In this video, This Old House general contractor Tom Silva shows a simple way to construct a strong and sturdy picnic table.
1. Lay out the top of the picnic table by setting five 8-foot-long 2x8 boards edge-to-edge. Be sure the best-looking surface of each board is facing down.
2. Place 16-penny nails between the boards to act as spacers.
3. Cut three 2x4 cleats to 32 inches long. Miter-cut both ends of each cleat to 45 degrees.
4. Apply polyurethane construction adhesive to the 2x8s across the center of the 8-foot-long tabletop.
5. Set a 2x4 cleat into the adhesive and fasten it down with 2½-inch-long decking screws.
6. Glue and screw down the remaining 2x4 cleats, positioning each 16 inches from the end of the tabletop.
7. Cut the table legs from pressure-treated 2x8s. Trim the leg ends to 28 degrees.
8. Cut and fasten a 2x8 cross brace to each pair of legs, forming two A-frame assemblies.
9. Apply construction adhesive to the top, inside surface of the legs, then attach the A-frame leg assemblies to the 2x4 cleats with 4-inch-long decking screws.
10. Cut and install two 2x4 diagonal braces to the underside of the tabletop. Screw the diagonal braces to the tabletop and to the cross brace on the leg assemblies.
11. Fortify the connection between the cross brace and legs with ⅜-inch-diameter x 3½-inch-long galvanized carriage bolts. Install two bolts to each leg.
12. Use an adjustable wrench to tighten hex nuts onto the carriage bolts, then peen over the bolt ends with a hammer to prevent the nuts from loosening. Flip over the picnic table and set it on its feet.
13. Cut two 2x6 seat boards and three 2x4 cleats for each picnic table bench seat. Glue and screw the cleats to the underside of the 2x6s.
14. Apply adhesive to the top edges of the cross braces that extend out from the picnic table legs. Set the bench seats on top of the braces.
15. Fasten the seats to the braces with 2½-inch-long decking screws.