The side panels (A, Fig. A, below) are three-layer sandwiches, with vertical pickets (A1 and A2) held between horizontal rails (A3 through A6). Assembly is easy because the pieces are simply stacked, glued and screwed. The top rail is three layers thick. Its inside rail covers the tops of the pickets to protect the end grain. The other rails are fastened to the outside, so moisture can drain between the pickets. Glue these panels together on a flat surface, so they aren’t twisted. Use waterproof glue.
1. Cut all the pieces to width.
2. Cut the rails and the two outer pickets to length, with the ends squarely cut.
3. Make patterns for the curved profiles in the top rails (Fig. B, below) by swinging arcs on 1/4-in.-thick scrap stock and bandsawing. Use the patterns and reference points A and B to transfer the arcs to the top rail blanks (A3 and A4). Then saw out the rails.
4. Glue and screw the inside top rail to one of the outside rails. Make sure the ends align and the glue joint is tight. Remove any squeezed-out glue.
5. Tack the frame together (Photo 1). The two outer pickets protrude beyond the rails by 3/8 in. to form tongues (Detail 1, below). Draw layout lines on these pickets to indicate the ends of the rails. Lay the pickets on the top and bottom rails. Butt the pickets against the inside top rail and align the other ends with the bottom edge of the bottom rail. Apply glue and tack the corners.
6. Square the frame and then screw it together with 1-1/4-in. deck screws. Drill countersunk pilot holes first, so the screws don’t split the wood. Work fast, so you finish before the glue sets up.
7. Use your layout lines to attach one middle rail to the bottom side of the frame. Make sure its ends align with the top and bottom rails.
8. Install the inner pickets, using 2-1/2-in.-wide spacers (Photo 2). Cut the pickets to length as you go. Fasten them with glue and screws in predrilled holes.
9. Glue and clamp the remaining top, middle and bottom outside rails. Make sure the ends align.
10. Smooth the curve on the top rails using a belt sander or a sanding drum chucked in a drill.
Build the Posts
The posts (B) are hollow, made from four pieces that are simply butted, glued and clamped (Photo 3).
11. Cut the post pieces (B1 through B3) to width and length. The sides are narrower, so butting them between the front and back pieces creates a square post.
12. Glue and clamp the sides to the back piece. Remove any squeezed-out glue.
13. Glue and screw a block (B4) to the back side of the front piece.
14. Glue and clamp the front piece to complete the post; make sure the bottom edges are flush. Remove any squeezed-out glue.
15. Rout a stopped groove in the back of each post, centered and sized to fit the side panel’s picket tongues (Photo 4). Square the bottom end of each groove 4 in. from the post’s bottom edge.
Glue Up the End Assemblies
Each side panel mounts between two posts with tongue-and-groove joints (Photo 5). These end assemblies are large, so enlist a friend to help. Work on a flat surface, so you don’t glue a twist into the assembly.
16. Lay the posts on top of three pipe clamps, spaced far enough apart for the side panel to fit between them. Position the clamps so they’ll be right under the side panel rails.
17. Position the side panel between the posts. Set it on blocks, so the picket tongues align with the grooves.
18. Test-fit the joint. Add three clamps on top of the posts, directly over the panel rails, and slowly draw the joint together. Square the assembly by making sure the panel sits 4 in. from the bottom of each post. Apply even clamping pressure above and below each joint. The panel’s rail shoulders should fit tightly against the posts.
19. Disassemble the joints, apply glue to the tongues and grooves and draw the assembly back together. Remove any squeezed-out glue. If gluing both tongue-and-groove joints at once is too nerve-wracking, glue one joint at a time.
Make the Beams and Rafters
The beams and rafters (C and D) lock together with half-lap joints. The notches have to be located precisely, so the assembled beams and rafters will fit properly around the posts at the top of the arbor.
20. Cut the beams and rafters to width and length.
21. Clamp the two beams together and lay out the two outer notches (Detail 2, below). Make sure the ends of the beams are flush. Otherwise, the notches won’t line up correctly. Lay out the inner notches. They’re evenly spaced between the outer notches.
22. Cut the notches using a circular saw, with the blade set to cut to the bottom of the notch (Photo 6). Use a chisel to clear the waste and smooth the bottom of the notches (Photo 7).
23. Gang the five rafters together and cut the notches in them the same way. The rafters have only two notches; they’re 40-1/4 in. apart.
24. Make a pattern (Detail 2) and mark the ogee profiles on the beams and rafters. On the beams, the notches are at the top; on the rafters, the notches go at the bottom. Saw out the profiles (Photo 8).
Build the Gates
The gates (E) are layered, just like the side panels, but they go together differently and feature robust mortise-and-tenon joints.
25. Cut the hinge and latch stile components (E1 through E4) to length and width. Cut the loose tenons (E5) to size, too. The last 1-1/2 in. of their top edges slope 1 in. to shed moisture.
26. Glue the hinge and latch stiles by sandwiching an inside stile and a loose tenon between the outside stiles. Keep all the pieces aligned and the edges flush when you clamp. It helps to tack the pieces in place as you stack them together. After clamping, remove the squeezed-out glue—don’t forget the bottom of the mortises. After gluing, you’ll have three-layer stiles with flush edges, open mortises at the top and tenons protruding from the bottom.
27. Cut the bottom gate rails (E8) to width and length.
28. Make an arched pattern for the outside top gate rails (E6, Fig. C, below).
29. Cut blanks for the outside top gate rails. Cut the ends of these blanks at 70-degree angles, spaced 18-3/4 in. These angled top rail blanks must be the same length as the bottom rails.
30. Use reference points A and B on Fig. C to position your pattern on the blank. Transfer the arches and cut out the rail.
31. Make an arched pattern and cut the blank for the inside top gate rail (E7, Fig. C, below). This rail extends beyond the outside top rails to create the tenons. Cut the ends of this blank at 70 degrees, spaced 25-3/4 in. This rail is as long as the gate is wide.
32. Use reference points A and B on Fig. C to position your pattern and transfer the arches. Establish the two tenons by extending lines at 90-degree angles from the edges. Cut out the inside top rail.
33. Glue the inside top rail to one of the outside rails.
34. Glue the gate frames together (Photo 9). Clamp one bottom rail between the stiles, under the protruding tenons. Apply glue inside the mortises at the top of the stiles and to the tenons on the two-layer top rail. Install the top rail. Make sure the gate is square. Clamp the mortise-and-tenon joints at the top and glue and screw the tenons to the bottom rail.
35. Install the pickets (E9), using spacers, and fasten them with glue and screws. Then glue and clamp the remaining top and bottom rails.
36. Seal the exposed end grain on the tops of the gates with epoxy or thinned waterproof glue.
Install the Arbor
37. Install the anchor posts (Photo 10). Treated timbers are never straight. So that they’ll seat flush inside the hollow posts, joint adjacent faces of each 4x4 to create a flat, square corner. Rout a clearance chamfer to avoid hardened glue inside the post. Slide the 4x4 halfway into the hollow post, leaving 36 in. exposed, and fasten it to the inside corner with 2-1/2-in. deck screws on both sides (Detail 3, below). For longest life, orient the 4x4s so the “factory” ends go in the ground and the ends you’ve sawn go inside the posts.
38. Determine the arbor’s position in your garden and dig 8-in.-dia. x 40-in.-deep holes for the posts. First, drive a stake to mark the center of each hole. Establish the holes by spading down about 6 in. on all four sides of the stake. Then go to town with a post-hole digger. Using a level, determine the ground’s slope and mark the hole that sits at the highest grade.
39. Install the first end assembly (Photo 11). Plumb the post that goes in the hole at the highest grade (Photo 12). Starting with this post assures that all four posts will be above grade. When the first post is staked in position, level the assembly front to back (Photo 13). Then plumb the second post.
40. Use this staked assembly to install the other end assembly level, plumb and square (Photos 14 and 15).
41. Install the beams and rafters (Photos 16 and 17). Fasten them to the posts with screws and plugs.
42. Screw on the post caps after sealing the joints with silicone caulk (B5, Photo 18).
43. Fill and tamp the post holes (Photo 19).
44. Make and install the post trim (Photo 20).
45. Install the gates (Photo 21). Make sure the gap between the gates is large enough, at least 1/4-in., so they swing freely. Install a latch to close the gates. I used a large hook and eye screw combination mounted on the back of the gates for appearance. To hold the gates open, I installed a second hook to one side panel and a second eye screw to the other.
46. If you want to maintain the look of the fresh cedar, apply a finish. I used Penofin’s Western Red Cedar exterior stain. You should plan to recoat any exterior finish biennially. Without finish, the cedar will weather to gray within one or two seasons.