Two 6×6 PT posts extending to 7’6″ above ground, placed with 12’8″ between them.
2 2x8x6′ sideways beams, one at the top of each post
4 2x8x16′ longway beams (the span between supports is 12’8″)
16 2x2x6′ rafters
2×4 angle braces at all the corners
I did end up going with much deeper holes, burying 4 feet of 12-foot posts. I used .60 pcf treated lumber for the posts. They came pre-stained brown, so they don’t look that awful green color. All the rest of the wood is all-heart redwood.
I ended up not cutting notches in anything, instead going with the much simpler method of just double-diagonal-screwing the joints between the various 2x8s (a method I saw in a number of Youtube videos). The 2x2s on top are screwed in place with a single screw straight down at each joint. Each diagonal brace is held with a single lap screw to the post and two carriage bolts at the top. The beams that are flush with the post are held there with two 1/2″ carriage bolts and a couple screws.
Pergola Bench Seat Plans
You can also do this and add a swing set bench instead of swings: