A gambrel roof consists of twin slopes (one steeper than the other) with a gabled structure at both ends. It's simple and stylish structure is preferred by architects because the design is minimalistic with few complex structures required for building it. A gambrel roof is also the most common form of roofing preferred for building detached structures like barns.
A gambrel roof can be used to create extra space in a large room used for storage purposes. If you have seen a barn from the inside, you would have noticed that the gambrel roof adds a virtual floor inside the building without requiring an extensive frame to hold it in place.
City dwellers can use the gambrel roof to add extra space to their single-storied detached structures in their garages so that the extra space can be put to good use for storing tools. The space carved out by building a gambrel roof can be even used a mini workshop with a small worktable.