Laying out an octagon
I need to know how to lay out the foundation piers for an eight-sided gazebo.
Dennis R. Burr, Lumby, None
Dan Daley, a framer in Bend, Oregon, replies: I’d break the octagon down to a cross made up of a large rectangle and two smaller rectangles. When connected, the cross’s eight corners form an octagon. Assuming you have the dimensions of the octagon, those numbers and an architectural scale can be used to learn the size of the large rectangle and the two smaller rectangles that form the cross.
Once you know the dimensions, you can set up eight batter boards for the cross (see drawing). A batter board is simply a pair of 2×3 stakes driven into the ground about 2 ft. apart with a third 2×3 tacked across the stakes. Tie a string to the crosspiece, whose 2-ft. length allows you to adjust the string from side to side. Set up the batter boards outside the vicinity of the gazebo site to allow yourself plenty of working room.
From a fixed point of reference, say the distance from the house to a corner of the gazebo, set up the first pair of batter boards, string a line and adjust it as necessary. Then use this line as a reference point for positioning the rest of the batter boards, following the dimensions of your plans. Then check your strings to make sure they intersect at right angles, and establish a square centered in the cross. Measure along the lines away from the square to each of your eight corners. Mark the dirt and dig the holes.