With its long tradition as a garden structure, a free-standing gazebo makes a fine addition to an outdoor living space. There’s no rule that says that a gazebo has to have eight sides, but octagons are eye-pleasing shapes that are relatively straightforward to frame.
In a previous article (“Framing Square Basics: Octagon Layout,” Nov/Dec/22), I demonstrated how to use a framing square and dividers to lay out octagons measuring less than 67 inches wide. For larger octagons—a gazebo or a turret, for example—knowing that the length of one-half of one of the sides can be determined by multiplying the octagon’s width by .2071 and that all of the angles are 45° or its complement simplifies the layout. Following the example in that article, the sides of a 12-foot-wide octagon will measure (.2071 x 12 feet) x 2 = 59 5/8 inches.
Framing the roof for an octagonal structure is a little more complex. If you ever have to build an octagonal roof, I recommend that you start by fabricating an octagonal ridge block or, perhaps, an eight-sided king post that extends down to the floor or to a beam at ceiling height. The first eight rafters, which are common rafters, will bear on the eight flat sides on the ridge block or king post. To avoid an awkward cut on the next eight rafters, which will be hip rafters, it’s imperative to make the flat sides the same width as the rafter material.
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