What is an Ice Dam?

An ice dam is a build up of ice and snow which forms along the edge of a roof starting at the edge of the exterior wall and extending over the eaves. This happens for two reasons. ICE_DAM_2The first reason is from snow being melted by a warm ceiling.  This warm ceiling is caused by heat from the building structure transmitting  through the insulation and warming the air in the attic. As a result, the roof deck melts the snow from the bottom side of the snow pack. The outer portions of the roof deck along the eaves are colder due to the fact they do not have a warm structure under them like the rest of the roof.  This is the point at which the ice dam normally starts.

The second reason an ice dam forms is from melting snow from the warmth of the sun during the day. This melting snow contributes to the ice dams but most often results in icicles forming along the eaves.

An ice dam can cause water to pool and backup along the roof eave which can lead to leaks as water can get under the roofing shingle overlaps and even under the underlayment overlaps. To help prevent against these leaks it is recommended to use a self-adhered underlayment. A self-adhered underlayment adheres to the roof deck preventing water intrusion or ice from forming between the deck and the self-adhered underlayment. Water infiltration can cause roof rot or damage to the roof deck.

Ice Damming Protection

In areas where there is a history of ice forming along the eaves (Ice Dams), causing melt-water to back up under the shingles, a self-adhered peel and stick underlayment should be installed at the roof edge. This self-adhered membrane is often referred to as ice and water barrier and is typically a self-sealing, self-adhering waterproof underlayment.
Ice Dam Illustration

The International Residential Code (IRC) is the residential building code most widely adopted in the U.S. According to the IRC, the ice barrier should extend from the lower roof edge to a point at least 24 inches in from the outside of the exterior wall, measured level.

All other roofing industry organizations specify that the 24 inches be measured from the inside of the exterior wall.

Source: http://www.nachi.org/underlayment-general.htm

For more information on ventilation, please visit:


Correctly installed Titanium® PSU30 and UDL30 can protect your roof from the damaging effects caused by ice dams, water infiltration, snow and wind-driven rain.

3 Steps to combat Ice Damming:

1. Protect your roof deck against damage caused by Ice DammingIceDamming

a. Contact your local Building Code Inspection Department in your area and they can provide you with the minimum and recommended requirements for roof deck application of an Ice Damming Peel and Stick product.

b. Your local building code will most likely recommended to apply a Peel and Stick underlayment on the first two layers of the roof deck.  Building code will indicate how many inches up from the eave and beyond the warm side of the  inside wall the Peel and Stick underlayment should be installed.

c. The amount of Ice Damming Peel and Stick will depend on: your region,  elevation of your home, roof pitch, and the amount the eave extends from the side wall of the home.

d. Applying an approved Ice Damming product will offer the best possible protection against roof deck failure in ice damming environments.

Check Attic Insulation meets local building code

a. Check with your local building code for the recommended insulation R value. See the Department of Energy map – (see attachment)

b. Apply for a FREE Energy Audit from your local utility provider.  They can provide you with the current R values in your home and other ways to save energy.  Some utilities companies even have a program to help finance the cost to have the additional insulation added. Everyone saves.


Ensure you attic is properly ventilated

a. Check your attic for the proper ventilation air flow.  This is the amount of air and humidity that enters into your attic and exits.

b. Proper ventilation will help will keep your attic temperatures and moisture down.   This will reduce heating and cooling bills.

c. Proper ventilation will contribute to allowing your primary roof to reach it’s warranty life or possibly beyond.

A typical North American ventilated attic  

Cold Air Attic


All data and information appearing on this site is anecdotal in nature, reflecting the contributor’s personal experience and not fact-based research and, therefore, to be used for information purposes only. Read full disclaimer