Ice Damming on Roofs (Critical Things You Can Do and Avoid)

What Are Ice Dams?

Ice dams form when water from melting snow freezes into ice at the edge of your roofline. Without proper roof snow removal, icicles develop and may grow large enough to prevent water from warm air and melting snow to properly drain off your roof, causing ice damming.

When meltwater is unable to flow from the roof, it may back up underneath roof shingles, cause roof leaks, and make its way into your home or property. Inside, you may see peeling paint on your drywall, warped floors, stained and sagging ceilings, and have soggy insulation in the attic, which can invite mold and mildew.

How Does Ice Damming Form?

The following explains the process leading to the formation of ice dams:

• Heat warms the roof except at the eaves
• Snow melts but then freezes on the cold eaves
• Ice accumulates along the eaves, forming an ice dam
• Melting water backs up behind it, flows under the shingles, and into the house causing water damage

How to Prevent Ice Dams?

The key to preventing ice dams is to keep your entire roof at the same temperature as the eaves (edge of the roof). You can accomplish this by increasing ventilation, adding insulation, and sealing every possible air leak that could warm the underside of your roof.

The following are 3 relatively easy things you can do:

1. Ventilate your eaves and ridge; a ridge vent paired with continuous roof vents and soffit vents circulates cold air under the entire roof for proper attic ventilation.
2. Add attic insulation to avoid heat loss and keep heat where it belongs.
3. Attach clips and heating cables along your roof’s edge in a zigzag pattern to prevent ice dams, which equalizes your roof’s temperature by heating it from the outside instead of blowing in cold air from the inside. It is important to install these heating cables inside your downspouts too.

Do not chop at ice dams with an ice pick, hammer, chisel, or shovel. It is not only bad for your roofing but also can be dangerous for you.

If you need to replace your roof in the near-term, you might consider an ice and water barrier to prevent ice buildup installed on the roof deck (or sheathing) along the roof edges (eaves), often called “ice & water shield.” It is a thin, rubberized asphalt membrane installed below the roof shingles and typically only along the eaves and in the valleys. An ice and water barrier can protect your home from water leaks caused by ice dams and wind-driven rain. Some Colorado cities and counties require it, while many others strongly recommend it.

When building code required, roofers must install ice & water shield at the edge of the overhang and end at least 2-feet inside the nearest interior wall. Because most ice & water shield is manufactured in rolls 3 feet wide, one roll may or may not be enough. Many roofs often have a 6-foot swath of ice & water shield along their overhangs.

If you are replacing your roof through an insurance claim, this should be covered, pending your selected coverage. If not, this is a required additional cost to replace your roof to meet code. A quality roofer will also install ice & water shield in the valleys of your roof.

An ice and water barrier will not prevent ice dams. Its purpose is to reduce the chances of a leak if you get an ice dam. We recommend having an ice dam removed if it is large enough that you are concerned that the ice dam’s weight will damage your roof.