PREVENTING ICE DAMS-It Starts At Roof Installation

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.