Popular Mechanics' backyard cedar pergola and Sunset's basic square pergola are some plans to build pergolas. The Popular Mechanics plan calls for pressure-treated 4x4 cedar posts built on a concrete base, while Sunset's plan uses larger posts built on a bed of gravel.
To build Popular Mechanics' backyard cedar pergola, lay out the post positions using steel post-base anchors on a concrete slab. Mark the screw locations, and then use 1/4-inch Tapcon screws and a hammer drill to secure the anchors to the concrete. Drive nails through each anchor hole into the posts, bracing the posts if necessary. Cut four 2x6 cedar support beams to length, and then cut curved notches in the ends with a jigsaw. Clamp and level the beams, secure them with four 3-inch screws, and then duplicate your work for the second, parallel pair of beams.
Cut notches in the 2x6 crossbeams with a dado blade in a table saw so they fit over the support beams. Make the curved end cuts with a jigsaw, and then install the three crossbeam pairs by screwing them to the support beams. Add cedar trimpieces to the posts using construction adhesive and galvanized finishing nails before fastening 2x6 diagonal braces to the posts and beams with screws. Attach five 2x4 slats with curved ends to the crossbeams with 3-inch screws after cutting notches to accommodate the crossbeams with a dado blade. To complete the project, cap the posts with pieces of square, beveled cedar.
The Sunset plan is similar, but requires concrete, rebar and form lumber to create footings to secure the posts in the ground. Unlike the Popular Mechanics plan, the floor of the Sunset pergola is covered with gravel instead of concrete.