Ice Dam: A Natural Phenomena That Forms on Roofs

What is an ice dam? Unless you've lived a while in a colder climate, chances are you have never heard of an ice dam. Whether you've heard of an ice dam or not, it's quite likely you've seen one on a roof if you live in a cooler climate. It's important to note that an 'ice dam' is a natural phenomena (not man made). The following illustration illustrates an ice dam.

Effectively, snow and ice build up along the edges of a roof creating an area that restricts water from flowing off your roof, effectively creating some 'ponding'. Ponding is an area on your roof where water cannot escape, and especially after extended periods of time, on most roof substrates this will prevent a leak. This naturally forming phenomena is nearly impossible to stop, unless some preventative measures are taken.

Ice Dam: A Short Definition

In short, an ice dam is simply a 'dam' created by ice and snow which prevents water from flowing off a roof, which can eventually lead to leaks and other problems, especially with shingles, tile, slate, shakes or other similar roofing materials.

Here's an example of an ice dam

Notice the parts of the roof where the snow has melted. These are areas with either increased airflow (from out of the home) or with poor insulation (a place where heat is escaping).

Ice dams can be mostly prevented with some roof designs and materials. These preventative measures are probably a good idea unless you like the idea of water seeping into your roof and flowing down your walls into your home!

A Roof With a Major Ice Damn Problem

This is an example of a roof with a much more extreme ice dam. You can see that the insulation of the roof is poor, which has melted the snow almost through the center, while the edges of the roof, which stay colder (since they are a few feet away from the home), icicles, ice, and snow have slowly built from the runoff.

An ice dam like this becomes an emergency if it is causing water to flow into a home. The only immediate fix is to remove the ice. Avoid going up on top of an icy roof, this is quite a high risk of personal injury (if you slide and fall off). It's probably safer to find a secure location for a ladder, or to use a tool that allows you to reach the roof safely (e.g. a roofrake). Care must be taken not to damage the roof.

When Do Ice Dams Form

In colder northern climates homes are more at risk for forming ice dams. During extended periods of time while the weather stays substantially below freezing (zero degrees Celsius), parts of the roof melt off snow and ice, while other parts remain frozen. Heavy snow conditions are also ideal for ice dam formation.

Roof Substrates and Materials That are Most at Risk when Ice Dams Form

Spanish tile, shingles, or shake materials roofs are more at risk from damage from ice dams because these types of roofs are based on the assumption that rain and melting snow will slide right off the roof. When an ice dam forms, the water can no longer flow off the roof, so following the path of least resistance, the water can flow right into your home or business!

Preventative Measures

Ok so now that it's clear Ice dams are harmful, you may be asking what you can do in terms of preventative measures. The best prevention is good insulation in the attic. This will prevent heat from escaping your home, so that the roof will not heat or cool unevenly (the real core cause of ice dams). Another preventative measure is to prevent air from escaping through your roof.

If good insulation or preventing airflow is not viable for your roof, or if it's not sufficient to prevent ice dams from forming, there are a few other options. In the case of an extreme emergency, you can remove the ice & snow from the roof on your own. Care must be taken not to damage the roof, tiles, and drains. Broken drainage systems can lead to leaky roofs (the same net effect as an ice dam--trapped water flows to a new path of least resistance, which could be right through your roof, up under tiles, or shingles into your home).

The Best Solution for Ice Dam Roof Problems

A roof contractor can install an impermeable plastic membrane along the edge of your shake, tile, or shingle roof. The idea here is simple. Your roof will be completely waterproof from the gutter, up a portion of your roof (most likely a few feet, although this will vary with roof design, and area of the country). Effectively, this wont prevent ice dams at all. However, it will prevent an ice dam from creating roof leads. So what if the contractor installed the ice dam and your roof still leaks? Assuming your roof is free of gutter, drainage, and other problems, it's possible the membrane was not installed high enough up past the roofline, or it's also possible the contractor installed the membrane incorrectly, and you're now suffering the consequences.

Summary: If a contractor asks if you want "ice dam protection", it's probably worth it if you're in a colder climate area.

In summary, Ice dams create leaks, and ice dam protection is just a plastic waterproof membrane that goes under a roof and prevents leaks.

Find a local Roofing Company.