How to Prevent Ice Dam Formation on Your Roof

Ice dams pose a significant threat and can lead to extensive water damage, but there are many things you can do to your property to prevent ice dam formation. And, boy, if you've ever had an ice dam, you'll agree that prevention should rise to the top of your to-do list.

What are ice dams?

Ice dams are particularly common during the winter in colder environments. "As snow lays on your roof, a pattern of thawing and re-freezing can occur," shares Michael DiMartino, SVP of Installations at Power Home Remodeling. "If that ice forms along the edge of your roof, it creates a 'dam' that blocks melting snow from properly draining off. That built-up liquid can then seep into your roof shingles and eventually cause leaking inside your home. It can also result in major weight that your roof isn’t prepared to hold especially if your home has been re-roofed (when a new roof is added on top of an old roof)."

Is there anything you can do to cure an ice dam that's forming?

Unfortunately, not. "Think of it this way," shares DiMartino. "How do you prevent a flat tire after you have one? It’s not possible. You must fix or replace the tire. The same goes for ice dams that have already formed."

There are only two ways snow can melt on a roof:

• Heat that escapes up through the attic

• Sun that beats down from the sky on a winter day

Can I put rock salt on my shingles to melt the ice?

We'd love to say that it works, but it doesn't. Rock salt only melts ice between 20° and 32° F, and even then, it would take a lot of rock salt to chew through the ice that forms on your shingles. Plus, it would leave a stubborn residue on your shingles and its runoff would risk damaging the soil and plant life around your home. For what it's worth, we've tried the technique where you fill a pair of pantyhose with salt and lay it in a gutter to treat the buildup of ice—it's also ineffective. (Also, eager homeowners, don't get up on an icy roof; you're asking for an urgent care visit.)

7 Ways to Prevent Ice Dams Before They Start

1. Install an Ice and Water Shield for Added Protection

Using proper amounts of ice and water shield can help protect your home against ice dams. "Ice and water shield doesn’t prevent the formation of ice dams, but it's a good prevention strategy," cautions DiMartino. "As I always say, water finds a way in and it wins every time, so it is important to put every possible barrier in place to mitigate that. The ice and water shield is a layer that protects the roof from ice damming and is particularly important for homeowners in northern regions that experience more snow and sleet.

He adds, "The shield must run 24” beyond the warm wall of a home. You can double this, or even triple it (but there are added costs in doing so). The amount you need is dependent on the roof eaves, and also the pitch of the roof. The steeper the roof slope, the less ice and water shield you would need. Any ice damming above the ice and water shield would be sitting on the bare plywood or roof sheathing, making it much easier for the roof to leak, or rot."

2. Use a Roof Rake

You can help mitigate ice dam damage by using a roof rake to clear snow from the valleys and the roof edge. You won't be able to clear the entire roof, but that's not usually necessary. You want to focus on removing the source of the melted snow (meltwater) that easily refreezes to form icicles and roof ice dams. It's often advised to use the snow rake if you've received over 6" of snow.

3. Install Proper Attic Insulation

Proper insulation can prevent ice dams from forming in the first place. "Your attic should be insulated according to the values determined by Energy Star, as the specific requirements differ depending on your state and building code," shares DiMartino. "If your attic is under-insulated, you likely have a warm roof. This allows heat from the living spaces to rise and melt any snow or ice on the roof. In addition to ice dam formation, higher levels of attic moisture can also lead to mold-like growth." (Bonus: Once your attic floor receives additional insulation, you'll see a savings in your energy costs.)

Related: The Real Reasons You Need Better Attic Insulation

4. Add Roof Vents

Proper roof ventilation is a permanent ice dam solution that protects against ice buildup. "Your house has to breathe, so don't ignore your attic ventilation. It’s industry standard to install an elevated ridge vent, and shingle over it," shares DiMartino. "The small perforations are protected by breathable fabric behind the slots. Nowadays, it’s easy to spot homes that have ridge vents, and those that do not."

He adds, "If you’re thinking about investing in a new roof, it’s a good idea to also have intake vents installed, along with soffit vents and gable vents. Intake vents are placed lower on a roof, so that air is circulating throughout the entire attic space, not just at the highest point. It’s also important for any vents from different areas of the home to go through the roof (not be rerouted into the attic space). This includes things like a dryer vent, stove vent, or bathroom exhaust fan. You want to make sure that no moisture or condensation is being pumped into an attic space that lacks proper ventilation."

5. Use Synthetic Underlayment (Instead of Felt Paper)

Underneath the layer of shingles is a roofing underlayment that works as a vapor barrier to protect your home against the natural elements. Without the underlayment, your roofing system would fail within only a few years. Traditionally, felt paper was the main underlayment option because it was treated with a petroleum-based product, making it water-resistant, but advancements in roofing materials have come a long way as manufacturers look to reduce heat loss and roof leaks.

DiMartino attests to the changes in industry standards. "Nowadays, manufacturers have developed more modern options like GAF’s Deck-Armor, which is made of synthetic and similar to the fabric of a Gore-Tex jacket, so it can be cut, but not torn. I recommend going with a more durable and breathable underlayment because felt paper can be torn easily during the installment process."

6. Keep Gutters Clear

Clogged gutters can't drain, and when they can't drain, they can freeze and cause ice damming which leads to interior leaks. "I like to clean them as part of my routine maintenance to ensure they’re diverting water away from the home," shares DiMartino. "Aside from ice damming, it’s also important to keep your gutters clear to prevent icicles from forming. If water can’t drain out properly, this can lead to collected precipitation which freezes and adds unnecessary weight and stress on the gutters. If these icicles become heavy enough, they can cause greater gutter, soffit and fascia board damage."

He adds, "If your gutters are compromised, which means precipitation is getting behind your gutter and dripping down, refastening the gutter to its proper position is a key step in allowing it to function properly. Even if you have gutter guards installed (which homeowners often assume prevents them from needing to maintain their gutters long-term), it’s still important to head up on a ladder and check out what’s happening."

Related: Three Outdoor Chores Worth Doing in the Winter

7. Install Roof Melting Heat Cables

A.K.A. roof de-icing cables, this heated cable system is installed along the edge of the roof and in gutters and downspouts. When the electric cables are turned on, they generate heat to melt snow and ice and allow water to flow off the roof.

These electric heat cables come in various types and designs, including self-regulating cables that automatically adjust their heat output based on the surrounding outdoor temperature, and constant wattage cables that provide a consistent level of heat. Installed using a zigzag pattern, they are typically controlled by a thermostat or timer to activate only when needed to optimize energy efficiency.