One of the most common causes of roof leaks is a condition called ice damming. Ice damming occurs in the winter months when ice forms and builds up on the roof. The most common areas of ice build up are at the eaves and in the valley areas but are not limited to these areas. In some cases the ice can be several inches thick and can extend several feet up the roof from the eaves, also the ice can become icicles that can grow to become dangerous.
When the ice forms on the roof it can block the natural flow of rain water or melting snow and force it through the roofing materials and into the building. This condition is called ice damming and can cause a great deal of damage to a home’s interior as well as the dangers of falling ice to people and property. The only way to stop an ice dam leak once it has started is to remove the ice and snow from the areas where the leak is occurring. This can be very difficult as they almost always occur during bad winter conditions when it can dangerous to go up on the roof.
One of the preventative measures we use to stop water from entering the building’s interior from ice damming is a waterproofing membrane being installed on the roof deck before the shingles or other roofing materials are installed, this membrane is commonly called ice and water shield. The membrane is installed generally in those areas that are prone to ice build up such as the first 3-6 feet up from the eaves and in the valley areas. Once these materials are installed they will form a watertight barrier to stop any moisture that can be forced through the finished roofing. This in most cases will stop water from entering the building. This however will not stop the ice dam from forming.
In order to stop the ice dam from forming on the roof you must correct the root cause, that is a build up of heat in the buildings attic. In the winter months a heated home will transfer heat into the attic from a building’s interior through inadequate insulation, unsealed light fixtures or other sources such as bathroom or kitchen exhaust fans that are not vented correctly. This excess heat can begin to build up so that the inside of the attic space becomes warm enough to melt the snow that is on the roof. If this occurs when the outside temperatures are below freezing the water will run down the roof to the eaves where it will re freeze as it has lost the attic heat source, if this condition is allowed to continue the ice will keep building until the ice dam forms and a leak occurs. This situation occurs usually when there is a lot of snow and an extended period of cold temperatures.
The solution to stopping ice forming in the roof is to ensure that the attics temperature is as close to the outside temperature as possible therefore the only time you have melting snow on your roof is when the outside air is above freezing allowing the water to run away naturally. To do this we must stop the sources of heat in the attic and properly ventilate the attic space. First the insulation must be adequate and all the sources of unwanted heat are sealed and insulated. Secondly the attic space must have an exhaust through roof venting and a source of cooler air intake such as soffit venting. This will allow any unwanted heat and moisture to draw out of the attic allowing it stay cool. The air in the attic will only flow out the roof vents at the top of the roof if the warmer air is replaced with cooler air entering the attic through the soffits or other areas lower down the roof. The square footage of roof vents should match the square footage of soffit venting or intake vents creating balanced airflow. It is very important that the air intake is not blocked by insulation inside the attic, there are various methods used to stop this including the use of pre-manufactured channels called moore vents.
Once the attic space is properly insulated and ventilated the chances of any significant ice buildup will be greatly reduced ,however in some cases the design or shape of a roof or age of the building are going to promote ice build up in these cases as a last resort heating cables may need to be installed.