Ice Damming on Your Roof: Treat Current Issues and Prevent Future Problems

It’s a common “one-two punch” during New Jersey winters. First, the heavy snow, then the icicles and ice dams. Although we marvel at the size and beauty of those icicles, we often ignore the ice dams until they cause leaks.

What Exactly is Ice Damming?ice damming on roof

Ice damming on a roof consists of ice buildup serious enough to prevent water from efficiently flowing to the gutters and downspouts. Just like a lake forms behind a dam, pools of water collect behind ice dams on a roof.

Reasons for Ice Damming

Ice damming on a roof is often caused by the temperature difference between warmer areas directly above the attic and the colder outer edges. At other times, it is caused by water backing up above clogged gutters. Water freezing along the outer perimeter of the roof creates dams made of ice.

Fortunately, most NJ homeowners can reduce ice damming by addressing common causes.

Clogged gutters

First, make sure that your gutters and downspouts are clear of debris. It doesn’t take long for a morass of twigs and leaves to clog a gutter. Water backs up onto the roof where it freezes and as temperatures drop below freezing. Repeat this cycle for a few days in a row, and serious ice damming is often the result.

Inadequate roof insulation or ventilation

Homes with inadequate roof ventilation and attic insulation are particularly vulnerable to ice damming because warm, humid air from the living area can heat up the roof deck enough to melt the snow on it. The water flows to the colder outer edges of the roof where it freezes.

Blocked vents

Even if you have a good system for roof ventilation, you’ll only reap the benefits if the vents are free of debris. For example, a blocked soffit vent will quickly reduce the airflow you need to clear moist, warm air from your attic that tends to increase ice damming in the winter.

Problems Caused by Ice Damming

Ice dams can cause a variety of very different headaches, including leaks, excess roof loads and mold.

Leaks from water backup

Water collecting above an ice dam can work its way under the shingles. Once the water gets through any breach in the felt or underlayment, it can find gaps in the sheathing. From there the moisture can get to the roof’s framing, the attic insulation and even the living space itself.

Excessive roof loads

The good news is that ice weighs five pounds per cubic foot less than water. The bad news that it still weighs 57 pounds per cubic foot. It’s easy to see that ice dams can quickly add many hundreds or thousands of pounds to the load on your roof. One of the insidious qualities of widespread ice damming is the strain it puts on the roof.

Older roofs are often most vulnerable. Roofs with multiple layers of shingles are also relatively more vulnerable. When a section of a roof collapses, extensive repairs to the framing, sheathing, underlayment and shingles are all required.

Mold formation

While mold is not the most common issue caused by ice damming, it can occur if the ice dams are not properly taken care of.

When water backs up behind the ice, it can work its way under the shingles and into the sub-roofing. Once the moisture gets inside your home, it can cause mold to thrive in many places, including the drywall, wood studs, insulation, wallpaper, ceiling tiles and carpet.

Preventing Ice Damming: A Proactive Approach

Good roof ventilation and proper attic insulation reduce ice damming by modifying attic air temperatures.


To reduce ice damming and to improve your home’s energy efficiency, use a certified inspector to determine whether your attic insulation is sufficient. In the Tri-state area, R-38 insulation is recommended.

Even when there’s a good layer of insulation covering your attic floor, uninsulated ductwork in your attic can be a source of warm, moist air. To remedy this problem, it’s necessary to properly insulate the ducts and to fix any leaky ductwork.


Ensure that there is a free flow of air through your attic to eliminate warm, moist air from your attic before it leads to ice dams.

Make sure your soffit vents, gable vents and roof vents are all free of debris to promote good ventilation in the open space below your roof. When venting is clogged, warm air from your living space can increase the melting of snow on your roof.

Even when you can’t completely eliminate ice dams, you can take steps to minimize their impact. An ice and water barrier provides a tough, waterproof layer of protection on top of the regular felt or synthetic underlayment. This special product can be selectively installed along the eaves, around valleys and anywhere else ice damming is a common concern. Major roofing manufacturers like GAF and Owens Corning manufacture a number of such barriers, also known as ice and water shield.

Contact CRS for Prompt Assistanceice damming on roof

Since 1977, CRS has addressed every kind of roof problem faced by NJ homeowners, including ice damming on a roof. CRS is a full-service roofing company serving Bergen, Passaic, Essex counties and beyond with certified roof inspections, routine maintenance and repairs, updated roof ventilation, emergency repairs, re-roofing and full roof replacements.

We are factory-certified by both GAF and Owens Corning. Look to a northern NJ roofing company that these industry leaders trust. To schedule a visit by our certified roof inspector, please contact us.

New Call-to-action

CRS provides full-service roofing including residential roof repair and replacement services, siding installation and replacement, regular roof maintenance, solar shingle installation, and more to homeowners in northern New Jersey from Bergen County to Somerset and Hunterdon Counties. We are local, experienced, and factory-certified by trusted industry names like GAF and Owens Corning. The experienced team at CRS would welcome the opportunity to serve you with the same level of customer service we’ve provided to thousands of other New Jersey homeowners since 1977. We also offer commercial roofing services to the tri-state area and have been trusted by local business owners to keep their employees and businesses safe through all seasons. 



You May Also Like