Once climbing flowers are established, the arbor will be an eye-catching, softening feature. The overhead arch, cut from 2x8s, is easier to build than it might look. And with 4x4s as the primary framing members, the arbor has a substantial appearance.
Choose lumber that will stand up to your weather conditions. (Remember that if you are going to have plants climbing over the structure, they will tend to hold moisture on the arbor.) If you plan to treat or paint the arbor, consider doing so before you build -- painting the crosspieces in place is difficult and time-consuming. In addition to basic carpentry tools, rent a heavy-duty saber saw for cutting the curved pieces. You will need to enlist a helper to assemble the arches.
1. Draw template. On a large piece of cardboard, draw a template for your arches, using a compass made from a nail, a string, and a pencil. Using a framing square and protractor, divide the arch into four equal sections and cut out the four arches.
2. Cut arches. On the 2x8, use the cardboard pieces to mark for your arch members. Cut them out with a jig saw. Temporarily attach your arches together with 3x3/4-inch mending plates. (You will remove them after the arbor is assembled.)
3. Sink posts. Dig the postholes below the frost line and shovel a little gravel into the bottom of each. Set the posts in and temporarily brace them into position, checking for plumb in all directions. Starting with one post, mark a point 7 feet above the ground. Level across to the other posts and mark them. Use a square to draw a line around each post, and cut it with a hand saw or circular saw.
4. Add framing. Attach 2x4 horizontal braces to the top of the posts, leaving 1-1/2 inches of space at each end for the arches. Position the arches, then attach the 4x4 horizontal braces, cut to the same length as the horizontal 2x4 braces. Install the crosspieces, using a scrap of 1x3 as a spacer. Once everything is in place, gradually fill the holes and tamp the posts in place.