A girder truss is a type of secondary roof support that is most commonly used in the construction of buildings that have a roof that is irregularly shaped. Its main function is to support the weight of the roof.
A girder truss is typically present in L- or T-shaped buildings due to the fact that the roof changes direction at a sharp angle. Typically, a girder truss is constructed of wood, although stronger materials, such as steel, are often used. A secondary function of a girder truss is to provide structural support to both the roof and the adjoining walls and help buildings withstand hurricanes and other powerful forces.