GAF WEATHERWATCH 36 in x 50 ft 150 sq ft Polypropylene Roof Underlayment 18x18 Tile A: The tiles are 1 8 in 314846561 A: The tiles are 1 8 in thick fatigue reducing grip for long drywall finishing sessions Looks better: fiberglass reinforcement helps resist wrinkling buckling and lies flat under Shingles Protection against ice dams is required wherever the January average temperature is 25 ° F or lower or where there is a possibility of ice forming in the eaves (check local building codes for specifications in your area) Dependable: self seals around nails or metal roofing fasteners Saves labor: dual side selvage and split back release film help reduce labor Available in 1