Building an arch is one of the easiest ways to give your landscape a striking centerpiece. And this arch is easier than most. Made from just six parts, it can be built in less than a day—even if you're a rookie carpenter. The design is versatile, too: The arch can become a gateway in a fence, frame a walkway through a hedge or stand alone in your yard or garden. You can stain it for a rustic look or paint it for a more formal look.
The arch in this article was built from rough-sawn cedar, but it can also be built from pressure-treated lumber for about half the cost. Depending on where you live, you may have other choices of rot-resistant lumber available, such as cypress or redwood. If you choose treated lumber, you'll find everything you need for this project at home centers. If you choose another wood species, you may have to special-order lumber or visit a traditional lumberyard.
You'll need only standard tools like a drill, a circular saw and a jigsaw. Make sure your framing square is a standard model (16 x 24 in., with a longer leg that's 2 in. wide). If yours is an oddball, buy a standard version so you can easily mark out the brackets (see Photo 2). A few days before you dig the postholes, call 811 to have underground utility lines marked.
To get started, cut notches in the tops of the beams (Photo 1). If you're using “rough-sawn” lumber as we did, you may have to change the length and depth of these notches to suit your 2x8 headers. (The dimensions of rough-sawn lumber vary.) Set the cutting depth of your circular saw to 1-1/2 in. to make the crosscuts for the notches. Then set your saw to full depth to make the other cuts.
Next cut the 2x8 headers to length and mark arcs at the ends as shown in Figure A. To mark the curves, use the bottom of a 5-gallon bucket or any circle that's 10 to 11 in. in diameter. Cut the curves with a jigsaw.
The curved brackets may look complicated, but they're easy to mark out since they're based on a standard framing square. After marking with the square (Photo 2), set a nail in your sawhorse 20 in. from the edge of the board. Carefully adjust the position of the board until both corner marks of the bracket are 24 in. from the nail. Then, holding your pencil at the 24-in. mark on the tape, draw an arc. To draw the second arc, move your pencil to the 29-in. mark on the tape (Photo 3). Cut the straight edges of the brackets with a circular saw and the arcs with a jigsaw. If the curves turn out a bit wavy, smooth them with an orbital or belt sander. Don't be too fussy, though. Nobody will notice small imperfections.
Mark one header 12 in. from both ends and lay out the posts, aligned with the marks. Take measurements at the other end to make sure the posts are perfectly parallel. Drive 3-1/2-in. screws through the posts and into the header. At the tops of the brackets, drive 3-in. screws at a slight angle so they won't poke through the face of the header (Photo 4). Set 1-1/2-in.-thick blocks under the other ends of the brackets. Then drive screws at an angle through the sides of the brackets and into the posts. Be sure to drill 1/8-in. pilot holes so you don't split the brackets. Set the second header in place and screw it to the posts. Note: The brackets are not centered on the posts, so there's a 1-in. gap between the second header and the brackets.
You'll set the arch posts into 10-in.-diameter holes 30 in. deep. But before you move the arch into place, screw on a temporary 2x4 “stretcher” 30 in. from the post bottoms. Then round up a helper or two and set the posts into the holes. Patiently level and plumb the arch, using stakes and 2x4s to brace it (Photo 5). Be careful not to nudge the posts out of position as you fill the holes with concrete. Let the concrete harden for at least four hours before you finish the wood. We brushed on two coats of clear penetrating wood finish to deepen the color of the wood and repel moisture.