Hip roofs boost curb appeal on otherwise boring roof lines. However, they are more complicated to frame than gable ends. There are a handful of rafter tables available to simplify some of the math.
Measure the length of your ridge board. Do this by subtracting the width of your building from the length. A building 25 feet long by 20 feet wide requires a 5 foot ridge.
Cut the common rafters the same as you would for a gable roof. Calculate their length using the roof pitch and width of the building. Remember to measure from the seat cut and subtract half the width of the ridge board. The seat cut is a small, 90-degree section taken from the rafter where it sits on the wall. This guarantees more surface contact between the rafter and the wall.
Nail a common rafter to one side of the ridge board at each end. Raise the ridge and nail common rafters to the other side, opposite the original two. This will hold the ridge in place while you proceed.
Lock the ridge in place by installing the rest of the common rafters. Start in the center of the ridge to ensure it's straight.
Calculate the length of the hip rafter. It will run from the corner of the building to the ridge at a 45-degree angle. Look at the chart on your framing square for a quick reference. Or, find the length by using the Pythagorean theorem. Remember to cut it at a 45-degree angle on both sides where it meets the ridge.
Run a string line down the center of your hip rafter. Attach one end of the string where the hip meets the ridge and the other right above where the hip meets the wall. This guarantees that the hip stays straight as you install the jack rafters.
Use a rafter table to determine the length of the jack rafters. Install them on layout, as you would for common rafters. Check the string line on the hip as you nail the jack rafters in place. Adjust the pressure each jack rafter places on the hip to ensure it doesn't warp or bow to either side. Repeat this process for every corner of the building.
This article assumes you are familiar with framing gable roofs. Use it to extend your knowledge of roof framing to hip roofs as well. Always make sure your rafters are on layout and your hips are straight.