Ice Dam

Ice-dam membrane should be the first row of roofing-felt underlayment. The membrane is an adhesive-backed, rubberized product that seals against leaks near the eaves due to ice dams. A 36-in.-wide roll that covers 100 sq. ft. costs about $36.

Because of the membrane's adhesive back, it must be aligned properly as it's rolled out. Peel the plastic adhesive backing from the first 2 ft. of the roll, then start it along the gutter apron with about a 1/4-in. overhang at the edge. Check that the membrane is aligned. Then roll it out, peeling away the plastic backing as you go.