Things You'll Need
Nails, 3 1/2 inches long
A hip roof has four slanted sides, unlike a gable roof that is shaped like a tent and has only two sides. A pyramid hip roof is built on a square building, with four triangular sides that meet at a point at the top. A pyramid hip roof differs from the more common hip roofs that are built on top of rectangular buildings because it has no ridge beam, only a point.
Pick the pitch of the roof you are building. The pitch is the number of vertical inches that a roof descends over the span of 12 horizontal inches. A 45-degree roof has a 12/12 pitch, because it drops 12 vertical inches over 12 horizontal inches. The pitch of the roof determines the length of hip rafters that you need, which are the four corner rafters that define the corners of the roof.
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Cut the four hip rafters at a 45 degree angle for a 12/12 pitch roof. Cut bird's mouths at the bottoms of the hip rafters. A bird's mouth is the notch at the bottom of a rafter that fits over the top of the wall.
Install two opposite hip rafters to lean against each other and extend to diagonally opposite corners of the roof. Secure the two hip rafters by nailing them together at their top ends and nailing them to the top of the wall at the bottom ends,. Use 3 1/2-inch-long nails.
Install the second pair of hip rafters to butt up against the top joint of the first two hip rafters. The second two each need to be cut 3/4 inch shorter to accommodate for the thickness of the first two hip rafters on which they are leaning.
Install the rest of the rafters to extend from the sides of the hip rafters down to the tops of the walls. Unlike the hip rafters, the rest of the rafters are installed at a 90-degree angle to the walls.
The result, if you are looking down at it from above, is a central X formed by the four hip rafters, with filler rafters extending from the hip rafters at a 45-degree angle from the hip rafters and a 90-degree angle from the wall where they are attached.