A gambrel truss is a type of roof support. It is generally characterized by two slopes on either side of the peak. This type of truss is often used to make the roofs of barns, hangars, sheds and homes with a Colonial design. Gambrel trusses function by transferring the weight of a roof to the structure's walls, and they offer more floor and head space than some trusses. There are many advantages — and some disadvantages — to using a gambrel truss, as well as different materials that can be used.
The purpose of a gambrel truss is most often to provide support for a roof. Their spacious design means gambrel trusses are often used in larger buildings, such as barns, that can benefit from the extra space. Small sheds also can benefit from this kind of roofing. Many buildings incorporate the gambrel design because of its general characteristics.
Often symmetrical, a gambrel truss incorporates two slopes. The higher slope is generally flatter than the lower slope, which opens up the interior space while still providing protection from the weather. Gambrel trusses, like many other trusses, take advantage of the geometric strength of triangles to distribute the roof weight to the walls of the building, which often alleviates the need for interior supports. Angles are generally adjusted to the width and height of a building to provide maximum strength and durability.
In addition to barns and other storage buildings, a gambrel truss also might be used in some homes. This kind of design has been utilized since Colonial times and may still be used to create a classic style while also providing a little extra room. Many older homes also might incorporate some version of a gambrel roof. The general popularity of this design can be considered an indication of its many advantages and few disadvantages.
The slope design is generally strong against harsh weather conditions. The amount of surface area and the angles can deflect water, snow, ice and other damaging weather patterns for many years. Especially in storage buildings such as hangars and sheds, the extra head space also is an important advantage. As with many building featuring spacious interiors, a building using gambrel trusses may be harder to heat and cool. For many buildings that incorporate a gambrel truss, however, this might not be an issue.
Wood, metal and composites can all be used to create gambrel trusses. Metal connectors are usually used to provide maximum connective support between truss members. Depending on the size and materials used, a gambrel truss can be heavy, which means it may require a crane or other heavy-duty machine to lift it into position.