, dormers, knee-wall spaces, valleys, and complicated rooflines can have sections that lose heat differently from the rest of the building.

Prevention

Preventing Ice Dams Starts With Controlling Heat

Removing visible ice may help with an immediate problem, but it does not necessarily correct the condition that caused the ice dam.

When ice dams repeatedly develop in the same areas, it can be useful to look at how heat is moving from the living space into the attic and toward the roof deck.

Air Seal the Attic Floor

Openings between the living space and attic can allow heated indoor air to move upward.

Common areas can include attic access openings, plumbing and electrical penetrations, ductwork, framing connections, and other gaps in the ceiling plane.

Reducing unnecessary air movement into an unconditioned attic can help keep roof temperatures more consistent during cold weather.

Check the Insulation

Insulation helps slow heat transfer from the heated portion of the home. Uneven insulation can create warmer sections of roof deck.

This can help explain why snow disappears from one section of a roof while remaining on another.

If ice repeatedly forms in the same area, an insulation or home-energy professional may be able to identify areas where heat loss is contributing to the problem.

Evaluate the Ventilation System

Proper attic ventilation can help maintain more consistent attic conditions, but simply adding a ridge vent does not automatically solve an ice-dam problem.

A ventilation system needs an appropriate intake and exhaust path and should work together with the home's insulation and air-sealing strategy.

A seasonal roof tune-up before winter can also provide an opportunity to check visible roofing details before snow and freezing weather arrive.

Roof Protection

How the Roofing System Helps Protect the Home

Roofing materials cannot correct excessive heat loss from inside a house. However, the way the roofing system is installed can provide important protection when snow and ice are present.

Ice and Water Barrier Does Not Prevent the Ice Dam

This distinction matters. Ice and water barrier helps protect the roof deck if water backs up beneath the shingles, but it does not stop snow from melting and freezing at the roof edge.

The material is a layer of protection against water intrusion rather than a cure for the conditions creating the ice.

Flashing Becomes Especially Important

Snow and ice can hold moisture against chimneys, walls, valleys, and roof transitions longer than a typical rainstorm.

Our guide to roof flashing around chimneys and skylights explains why these transition areas are so important to keeping water out.

Roof Decking Can Reveal Past Moisture Problems

During a full tear-off roof replacement, removing the existing roofing gives the contractor an opportunity to inspect the wood underneath before the new roofing system is installed.

Learn more about what can happen when moisture reaches the structure in our guide to rotted roof decking and damaged roof sheathing .

You can also see how these major components work together on our roof replacement page .

After Ice Forms

What Should You Do If an Ice Dam Has Already Formed?

Once significant ice has formed along the roof, the focus shifts from prevention to reducing the chance of injury and limiting additional damage.

Climbing onto a snow- or ice-covered roof can create a serious fall hazard.

Homeowners should also avoid striking or chopping ice with hammers, axes, shovels, or other tools that could damage shingles, flashing, gutters, or the roof underneath.

Removing Snow From the Ground

In some situations, reducing snow accumulation near the lower portion of the roof may reduce the amount of meltwater feeding an existing ice dam.

Roof rakes designed for snow removal allow some of this work to be performed from the ground.

A roof rake still needs to be used carefully. The goal is to remove some of the snow rather than aggressively scrape the shingles or other roofing materials.

When Water Has Already Entered the Home

If water has reached a ceiling, wall, attic, or other interior area, removing the visible ice is only part of the concern.

The roof should also be evaluated for the path the water took and whether shingles, flashing, decking, insulation, or interior materials were affected.

Our guide to what to do during an emergency roof leak covers the immediate steps homeowners can take while arranging for the roof to be evaluated.

If you suspect the roofing system itself has been damaged, visit our roof repair page for more information.

Gutters

Do Clogged Gutters Cause Ice Dams?

Gutters often get blamed for ice dams because some of the most visible ice appears along the gutter and roof edge.

However, a clogged gutter does not usually explain why snow is melting farther up the roof in the first place.

Uneven roof temperatures and heat reaching the roof deck are often more important parts of the ice-dam process.

That does not mean gutters should be ignored. Gutters and downspouts still need to move water away from the roof edge and home when temperatures are above freezing.

Debris can interfere with drainage and contribute to other moisture problems around the home.

We explain that issue separately in how clogged gutters can cause hidden water damage .

Recurring Problems

Why Ice Dams Sometimes Keep Coming Back

A home that develops ice dams in the same location winter after winter may have an underlying condition that removing the ice alone will not correct.

Recurring ice buildup is a reason to look at the house as a complete system.

Air leakage, insulation, attic ventilation, roof geometry, flashing, roofing materials, and previous construction changes can all affect how the roof behaves when it is covered with snow.

The location of recurring ice can sometimes provide useful clues about what is happening below that particular section of roof.

Heavy buildup below one dormer, addition, attic area, or roof transition may point toward a localized condition rather than a problem affecting the entire roof.