As we've learned ice dams can be a serious problem because of the damage they cause. Wet insulation, rotted wood, mold in attic, mildew on drywall, damaged floors and damaged shingles are just some of the damage that can occur. A proper roof installation will help insure that snow melt-off or even rain that forms behind an ice dam will not leak into the house. A shingle roof is designed to channel water from the higher points to the lower sections where it will exit the roof either into a gutter system or flow directly to the ground. Shingle roofs are not designed to hold water or prevent water from flowing upwards on the roof.
Ice And Water Shield
Ice and water shield (or water and ice shield) is a waterproof water barrier that is placed directly over the roof sheathing. It will prevent water from saturating the roof sheathing if water does get behind the shingles. Water and ice shield is self-adhesive and will stick to the sheathing and comes in 3 foot widths. In most cases one course of the water barrier is not sufficient. Overlap the first course with another course to extend the protection further up the roof. In combating ice dams it is very important that the first course of the water barrier extends down over the edge of the roof and goes behind the gutter. This will seal the junction where the roof sheathing and fascia meet and where water can get in during the formation of ice dams. Please note that any edge metal (drip edge, gutter apron, etc.) should go over the ice and water shield in the colder snowy north. Then install the roof shingles over the water barrier.
Roof Flashing
A leaking roof can be caused by the improper installation of roof flashing. Roof flashing can be copper flashing, aluminum flashing or some other type of metal flashing and is installed after the water barrier has been applied. Flashing installation works in conjunction with shingle installation. This can be wall flashing (known as step flashing) that is also used when flashing a chimney. Chimneys use a combination of step flashing and counter-flashing to provide a watertight seal.
Another type of metal flashing is placed in the valley area of the roof and is called valley flashing. Before installing the valley flashing a course of the water barrier should be applied to the sheathing the whole length of the valley. If the pitch of the roof is low, lapping another course on each side of the first course may be required. Then place the valley flashing on top of the ice and water shield and secure it with nails. It is important that the nails are placed only on the extreme outside edge of the valley. Often a leak in a valley can be traced to a nail hole(s) close to the middle of the valley. This hole may provide an entry point for water to enter the house if an ice dam forms in the valley.
Always remember to purchase quality products for your roof. Proper installation of ice and water shield, roof flashing and shingles will prevent most ice dams from causing roof leaks.
Monday, November 16, 2009
Saturday, November 14, 2009
ICE DAMS - Causes, Removal, Damage, Prevention
Icicles hanging from a roof may look pretty but they may be an indication of ice dams forming on the roof. Ignoring them will not minimize the fact that the ice and water may be causing significant damage to the house.
Ice Dam Causes
When snow accumulates on a roof a cycle of melting and refreezing occurs. The snow melt will refreeze at the cooler edge of the roof and create a ridge of ice commonly called an ice dam. These dams will block water from escaping off the roof by creating a pool of water. This water can sometimes leak into the soffit area or leak back under roof shingles and into the house creating damage to ceilings, walls, insulation, cabinets, flooring, and other personal belongings. The warmer the attic the greater will be the amount of water from snow melt. Though it is not always possible or even practical, one way to stop snow melt is to remove all the snow with the use of a snow roof rake.
Ice Dam Removal
Removing ice dams off a roof can be very dangerous. Snow covered roofs can be very slippery. Ladders can fall over because of slippery ground and ice on the gutter. In addition, damage can occur to the roof while removing ice. Immediate ice removal will however quickly stop the water coming into the house. This can be accomplished by chipping a channel into the ice dam to release the trapped water. Another way is filling a sock with one of the appropriate ice melt products and placing it on the ice dam to melt a groove through the ice that will allow the water to run off the edge of the roof. Ice melt products may be harmful to the shingles or they may damage plants, read the packaging material carefully!
Ice Dam Damage
Roof shingles and gutters can be damaged by the ice dams. Any wood that has become saturated with water is subject to wood rot. The wet wood can also provide perfect conditions for the development and growth of attic mold (sometimes called black mold) or mildew. Mold and/or mildew can grow in the attic, in damp wall cavities or grow on wet drywall. Wet insulation can also harbor mold. Mold removal can be very difficult as well as quite expensive.
The water running into the house can also damage walls, floors and floor coverings, cabinets and wood trim used around doors, windows, baseboards and ceilings.
Ice Dam Prevention
Ice dam prevention begins in the attic. Since attic heat is a major contributor to the melting of snow on the roof and subsequently to the formation of ice dams, lowering the temperature should decrease the formation of ice on the roof. There are 2 partners in this endeavor to prevent ice dams; attic insulation and attic ventilation. The proper amount of attic insulation, combined with sealing all areas that may leak warm air into the attic, will help keep the attic cooler while sufficient attic ventilation will allow the warm air that does collect in the attic to be replaced with cooler outside air.
There are also some steps to be taken during roof installation that will help prevent ice dams but that will be the topic of another post.
Ice Dam CausesWhen snow accumulates on a roof a cycle of melting and refreezing occurs. The snow melt will refreeze at the cooler edge of the roof and create a ridge of ice commonly called an ice dam. These dams will block water from escaping off the roof by creating a pool of water. This water can sometimes leak into the soffit area or leak back under roof shingles and into the house creating damage to ceilings, walls, insulation, cabinets, flooring, and other personal belongings. The warmer the attic the greater will be the amount of water from snow melt. Though it is not always possible or even practical, one way to stop snow melt is to remove all the snow with the use of a snow roof rake.
Ice Dam Removal
Removing ice dams off a roof can be very dangerous. Snow covered roofs can be very slippery. Ladders can fall over because of slippery ground and ice on the gutter. In addition, damage can occur to the roof while removing ice. Immediate ice removal will however quickly stop the water coming into the house. This can be accomplished by chipping a channel into the ice dam to release the trapped water. Another way is filling a sock with one of the appropriate ice melt products and placing it on the ice dam to melt a groove through the ice that will allow the water to run off the edge of the roof. Ice melt products may be harmful to the shingles or they may damage plants, read the packaging material carefully!
Ice Dam Damage
Roof shingles and gutters can be damaged by the ice dams. Any wood that has become saturated with water is subject to wood rot. The wet wood can also provide perfect conditions for the development and growth of attic mold (sometimes called black mold) or mildew. Mold and/or mildew can grow in the attic, in damp wall cavities or grow on wet drywall. Wet insulation can also harbor mold. Mold removal can be very difficult as well as quite expensive.
The water running into the house can also damage walls, floors and floor coverings, cabinets and wood trim used around doors, windows, baseboards and ceilings.
Ice Dam Prevention
Ice dam prevention begins in the attic. Since attic heat is a major contributor to the melting of snow on the roof and subsequently to the formation of ice dams, lowering the temperature should decrease the formation of ice on the roof. There are 2 partners in this endeavor to prevent ice dams; attic insulation and attic ventilation. The proper amount of attic insulation, combined with sealing all areas that may leak warm air into the attic, will help keep the attic cooler while sufficient attic ventilation will allow the warm air that does collect in the attic to be replaced with cooler outside air.
There are also some steps to be taken during roof installation that will help prevent ice dams but that will be the topic of another post.
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