Sealants are rarely used on barn roofs because the roof slopes are typically steep enough that rain and snow drain off in true watershed fashion. But house roofs, with dormers, hips, valleys, chimneys, skylights, and plumbing vent penetrations, put more demands on metal roofs. On houses, building a "watertight" roof by sealing all joints, side seams, and endlaps in a metal roof is critical for preventing leaks.

Thermal movement, freeze-thaw cycling, and exposure to ultraviolet light will degrade even the best quality sealants. There are two types of sealants used for metal roofs - tapes and gun-grade. Tapes are preferred to gun-grade sealants because they have a high solids content (about 97%) and don't shrink. Most tapes for metal panels are butyl...

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