How Do I Build a Pergola on a Dirt Surface?

Mark a rectangle in the dirt outlining the pergola area. The corners must be 90-degree angles. To ensure 90-degree angles, measure the diagonals of the rectangle. If they are equal, the corners are 90 degrees.

Dig a hole for each corner post 24 inches deep and 9 inches in diameter, centered on the corner points. The hole must be deeper than the frost line. If local ordinances dictate a different size for postholes, follow the local regulations.

Set a wooden post made of weather-proof lumber in the middle of each hole. The post should be 4-b- 4 inches or larger, and should be a little over 2 feet longer than you want your pergola’s height to be. Check the posts for level with a carpenter’s spirit level. Brace the posts in position with scrap lumber. Pour 1 inch of gravel around the post for drainage.

Mix quick-drying cement according to the package directions. Pour the wet cement in each hole around the base of the post. The cement should come up to about 1 inch below ground level. Allow 24 hours for the cement to cure.

Measure each post from ground level to the desired pergola height. Saw the posts level on top to this height.

Cut four support beams from 2-by-10 lumber. They should be of equal length and at least 1 foot longer than a long side of the rectangle measured from one post corner to the next. If you want a longer overhang, cut them longer.

Place one support beam on the outside of the side of the rectangle at the top of the posts with the same amount of overhang at each end. The top edge of the support beam must be level and flush with the top of the posts. Place a second support beam on the inside of the posts and line it up with the first beam. Clamp the support beams to the posts. Drill two evenly spaced pilot holes all the way through both support beams and the post between them at each end of the beams. Place a lag bolt through each pilot hole and tighten. Repeat this procedure to secure support beams to the opposite side of the rectangle.

Stand a 2-by-6 inch wooden rafter on edge on top of the support beams and perpendicular to them on one end of the pergola. Line it up even with the outside edges of the posts. Place a series of additional rafters across the pergola so there is about 1 foot of space between each one and the last one lines up with the outside edge of the posts on the opposite side. Screw the rafters to the support beams with 8-inch galvanized deck screws from the top.