I designed and built this play structure for my kids. It's ~9' high to the top of the rails, and the deck is 6'6" x 4'.

Giving credit where it's due -> I relied heavily on the 10 part series How to Install and Flash a Deck Ledger, Start to Finish from the Fine Homebuilding YouTube channel throughout this project.

Step 1: Layout

I planned and tested the positioning of the structure for a couple of weeks. The yard has an aggressive slope into the back corner, so I decided cementing in posts would be the best way to go. Once we were about happy with where the structure would be built, it was time to break ground.

Step 2: Post Holes

Since I'm in Michigan I needed to dig down below the frost line (42") to avoid frost heaving. We rented a 12" post hole digger for the task. The soil had a lot of clay in it, so this turned out to be a large undertaking.

After we were happy with the holes, I poured 15lbs of Quick-crete around 8' 4x4s. I did my best using 2 levels, an extra set of hands, and the string frame to make sure they were plumb and square to each other.

Step 3: Deck Framing

I framed the deck with 2x6 construction lumber. Once it was square and level, I trimmed off any excess on posts and boards.

Step 4: Rail Posts

I added rail posts in a configuration to allow for a post in each corner, one on the opposite side of the two openings, and one in the middle of the long closed off stretch. Each of the posts was attached using decking screws and a configuration of blocking and structural screws common in deck building.

NOTE: The pictures don't capture all of the hardware used. Info on the techniques used can be found in this video.

Step 5: Decking and Slide

I used some pine deck boards with penny nails as spacers. I had to cut out notches for posts, but the structure is relatively square and level so it was pretty easy.

I found a used plastic slide from somebody locally. I'd encourage you to browse local marketplaces. There are a lot of old play sets around and the slides last forever. Since the structure is a bit higher than recommended for the slide, I ended up cutting a wedge to screw onto the deck where the slide attached.

Step 6: Finishing Railings

For the deck sides, I attached 1x10s to hide all the structural screws.

For the rail sides, I alternated 1x2 and 1x6 boards in a pattern I liked, and used spacer blocks to make sure the spacing between boards was even. I predrilled all of the holes to avoid splitting, and attached them to the rail posts.

For the rail tops I just used more of the pine decking, and used a circular saw to lop off the corners.

After everything was attached I went around with a belt sander and palm sander to round rough edges and scrub off any rough spots. I also filled all the screw holes and sanded them over as well just to make it look a bit nicer.

Step 7: Ladder

I watched a couple of YouTube videos for building ladders and came up with this design. Just a bunch of butt joints with supports. I didn't attach it to the structure because it leans in and is heavy enough not to cause concern. It also makes it easy to move for mowing.

Similar to the railings, I went all over the thing with a belt sander to take off all the rough edges and corners.