One of life’s great joys is being able to build a backyard fort for your kids, seeing them play on it and knowing they will brag to their friends about it. So naturally, I wanna build something big, aesthetic, functional and with tons of bells and whistles.
I’m wanting to use 4x4s for the main posts that are Quikreted into the ground. Reading up on digging post holes, I see that you’re supposed to plant them 1/3-1/2 way into the ground for however much is sticking above ground. But, I’m wondering if this rule of thumb is only for fence posts which are only fastened to one another along one direction and not for posts that would be fastened together in two directions.
Also, does this rule of thumb stick for every region of the world? Texas has some thick hard soil and I’d think this would mean they probably don’t need to be dug quite as deeply.
I guess the main question I’m really trying to zero in on is “What is the tallest platform height I should construct?”
My late husband built a huge fort using the plans and hardware from https://www.detailedplay.com/. Bought lumber locally. We had one child with many friends. Square footage of platform was important. We opted for the pirate ramp over the slide. Most kids just climb up the slides anyway. Plus slides get hot. Two climbing walls. Swing set. Monkey bars. Pull up bar. Ladder. Huge awning, because shade matters.
This thing was a tank. Rather than trim the pressure treated posts, David sunk the excess into the ground. Less than a foot.
Fast forward 14 years. It’s finally time to take the fort down. The pressure treated wood in ground contact was in amazing shape. The fasteners were at the end of their lifespan, not the wood.
Highly recommend. Edit: didn’t need to put posts 1/3 in the ground. That fort was self supporting. Not going anywhere.
I built a tower plus swings playground for my daughter 20+ years ago. IiRC it was a kit from Home Depot. This was pre-climbing wall craze so it had a slide and ladders.
It was not sunk in the ground at all.
When we moved I sold it on: the buyer disconnected the swing’s top bar from the tower and loaded the tower onto a flatbed.
When i was really little, my grandfather and father took like two weekends to build a three story tower and a two story playground for us kids. When we took it apart, something like twelve years later. the posts were sunk about two feet in the ground. According to him, they did that to prevent the whole thing from swaying too much. Something else to note, the floors were only about 5-6 feet each (kid-sized). So if you want multi-story, remember that you can shrink the stories. If you want any help with design or building this, just DM me
That’s what I would do if I were building one. Sink sono tubes with Simpson strong ties in the concrete. At that point, no worries about the post rotting in the ground.
It may not be necessary, but having a mechanical connection to supports would be the way for me to go.
Is the point of keeping the posts out of the ground to avoid rotting or to avoid issues with the ground shifting? The soil (in Sachse) is tough, black compact dirt.
I should confess that my brother and I already augered 3ft holes into the ground over this last weekend… so if we can use them I’d prefer to unless there’s a reason not to. Sono tubes with strong ties are sounding good (depending on price) unless the same result can be achieved by Quikreteing the posts in place followed by an outdoor sealant.
Here’s roughly the structure, many features of which I’m not married to, I’m going for minus support braces, awnings in the shape of ship sails, and the extra bells and whistles. The first level (unseen from this angle sits at 6.5ft while the highest level sits at 9ft. ~250ft^2 of platform space. Since it also has a tire swing and swings attached, I’m really wanting to know the structure is well stable.
Please let me know if you spot any improvements that can be made. (I’m going to opt for something different than ropes for support rails in the middle section)
What type of fasteners should I be using for connecting to the 4x4 posts?
I called up city ordinance people and told them what I was doing. Fortunately, they usually do not require permits for play structures and I’m going to design it in a way that it’s easy to disassemble in a few hours should any issues arise.
Thank you everybody for the comments and shared stories. I’m really enjoying reading about them and would love to hear more. If y’all have any pics of the awesome forts you described, I’d love to see them.
We had a Dallas Custom Swings (RIP) play scape thingy that had an elevated ‘clubhouse’ with a floor about 6 feet off the ground, with a beam that extended out from that with the end supported by a timber A-frame. None of it was buried. The A-frame ends were anchored to the ground with steel auger thingies.
If the structure shown above does not have the legs anchored into the ground, then there will need to be something that ties the legs together so they don;t shift apart or towards eachother and collapse.
Look like a cool project. When a kid, the neighbors build a fort, well actually a Castle. Was basically a 10’ x 10’, with up platform. What made it unique was it actually had a Drawbridge that raised and lowered. Used a crank wench like you have for getting a boat onto a trailer.
We all had “forts” but sure what we were defending against, surprised we didn’t all become survivalist.
Probably really stoopid silly, but I was actually wondering if there’s a way to extend the outdoor lifetime of cardboard by treating it with something, painting it or spray painting it.
Never underestimate the power of a cardboard box fort. You can buy your kids the fanciest things only for them to just have as much fun playing with the box.
I can remember when we got the box a new refrigerator came in (fall 1961, heavy thick walls. Begging my dad to keep it intact and not slice it off.
It was a spaceship (Mercury launches had just started) … actually more like as Space Shuttle considering how many of us were in it)
A fort (I’d probably not be alive but for the safety it provided)
Time Share and forerunner of Title IX (had to share with little sister and her friends … separate but equal was still in effect despite the Surpreme Court, it wasn’t segregation, it was health quarantine: cooties)
I always thought a company that made heavy duty boxes for sale at Christmas would make a fortune.
If you need to bury 4 x 4 posts, 18-24 inches deep is plenty. The support is caused by side friction between the concrete and the dirt. You can easily load 1000 lbs on a 2 ft concrete foot.