Prepare to Build the Pergola
Obtain the necessary permits from your city or county's building or planning departments. A pergola is a large enough structure that a permit is usually required. At the same time, be sure to "call before you dig" to make sure your footings won't go into an underground gas, water or electric line.
Clear the area you plan to use for the pergola of rocks and debris. If you need to level the area, use a shovel and a level to do that now. You can build a pergola on a slope, but it will require you to use different lengths of wood for the support beams.
Mark one corner of your pergola with a stake. This will be your starting corner. Using a tape measure and string, mark the other three corners. Make sure that your stakes mark out an exact square or rectangle in the size you've decided.
Dig holes at the points marked by each stake. The holes should be square and the size you've determined for the footings on your plan, and the bottoms must be level. You can buy premade footings, or you can mix concrete to make your own. Place the post supports into each hole.
Cut the wood for the frame of the pergola. These are four 4-by-4-inch corner posts, four 2-by-6-inch support beams and two 2-by-2-inch crossbeams. Use a template to draw curved notches at each end of the support beams and crossbeams, and then cut them out with a jigsaw. You can cut the rafters and caps as you build the pergola.
Paint or stain the wood before you build the pergola if you want it painted or stained. It's easier to do this now than when it's built, and you can cover the areas that will be connected. Cedar can weather naturally if you like, but other woods should be stained or sealed to keep them from rotting.
Build the Freestanding Pergola Frame
Mix the concrete with water to make a sloppy or wet mixture. Pour it into the holes, using care not to disturb the post supports. If you do jog a support, you can adjust it while the concrete is still wet.
Erect the corner posts after the concrete has cured. If you're working on a slope, put up the longest one first. Clamp it into the post support and use the level to make sure it's plumb both vertically and horizontally. Once it's plumb, bolt or nail it in place in the post support.
Repeat Step 2 with the other three corner posts. Make sure that the tops of each post are at exactly the same height.
Clamp a support beam near the top of two of the corner posts. This side and the side parallel to it will each have support beams on both sides of the corner posts, and the ends of the remaining two support beams will rest on top of them. The distance between the top of the straight edge and the top of the post should be the same as the height of the narrow end of the curved notch you cut in Step 5 of Section 1.
Ensure that the support beam is level, then attach each end to the post with four 3-inch wood screws. Clamp the other support beam for this side on the opposite side of these two posts, make sure it's level, and secure it with four 3-inch wood screws. Attach the two support beams on the parallel side the same way.
Use the jigsaw or dado blade of a table saw to cut notches into the crossbeams where they'll cross the support beams. Fit the notches of the crossbeams over the ends of the support beams, make sure the beams are level, then screw each into the two support beams.
Finish the Freestanding Pergola
Brace each upper corner with two diagonal pieces of 2-by-6-inch boards. Cut them to the length you choose, and cut each end to a 45-degree angle. Attach them to the support posts and the top beams with wood screws.
Decide how many rafters or slats you want across the top of your pergola. Your decision should be based on the size of the pergola and how close together you want them. For an 8-by-8-foot pergola, for example, you may choose to have five rafters.
Take a 2-by-4-inch board for each rafter and cut them all to the same length as the crossbeams. Use a clamp to hold each rafter in place so you can mark where they need notches to go over the crossbeams. Use the table saw with the dado blade to cut the notches.
Put the rafters on top of the crossbeams. Make sure they're all the same distance apart. Drill pilot holes over the notches where they cross the beams, then attach them with 3-inch wood screws.
Make a cap for each of the support posts. You can choose to cut a pyramid design from a wood block, a simple flat cap that sits on top of the post, or let your imagination create a design that means something to you. Secure the caps to the posts with construction-strength wood glue and galvanized finishing nails.
Things You Will Need
- Building plan
- 4 wood stakes
- Tape measure
- 4 galvanized iron post supports
- 4 4-by-4-inch-by-12-foot lengths of wood
- 4 2-by-6-inch boards
- 2 2-by-2-inch boards
- Template for curved ends
- Paint, stain or wood-sealer (optional)
- Concrete mix
- Steel post-base anchors (optional)
- Galvanized nails
- 3-inch wood screws
- Table saw with dado blade
- 8 2-by-6-inch boards
- 5 (or more) 2-by-4-inch boards
- 4 wood blocks
- Wood glue
- Galvanized finishing nails
- When you're marking the corners and edges of the pergola, measure the distance between corner A, the first, and corner B, the second. This distance should be exactly the same as the distance between C and D, the corners of the parallel side to A-B. The line between A and C should be exactly the same length as the one between B and D, the lines perpendicular to the first two lines. The string at each corner should mark a perfect 90-degree angle.
- Cedar is one of your best choices for wood because it's better at resisting decay than most other woods. If you've chosen to use another material, then substitute that for the wood mentioned in each step.
- If you've decided not to level your pergola's base but to leave it on a slant, remember that the corner posts won't all be the same length. Make sure you cut each of them to the right length so that their tops will be level with each other. You can choose to wait until you've secured them in place to do this if you want.
- If you're building your pergola on an existing concrete patio, use steel post-base anchors instead of the galvanized supports mentioned above. Fasten the anchors to the patio securely.
- Build braces to keep the corner posts plumb if fastening them to the supports doesn't do the job.
- This is a simple and basic plan. You can easily modify it to change the size or shape, or to add your own design elements, such as a trellis along one side for more shade or to support climbing plants. You can see a variety of different pergola designs at the Whispering Crane Institute's blogspot.