Can these old community-built play structures actually be safe given the framing issues?

Those 90s-era castle playgrounds rely on massive **redundancy** rather than modern residential code. When you’ve got a dozen towers all cross-braced together, the load isn't concentrated on a single failure point like it is on a backyard deck. Even if a few of those buried 4x4s are rotting at the ground line, the structure often stays standing beacuse it's essentially one giant, rigid crate. The 4x4 posts buried in the dirt are likely CCA-treated timber, which was the standard back then. That stuff was loaded with arsenic and chromium; it’s nasty, but it resists rot significantly better than the modern lumber you buy today. While burying wood is a cardinal sin now because of moisture traps, those old-growth, heavy-duty treated posts can easily last forty years in the right soil conditions. They’re basically petrified. As for the lack of joist hangers, many of those volunteer builds used ledger strips or just massive amounts of 20d nails and trough-bolts. If they spaced the joists close enough—sometimes as tight as 10 inches—the load is distributed so widely that a single connection point failing won't cause a collapse. You’re seeing sagging because 2x4s and 2x6s aren't meant to span long distances, but a saggy walkway is usally a serviceability issue, not an immediate safety catastrophe. The handrails and monkey bars are where the 90s logic is most obvious. Code today requires graspable rails for a reason, but back then, a 2x4 was considered fine for a kid. If you’re worried, check the **bolt tension** on the monkey bars. If the wood hasn't turned to mulch around the bolt hole, it's likely still solid. These structures usually give plenty of warning—creaking, swaying, or visible splintering—long before they actually give way. It’s definitely not up to modern standards, but it's likely more stable than it looks.

That bit about the wood being petrified is wild. I always thougt wood in dirt was a death sentence within a few years. How do you even tell if it's the old CCA stuff versus the newer treatment? I'm planning a tiny platform in my yard and I'm terrified of getting the wrong lumber and having it rot out before my kids even grow up. If I see a bit of swaying in a structure that big, is that a sign to run, or is a little movement normal for those old volunteer builds?

Spotting CCA is tricky once it's weathered to gray, but the old stuff rarely has those 'incising' marks—the little slits—you see on modern pressure-treated lumber. Also, funny enugh, modern chemicals like ACQ are way more corrosive. They'll eat trough standard galvanized nails, whereas the old CCA was acutally pretty gentle on the hardware.

If you're seeing sway, check the base. A little flex in a high tower is just physics, but if the posts are moving *inside* the ground, you've got a problem. Try the screwdriver test: poke the wood right at the ground line. If it sinks in like butter, the core is toast even if the outside looks petrified.

Soil type matters a ton for those buried posts. If it's sandy and drains well, they might last forever, but heavy clay will rot even the old CCA wood eventually. You also need to look for 'bleeding' hardware. If there are dark, black streaks coming from the bolt heads, the carriage bolts are likely rusting out from the inside. That’s a bigger hidden danger than a sagging walkway. Also, check the deck boards for cupping. If they're holding water, the sub-structure is getting soaked every time it rains, wich accelerates the rot regardless of how thick the beams are.

Keep an eye on the 'checking' in those 4x4s too. Those deep cracks are normal for air-dried timber, but if a check lines up perfectly with where a bolt is thru-mounted, it basically splits the structural capacity of that post in half.

Also, check the tops of those towers. If they didn't cap the end grain of the vertical posts, water just soaks down into the core like a straw. You can have a post that looks solid on the outside but is basically a tube of compost in the middle. Give the wood a good poke with a screwdriver high up to see if it sinks in.