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.    Read more.