Ice Dams in Wisconsin: Warning Signs, Causes, and How to Prevent Them

Ice dams are common in northern climates, especially Wisconsin. Ice dams are a serious problem and can cause roof leaks, interior water damage, gutter damage, mold & mildew growth, and premature roof failure.  To help protect your roof and home from potential damage, it is important to know what an ice dam is, how they form, and how to prevent ice dams.

What is an Ice Dam?

An ice dam is the accumulation of ice along the edge of the roof that prevents melting snow from draining. When water backs up behind the ridge of ice, it can leak into the home and cause damage to insulation, walls, ceilings, etc. Also, leaks and moisture in the home can lead to the growth of mold and mildew.

Common Signs of Ice Dams on Your Roof:

• Icicles along the roofs edge & gutters

• Ice buildup along the roof edge or behind gutters

• Water stains on ceilings or walls

• Sagging ceilings or bubbling drywall

• Peeling paint or discoloration on interior walls

• Moisture or frost in the attic

• Mold or mildew odors indoors

These signs are especially common after heavy snowfall followed by freeze–thaw cycles, which are typical in northern climates like Wisconsin.

How Does an Ice Dam Form?

Ice dams form when the temperature in your attic is above freezing temperature, while the outside of the home is below freezing. Nonuniform roof surface temperature causes ice dams.

Ice dams form when:

1. Heat escapes into the attic warming the roof deck to a temperature above freezing

2. The heated roof deck melts the snow above

3. Initially, the water flows downward towards the overhang and refreezes due to cold outdoor temperatures. The ice dam will only form on the portion of the roof that is below freezing.

4. Once a dam has formed along the cold edges of the roof, the water continues to flow downward, backs up under shingles, and finds cracks into the exterior roof that allows it to leak inside the home.

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What Causes an Ice Dam?

Ice dams are typically caused by the following factors:

Improper Insulation

Improper insulation allows warm air to escape to the attic and heat your roof deck.

Improper Ventilation

Improper ventilation allows warm air to linger long enough to heat your roof deck.

Location of Your Home

Location of your home in terms of climate, exposure to sun, tree coverage, etc. Ice dams are common after several days of melting-freezing cycles. Snow melts during the day, then refreezes when temperatures drop overnight.

How do I prevent Ice Dams?

To prevent ice dams, the roof temperature needs to be the same as the overhang. To prevent ice dams, your best bet is to change how warm air flows within your home.

Add Insulation

Add insulation in the attic. You may want to get a professional inspection and quote to determine exactly how much insulation is needed and where. Most experts agree the R-value of attic insulation should be at least R-30 (R-38 is preferable in northern climates).

Improve Ventilation

Improve ventilation in the attic to allow heat to dissipate. Continuous air flow prevents hot air from lingering long enough to warm the roof deck and melt the snow above.

Seal Any Gaps

Seal any gaps that allow warm air to leak into the attic. Look at the attic hatch, house fans, and plumbing vents.

Keep Your Gutters Clear

Always clean your gutters in fall! Clear gutters help provide blockages that can cause water to back up and help prevent ice dams.

Remove the Snow

Use a roof rake to remove the snow from the roof. Aim to clear the bottom 3-6 feet of snow at the very least. This can be dangerous so make sure you take the right precautions or hire a professional.

FAQs

Can ice dams cause roof leaks?

Yes. Ice dams prevent melting snow from draining properly. As water backs up behind the ice, it can work its way under shingles and leak into the home. These leaks can cause damage to ceilings, walls, insulation, and even structural components.

Are ice dams covered by homeowners insurance?

Coverage depends on your policy. Some insurance plans may cover interior water damage caused by ice dams, but they often do not cover the cost of removing the ice dam or repairing underlying issues like poor insulation or ventilation. It’s best to review your policy or contact your insurance provider for details.

Do ice dams mean I need a new roof?

Not necessarily. Ice dams are usually caused by heat loss from the attic due to inadequate insulation or ventilation—not by the roofing material itself. However, repeated ice dam issues can lead to roof damage over time, which may require repairs or replacement.

Can a new roof still get ice dams?

Yes. Even newly installed roofs can develop ice dams if attic insulation, ventilation, or air sealing issues are not addressed. Ice dams are more about temperature differences on the roof than the age of the shingles.

How cold does it need to be for ice dams to form?

Ice dams typically form when daytime temperatures rise above freezing, allowing snow to melt, followed by nighttime temperatures below freezing. These freeze–thaw cycles are common during Wisconsin winters and create ideal conditions for ice dam formation.

Is it safe to remove ice dams myself?

Ice dam removal can be dangerous and may cause roof damage if done improperly. Using sharp tools or climbing onto an icy roof increases the risk of injury and leaks. In many cases, it’s safer to hire a professional with the proper equipment and experience.

Contact PK Contractors

Ice dams are a common winter problem in Wisconsin, but they’re also preventable. Proper insulation, ventilation, and sealing can protect your roof and home from costly damage. If you’re concerned about ice dams or recurring winter roof issues, a professional inspection can help identify the root cause before problems get worse. Contact us to schedule an estimate!

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