Building on crushed a’a

[Schoolmaster]

Not to bore with too many details, but I got a small lot of crushed and graded a’a and I’d like to put a building on, something like 12x24 or 16x or something, haven’t decided yet. My place here in Pune was easy-peasy, as we dug down a few inches to pahoehoe, dumped in fill, leveled and dropped some tofu blocks.
Just not sure what to do on a’a though. Do I have to get a truckload or three of cinder and shore it all up first? Does that cinder have to be rolled and compressed? My mind goes 100 places at once trying to figure out what needs to be doing to make it buildable.

[Chas]

I know when we built, the grading guy said that the building inspector would reject the foundation if they saw any red cinders. I think he said the red cinders never compact and cause it to be unstable.

[1voyager1]

I am not a civil engineer.
But, Grading the lot, with its mix of particle sizes and depth, should give a much better (more stable) surface to erect a building on.
Black  cinders do crush and screen into a much better material than red does, but probably not good enough.
Hauling truck loads won't give the depth and variety really needed.

If you're bound to build on a-a, pillars on leveled blocks might a better way to go.

[kalakoa]

IME cinders eventually crush to sand. If it's "load-bearing" I always use base.

Worse: bits of cinder will get tracked into the house -- where they're sharp enough to scratch up any kind of hard flooring.

[Schoolmaster]

Guess I should have chosen my words more careful.
I didn’t mean cinder, but rather the grey 3/4” like I used for the full and driveway I have here.

Now, would I need a truckload to fill the whole building area or would I just level out the places for the pier blocks?
I think I’m more curious than anything. Not sure if I’d build on here the more I think about it. But I’ve always wondered.

[Durian Fiend]

Crushed and grade A'a sounds like a satisfactory foundation surface to me. I'd just level out the spots for pier blocks.