How-to-install-gambrel-metal-roof, metal is one of the longest lasting roofing materials available. a well-installed and maintained metal roof can last a half-century or more. a gambrel, or barn roof, is similar in style to a gable roof, with one exception. about half-way down the roof, the pitch changes from the initial gentle slope to a steeper slope, designed to shed rain and .... Installing metal roof on gambrel barn. on my farm i have an old barn with a gambrel roof. the metal is in bad condition and needs replacing. the eave is about 40 ft. high and i am trying to figure out a safe way to do the work myself.