What Are Rafters in Construction?

March 8, 2024

Rafters are a critical component of any building’s roof, providing support for both the roof covering and any additional weight that may be imposed on it. The rafters themselves are made of wood, often in conjunction with other structural elements like joists and ceiling girders. The exact materials used depend on environmental factors like climate conditions and local natural resources.

Depending on the roof’s pitch, rafters can be steeply or flatter angled to create different architectural styles. In addition, they can also be exposed or concealed to meet various aesthetic preferences for the interior and exterior of a building.

There are several types of rafters, including principal and common rafters, purlins, and hip rafters. Principal rafters are larger than common rafters and help to distribute the load of the roof across the structure. Auxiliary rafters are smaller rafters that support the principal rafters above them. Hip rafters extend from the wall plate and land at the ridge board, helping to form a hip in the roof.

While rafters are the traditional way to frame a roof, trusses are an alternative that offers many benefits. Rafters are traditionally constructed on-site and then connected to the exterior walls using ceiling joists. They can be left exposed for a rustic or contemporary look or they can be covered with insulation and drywall for a more traditional design. They can also be built to accommodate a vaulted or pitched ceiling. They don’t require as much front-loaded planning as trusses, which can be beneficial for construction projects in remote locations or in situations where the schedule is tight.

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