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A hip rafter is a structural component used to frame certain types of roof designs. Unlike common roof rafters, which run perpendicular to the peak of the roof, a hip rafter connects to the ridge at a 45-degree angle. These rafters can be created out of lumber using traditional stick-framing techniques, or may be included in a pre-engineered steel or wooden truss system.
The most common roof design in much of the developed world is the gable roof. When viewed from the side, this roof resembles an upside down letter V, or a basic pup tent. The roof extends above the front and back of the house, forming a two-sided roof. On the two sides of the home, the siding or wall finishes extend all the way up to the roof's peak, or ridge.
A hip roof, on the other hand, is a four-sided roof design. On each of the four sides of the home, the roof material is visible. The base of the roof and the home siding meet at the eaves, which are at the same elevation all the way around the structure. While a gable roof does not require hip rafters, a hip roof does incorporate these components.
To frame a hip roof, builders start by laying out the ridge beam, which is the peak of the roof. Common rafters extend off the ridge beam at a 90-degree angle on both the front and back of the home. A hip rafter connects to the ridge beam at a 45-degree angle. The standard hip roof requires four hip rafter beams. Smaller beams called hip jacks frame out the two ends of the roof between the hip rafters.
A hip rafter may also be used on more complex roof designs. While the size and configuration of ridge and common rafters is fairly standard, hip rafter requirements can be more complicated. Even with a roof of standard size and layout, the use of hip rafter framing often requires elaborate calculations to ensure the beams are the right size and strength. Historically, carpenters relied on a tool known as a steel square, or roofing square to determine hip rafter sizing. Today, builders often use charts or software programs to size these beams.
Like all rafters, the hip rafter can be fastened to the adjoining framing members using nails or screws. Depending on the roof design, installers may also add metal plates along the joints between the ridge and hip rafters. These plates are particularly useful in areas subject to high wind or hurricanes, as they can help to improve the overall stability of the structure.