Trusses are used on about 80 per cent of new houses today. They have largely replaced traditional rafters, which must be cut and built at a house site. Rafters use heavier boards and require more skilful carpentry and installation. Trusses are built in factories using precise cutting and joining equipment. Rafters are nailed together; trusses are fastened with steel plates with long spikes that penetrate the wood. Trusses use lighter lumber but are stronger than rafters because they have more internal support. They are commonly used in gable roofs but also can be used in hip roofs.
Use trusses to simplify construction of a hip roof. A traditional hip roof is framed with a centre rafter from the gable peak to the end wall, side or hip rafters angled from the peak to the corners and "jack" rafters between to connect the centre and hip rafters. These require complex angle cuts on the jack rafters, which vary in length as the roof slope decreases.
Measure the roof and determine the length of the hip from an end wall to the peak of the gable roof. That will vary with the pitch of the roof; the hip pitch matches the gable pitch. A lower pitch will have a longer hip. These measurements are critical for ordering hip trusses.
Study hip roof styles. There are systems called terminal hip, hip master and step down. They vary in the way they are engineered and installed. All eliminate the angle-cut rafters from a centre rafter to the corner rafters. They connect to a girder truss at the top of the hip and slope straight down to the end wall in varying lengths.
Build a Dutch hip roof with special trusses. A Dutch hip slopes to an end wall like a standard hip roof but has a small gable between the end of the roof and the apex. The top or girder truss is a gable truss, with hip and jack trusses bolted to it at the bottom of the gable.