Materials / Ice and Water Barrier
Ice and Water Barrier
accessoryA self-adhering, polymer-modified bituminous sheet installed at roof eaves, valleys, and other vulnerable areas to stop water intrusion from ice-dam backup on steep-slope roofs. The membrane's rubberized asphalt underside bonds directly to the deck and seals around fastener penetrations, giving continuous protection that ordinary felt underlayment cannot. IRC Section R905.1.2 permits it as an alternative to two cemented layers of underlayment in areas with a history of ice damming, requiring that the sheet comply with ASTM D1970. It is used under asphalt shingles, wood shakes, slate, and metal roof shingles on steep-slope assemblies.
Category family
accessory
Slope suitability
steep
Pros
- seals around nail penetrations for continuous waterproofing
- stops ice-dam backup at eaves and valleys where leaks concentrate
- satisfies IRC R905.1.2 as an alternative to double-layer cemented underlayment
- bonds directly to the deck for wind and wind-driven-rain resistance
Cons
- adds material cost compared to standard felt underlayment
- can be difficult to reposition once adhered to the deck
- some formulations require minimum application temperatures
Where code requires this
Related guides
Sources
- up.codes verified 2026-07-28