Waterproof Roofing Underlayment on Steep-Slope Roofs

March 30, 2014
Publication: Architectural Roofing & Waterproofing
Author(s): Scott Tomlinson

Ice dam-related water leakage continues to plague many steep-slope roofs. Some contractors and consultants we meet while evaluating leakage from ice dams suggest that the water leakage occurs due to material and design limitations, not the roofing installation. Regardless of design and construction, ice dams can form under the right conditions, although the risk can be small at a well designed and constructed roof (i.e., design and construction beyond the minimum code requirements). All roofs in cold regions have a risk of ice dam formation; therefore, roofs must be constructed to resist water leakage from snow, ice and water buildup behind ice dams. Nearly all roofs can be designed and constructed to prevent water leakage from ice dams. In our experience, roofs that leak when ice dams are present typically leak due to basic design and construction errors. This article focuses on constructing a waterproof roof to prevent water leakage that results from the formation of ice dams. We provide a brief review of ice dam formation; discuss codes and standards related to ice dam protection; and explore design and construction considerations. We do not discuss the important topic of heat loss and ventilation required to minimize the risk of ice dam formation