How to Build a Detached Concrete Patio Cover

Choose the location for all four corner posts. The posts should be equidistant, positioned to form the corners of a rectangle or square. To check that the locations you have chosen form perfect 90-degree angles, snap a chalk line around the entire perimeter of the square or rectangle. Choose one corner. Measure 3 feet down one chalk line from the corner and mark that position as point A. Next, measure 4 feet down the opposing chalk line from that corner. Mark that position as point B. Finally, measure the distance between point A and point B. If the distance between point A and point B is not 5 feet, then that corner of the pergola is not a right angle and you must adjust the post locations accordingly. Repeat this process for each corner until all the corners form 90-degree angles. Secure steel post-base anchors to the concrete patio at the four corners with 1/4-inch concrete screws. Drill pilot holes for the concrete screws into the concrete with a hammer drill.

Ask a partner to hold the posts level and hammer them into the anchors with 6d nails.

Cut four 2-by-6 support beams that are 12 inches longer than the distance between the posts on the south side of the patio. Clamp one of the beams to the posts on the south side, with equal lengths of lumber protruding from each side of the posts. This beam should be secured to the posts 3 inches from the top. Check the beam with a level then secure each end of the beam to the posts with four 3-inch No. 10 screws. Clamp a second beam to the same posts, on the opposite side of the posts from the first beam. Secure the beam to the posts in the same way that you secured the first beam. Repeat this process for the posts on the northern side of the patio.

Measure the distance between the two pairs of support beams, then add 18 inches to that length. Cut 10 2-by-6 crossbeams to this length. The crossbeams will lie perpendicular across the support beams, with a pair of crossbeams on each side of the corner posts and three pairs of crossbeams spaced evenly through the middle of the pergola. Depending on the size of your pergola, you may want additional pairs of crossbeams. The optimum distance between pairs of crossbeams is approximately 2 1/2 feet. Lay the crossbeams centered across the top of the pergola and mark the crossbeams where they intersect with the support beams. Use a table saw with a dado blade to make 2 1/2-inch notches in the crossbeams where they will intersect with the support beams from Step 2.

Install the crossbeam pairs across the pergola with 5-inch wood screws drilled through the top of the crossbeams and into the support beams.

Cut eight 2-by-6 diagonal braces with 45-degree angled ends to attach to the posts and support beams. Use 2 1/2-inch screws to secure the braces to the post and support beams.

Cut five 2-by-6 pieces of lumber to fit perpendicular over the cross braces, with 6 inches hanging out over each end. These are the slats that will sit on top of your pergola. You may cut more than five if you feel the size of the pergola warrants it.

Clamp the slats of the pergola to the top of the cross braces. The slats should be evenly spaced and perpendicular to the cross braces, centered over the top of the pergola so that the slats hang over the side of the pergola by 6 inches. Mark the places where the cross beams and the slats will intersect.

Remove the slats and use a dado blade to cut a 2 1/2-inch notch for each place where the slots and crossbeams will intersect.

Install the slats across the pergola with 5-inch wood screws drilled through the top of the slats and into the crossbeams.