A Hip Roof Framing Guide

Geometry

• The framing of a hip roof begins with the construction of the four hip rafters and the ridge beam. If the roof is going on top of a square building, there won't be a ridge beam because all the sides will meet at a point at the top. On top of a rectangle, there will be a ridge beam that runs parallel to the two longer sides. The shape and size of the desired roof sections need to be worked out on paper before construction begins, or the framers may be in for unexpected surprises in the middle of construction.

Pitch

• Roof pitch determines the size of the rafters and the look of the completed roof. Roof pitch refers to the steepness of the roof, expressed in building terms as the number of vertical inches that a roof drops over a span of 12 horizontal inches. A roof that descends 6 inches over 12 horizontal inches is referred to as having a 6/12 pitch. When designing a hip roof, you will make the construction process much simpler if you assign the same pitch to all four sides of the roof. While it is possible to vary them, this creates very complicated framing situations.

Strength

• The design of a hip roof provides advantages in situations with high winds. Because there are no exposed gable ends, a hip roof is more impervious to dangerous winds because the winds tend to flow over it rather than run into it. When framing a hip roof, you can increase its resistance to high winds even further by incorporating rafter braces and collar ties into the design. Rafter braces secure the hip rafters to the ceiling joists underneath. Collar ties are metal strips that are wrapped around the bases of the rafters and secured to the ends of the joists.

Design

• Designing the framing for a hip roof involves some simple geometry that allows you to determine the lengths of the lumber that you will need. You can get an overview of your hip roof design by drawing a top view, but you will need to take the pitch of the roof into account when determining how long the rafters will be. A hip rafter that runs at a 6/12 pitch over a span of 10 feet will be longer than 10 feet because of the rise involved. Knowing all of these measurements before you start building lets you minimize waste and be more efficient in your resource use.