Before installing shingles on a roof, a layer of underlayment — felt paper or tar paper — must be placed. This underlayment gives your roof an extra later of protection against small bits of water that can get under the shingles to reach the wood deck.
To provide even greater protection against water damage, a special type of underlayment called ice and water shield can be used around the lower edge of the roof deck, or anywhere that leaks are common. Ice and water shield is a rubber-like asphalt and fiberglass membrane that is applied at the gutter line, in the valleys, around chimneys, skylights and any other areas of the roof that benefit from a leak barrier.
Ice and water shield is especially important in areas where ice can form near the eaves, causing water to back up under the shingles.
Ice and water shields can also benefit low slope roofs because they are more susceptible to water damage due to high winds.
Felt paper is nailed in place, but ice and water shield has a sticky backing, which holds it firmly in place when it is backed against the dry wood deck. This adhesive helps prevent snow and ice roof damage.
When felt paper is nailed into place, it creates a hole, which is sensitive to leaks. Ice and water shield’s flexible, rubbery shape forms a tight seal around roofing nails, so even if water backs up under you shingles, ice and water shield will prevent it from leaking into your home.
Used for waterprofing under shingled roofs to prevent water penetration due to ice dams and wind-driven rain. It is also used as an underlayment around chimneys, dormers, vent stacks, skylights, and other roof structures.
Ice Dams – form when melted snow runs down the roof to the cooler eaves and re-freezes. Water collecting above the dam works its way underneath the shingles and may penetrate through the roof deck.
Wind-Driven Rain – wind propels rain under the shingles and may penetrate the roof deck. Low slope roofs are most susceptible to this condition.
- Ice and Water Shield protects against water leakage due to ice dams