I went through something similar when we built ours. Gravel alone was a no-go for us too—turned into a swampy mess after just a few rains. Ended up using landscape fabric underneath, and honestly, it's been pretty solid since then. I think the key is definitely putting enough gravel on top to keep dirt from working its way down.
As for drainage, I didn't go quite as deep as 18 inches (props to your back, haha). Mine's probably closer to a foot deep, but I made sure it slopes away from the pit toward a lower area of the yard. So far, no standing water issues, even after some pretty heavy storms.
One thing I'd add though—make sure your fire pit walls are high enough and sturdy enough to contain sparks and embers. I've seen some DIY pits that look great but aren't really safe once you get a good fire going. Better safe than sorry...especially if you've got kids or pets running around.
Anyway, sounds like you're on the right track. Hope it turns out awesome!
I had a similar experience when we built ours a couple years back. Gravel alone definitely wasn't enough—after a few storms, it was like walking through oatmeal. I ended up going with landscape fabric too, but I also added a layer of compacted sand underneath the gravel to help stabilize everything. Has anyone else tried sand as an extra layer? It seemed to help keep things level and stable for us.
About drainage, I didn't dig quite as deep either—maybe around 10 inches—but I did put in a small French drain system leading away from the pit. It might've been overkill, but we've never had standing water issues since then, even after some pretty heavy rains. Did you consider adding any kind of drainage pipe or just relying on slope alone?
As far as safety goes, totally agree about wall height and sturdiness. One thing I'd add from personal experience is to pay attention to the materials you're using for the walls themselves. Some DIY pits I've seen use river rocks or certain types of stone that can actually crack or even explode under high heat (learned that one the hard way...). We ended up using fire-rated bricks on the inside lining and then decorative stone on the outside for looks.
Also, have you thought about seating placement? We initially put our chairs pretty close to the pit because it looked cozy, but quickly realized sparks and embers were landing way too close for comfort. Moving seating back just a foot or two made a huge difference in safety without sacrificing warmth.
Sounds like you've got most bases covered though—hope your pit turns out great and stays safe!
"I ended up going with landscape fabric too, but I also added a layer of compacted sand underneath the gravel to help stabilize everything."
Honestly, compacted sand can be hit or miss. I tried it once, and while it did stabilize things initially, after a couple wet seasons it started shifting unevenly. Ended up redoing it with crushed limestone instead—way more stable long-term. Also, French drains are great, but proper slope alone usually does the trick unless your yard is super flat...
Yeah, crushed limestone definitely holds up better over time. Did you use a plate compactor when you redid it? I found that made a huge difference in stability for my patio area. Also, curious if anyone's had issues with landscape fabric eventually clogging up and affecting drainage...I've heard mixed things about that.
I've always been a bit skeptical about landscape fabric myself... seems great at first, but after a few years it tends to clog up and cause more drainage headaches than it solves. Did you notice any pooling or soggy spots yet?