How to Add the Tail on a Hip Roof

Divide the rise of the roof by the run. In other words, divide the distance from the bottom of the lower frame to the top of the ridge board, by the distance from the middle of the roof to the outer edge of the lower frame. Take the inverse tangent of the result using a trigonometric calculator. This result is the slope of the roof. For example, if your rise is 6 feet and your run is 20 feet, your slope is tan^-1(6/20)=18.4 degrees.

Subtract the slope of the roof from 90. The result is the angle of the plumb cut you need to make for the tail. In this example, the plumb cut would be 90-18.4, or 71.6 degrees.

Lay one of the hip rafters flat. Set the protractor on the lower left corner of the rafter. The bottom of the protractor should lie along the long side of the board. Mark a line on the board at the plumb cut angle that you calculated.

Cut the board along the plumb line. You now have the rafter cut at an angle, so when the hip rafter is put in place, the tail end of the rafter will be vertical, or plumb.
Measure the width of the hip rafter. Draw a line parallel to the tail, as distant from it as half the width of the rafter. Do the same on the other side.

Make a mark in the middle of the short side of the tail, at the top. Draw one line from this point to the top of the line on the right side. Draw another line from the mark to the top of the line on the left side. You now have a triangular shape marked out on the tail end of the hip rafter.

Position a saw on one of these lines and cut straight down. Repeat this procedure for the other side. The tail end will now be cut into a wedge shape, or bevel cut.