How to Frame a Raised Hip Roof

Use a measuring tape to determine the house's width. Divide the width in half to determine the horizontal distance a rafter has to travel to meet the rafter coming from the opposite side. From now on, this horizontal distance will be called "Side A."

Measure the length of the house and subtract (Side A × 2) from it. This will give you the ridge board's length: the board on which adjacent rafters will be nailed on later.

Determine the angle of your roof, which is the angle formed by Side A and the rafter. Use a tangent table to determine the tangent of your roof's angle -- from now on this will be referred to as the "Roof Angle." Multiply the tangent by Side A to determine the distance between the middle of Side A and the roof's top.

Raise both sides to the second power and add them to calculate the hypotenuse's -- in this case the rafter's -- length squared. Calculate the hypotenuse's square root and deduct half the ridge board's thickness to determine the "theoretical length" of the rafters you must use for the hip roof. The actual length of the rafters must be up to a foot longer, so that rafters extend beyond the house walls -- this part is called the "tail" -- and forms the soffit.

Add 90 degrees to the Roof Angle and subtract the sum from 180 to calculate the correct angle of your plumb cut: the cut on the meeting end of opposite rafters. Use a radial arm saw to make an accurate angle. Repeat the cut on the opposite end of the rafter, so that the rafter's ends are parallel.

Measure the theoretical length of the rafter with the tape, starting from the plumb cut. When you have reached the theoretical length, form a dot with a marker. Draw a line parallel to the plumb cut -- from now on, this will be referred to as the "Birdsmouth Vertical" or BM.

Measure the house walls' thickness. Divide the wall thickness by Roof Angle tangent and note down the quotient.

Start measuring from the bottom of BM upwards, until you reach the quotient. Mark a spot and draw a line perpendicular to BM, starting from BM and reaching the rafter's bottom side -- from now on, this will be referred to as the "Birdsmouth Horizontal" or "BH." Cut out the right triangle formed by the BM and its perpendicular line to form the birdsmouth.

Draw a line parallel to the BH, starting from a spot of the tail's end. Cut across this line with the miter saw. After the cut, the tail's end and the new side must have the same length.

Use the rafter as a template to make a plumb cut, a birdsmouth and a soffit cut an all rafters of your frame.

Calculate the length of the hips -- the diagonal boards of the hip roof -- and the rafters attached to them using either the calculator by Blocklayer.com. The plumb cut and birdsmouth require precise cutting, otherwise the pieces could be rendered useless for your frame.

Attach the plumb cut ends of a rafter to each end of the ridge board and nail them together. Place the shape across the length of the house and nail the rafters on the middle spot of the side walls.

Build the rest of the frame around the ridge board by adding the remaining rafters and the four hips. Make sure you nail the boards tight to create a sturdy frame.