Ice & water shield offers added leak protection for sloped roofs in climates subject to ice dams and wind-driven rain. It is applied to the roof deck prior to the application of the finished roof covering, used in conjunction with roof underlayment. The membrane seals around nails and roof discontinuities, so water that doesn’t drain properly cannot penetrate the roof. It also creates a weather-tight barrier against wind-dirven rains that can cause shingles to lift and leak. Ice and water shield is typically installed throughout the length of valleys, around penetrations, dormers, chimneys, end-walls, and at eaves. M1 Roofing includes the use of ice and water shield in roof replacement quotes. Be sure that your roofing contractor is, in fact, making of this roofing material.