Ice Dams: Chicago's #1 Winter Roof Problem

Ice dams form when heat escaping through the attic melts snow on the upper roof, and the meltwater refreezes at the colder eave edge. The resulting ice ridge traps water behind it, which can back up under shingles and leak into your home. Chicago's cycle of heavy snow followed by brief warm spells makes ice dams extremely common.

Prevention starts in the attic: proper insulation (R-49 recommended for northern Illinois) and ventilation keep the roof deck uniformly cold so snow melts evenly. During construction or replacement, installing ice-and-water shield membrane 3 to 6 feet from the eave edge provides a critical second line of defense.

Snow Load and Structural Stress

While most residential roofs in the Chicago area are engineered to handle typical snow loads (around 25 lbs per square foot), successive storms without melting can push accumulations to concerning levels. Wet, heavy snow weighs significantly more than dry powder — a foot of packed wet snow can approach 20 lbs per square foot.

If you notice interior doors sticking, cracking sounds from the attic, or visible sagging in the roofline after heavy snow, these are signs of excessive load. Carefully removing snow with a roof rake (from the ground) can relieve pressure, but avoid chipping at ice with sharp tools, which can damage shingles.

Freeze-Thaw Cycle Damage

Chicago often experiences temperature swings above and below freezing multiple times in a single week during winter. Each cycle allows water to seep into tiny gaps in flashing, caulking, and shingle edges, then expand when it refreezes. Over a season, this process can open up significant entry points for water.

Flashing around chimneys, skylights, and wall-to-roof transitions is particularly vulnerable. Annual inspection of these areas — ideally in fall before the freeze cycle begins — helps catch deterioration early. Replacing cracked caulking and resealing flashing joints is inexpensive preventive maintenance.

Emergency Winter Repairs

If a winter leak develops, the first priority is preventing interior damage. Place buckets to catch dripping water, move valuables away from the area, and call a roofing contractor immediately. Emergency tarping can stop active leaks until weather permits a permanent repair.

Cornerstone Roofing Co. offers emergency response services throughout the winter season. We can tarp an active leak within hours and schedule a full repair as soon as conditions allow. Do not attempt to climb onto an icy or snow-covered roof yourself — the risk of falls is extreme.

Spring Inspection: Catching Winter Damage Early

Once winter breaks, schedule a professional roof inspection before spring rains begin. Winter damage is often invisible from the ground — lifted flashing, cracked pipe boots, and shingle displacement from ice are common findings that, if unaddressed, will leak during the first heavy rain.

A thorough spring inspection also provides documentation that is valuable if you later discover interior damage covered by your homeowner's insurance. Catching and documenting issues promptly strengthens any future claim.