I’m reading you should put silica sand at the bottom of a metal fire pit as long as it doesn’t have any holes. It has no holes at the bottom. I looked up some brands but they have bad reviews saying the sand got scorched and wasn’t fire proof, and other kinds of sand with limited reviews to know I’m doing the right thing. I’m just not totally sure it’s what I should use. What about lava/volcano rocks? I keep coming across this type of rock. Just not sure what to use.
Also, the fire pit stands on 4 short legs. Should I put anything underneath it? I’m not concerned about it ruining grass underneath I just want to be sure it’s safe.
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The gravel is a good idea because reasons. Reason one being that gravel provides much better drainage than sand which will help keep the rather nasty water (rainwater through ashes is the traditional way to make lye) out of the yard or from freezing and heaving in the winter.
The second reason being that gravel compacts better than sand, and can be compacted by beating on it where as sand must be vibrated. A compacted base obviously means less settling down the road.
So while it's not essential it does add a bit of durability for the low price of a couple bags of paver base and thumping on it with a tamper. It's pretty cheap insurance against resetting pavers. But really the biggest recommendation is that you need not be concerned with the drainage and compaction properties of your existing soil.
You fill it with the regular sand so that the pavers remained properly spaced as they settle. Without that sand acting as a buffer you're liable to get pavers that move too much laterally and don't have enough of a gap between them for the polysand to get in.
I'm not sure about the gravel, but I suspect the answer is something along the lines of: Not strictly speaking, no, but it's probably a good idea because reasons.