We’ve equipped our trellis with a bench, making it a great place to relax and enjoy a warm summer afternoon. If you decide to do without the bench, the trellis becomes an elegant arched gateway to your garden. For good glue joints, it’s important that you start with lumber that’s not too wet. To avoid problems, buy your wood at least a few weeks before starting the project. Stack the lumber in your garage or basement, with spacers between layers, and aim a fan at the pile. Be sure to use water- resistant exterior glue, such as Titebond II, for assembly.
This project was originally published in the April 2002 issue of Popular Mechanics. You can find more great projects at Popular Mechanics DIY Central.
Step 1: Materials
Step 2: Posts and Top Frame
Make each of the two top beams by gluing up three layers of 11⁄2 x 5-in. stock. To avoid cutting traditional mortises for the post tenons, make each center layer from three separate pieces as shown in the drawing on page 124. Cut a notch in each inner end-beam segment to form the mortises in the assembled beams. Apply glue to the mating faces for one beam, then place the center layer on one of the outer boards. Use screws to keep the pieces from shifting (Photo 3). Place the third layer into position and clamp (Photo 4).
Then assemble the second beam in the same way. Make a template for the end shape of the top beams and trace the shape onto the beams. Use a band saw to cut the beam ends. Follow the same procedure for the stretcher ends. Lay out the notches along the bottom edges of the stretchers and use a dado blade to make the cuts. Bore screw pilot holes and plug counterbores in one operation with a combination bit. Then, fasten the stretchers to the beams with screws (Photo 5). Use a plug cutter in the drill press to make plugs and install them over the screws. When the glue dries on the plugs, cut them off and pare them flush with a sharp chisel.
Step 3: Lattice Construction
Lay out all parts for one of the lattices and spread glue on the joints. Assemble the frame and apply spring clamps to each half- lap joint (Photo 7). When you’re done, compare opposite diagonal measurements on this grid to make sure the assembly is square. With both frames built, cut the caps to size and chamfer the top edges. Spread glue on the top end of each lattice and on its cap, then clamp the parts together (Photo 8). Place a post on the worktable and position one of the frames on it. Mark and bore screw pilot holes into the post. Fasten the lattice to the post with brass screws. Screw the opposite post to the frame and repeat the procedure for the other side of the trellis.
Step 4: Building the Arches
With both arches assembled, create a template for the arch shape. First make a beam compass from a roughly 32-in.-long board and a dowel. Bore a hole for the dowel at one end of the board and a matching hole in the template panel that defines the center of the arch. Next, measure the inner and outer arch radii from the dowel hole on the board and bore holes for a pencil at those marks. Use the beam compass to scribe the arch on the template stock (Photo 10) and then cut to the lines to finish the template.
Clamp the template to one of the arch blanks and trace the outline (Photo 11). Lay out the straight cuts where the arches join the posts. Cut out each arch with a sabre saw (Photo 12), and sand the sawn surfaces. Cut the arch supports to size. Lay out the screwholes for both the arches and the supports, then bore and countersink the holes.
Step 5: Assembly and Finishing
lattice assemblies into place and check their fit. Next, position the arches and bore pilot holes into the posts. Fasten the arches with screws (Photo 13) and then attach the vertical supports. Cut the bench parts to size. Use your table saw and dado blade to cut the notches in the ends of the aprons and rails, and readjust the blade to cut the notches on the bench-support cleats. Lay out the stopped dadoes in the cleats and aprons and use a Forstner bit to bore out most of the waste. Finish the joints with a sharp chisel.
Turn the trellis upright, screw the bench cleats to the lattice assemblies (Photo 14) and test fit the bench frame. Cut the seat slats to size and rout the chamfer on the top edges of the slats. With the dry run complete, disassemble the trellis and take the parts to the site. Reassemble the trellis using glue at the top mortise-and-tenon joints. Make sure that the posts are square to the beams while the glue sets. Reattach the bench cleats with screws. Then, glue the bench frame to the cleats. Lay out the bench slats and bore the holes for screws and plugs. Screw the slats to the frame and plug the holes. Cut the keystone blocks then glue and clamp them to the arches. Finally, apply one coat of Cabot Clear Decking Stain.