Flagstone patio over recent excavation/fill?

[kellyjones1]

Recently - back in May - we removed a buried fuel storage tank. We dug out about 6' deep, maybe 8 feet wide, and 12 feet long. The hole was refilled by the excavator, and though the excavator did a bit of 'tamping' with the bucket, not a lot of soil compaction was done. Since then, the soil has sunk maybe 8 inches. This is in Western Oregon; the soil is mostly clay.

We'd like to put a flagstone or paver patio over this area. What type of soil prep is necessary? Do we need to re-excavate the entire pit, and refill/recompact layer by layer with a jumping jack? Or can we get away with a shallower re-excavation? Or is there some way to do it with no excavation at all?

Is there some more expedient way to accomplish this? Just looking for the lowest cost/effort way to prep this area for the patio, without having to worry about re-doing it in a few years.

Thanks,

Kelly

[jmeehan]

You can get away with a shallow excavation IF you dry lay the flagstone. Expect it to settle. If you dry lay it, then you just life the flagstone and add sand as needed. No problems with cracks or other problems because you can easily fix them.

[cshenk]

wrote

We are considering same here. Have a fairly level surface now and just need a bit of sand to go down then stones.

[Kelly]

Thanks for the reply. Can you define 'shallow'? How deep do you think I should go? Or, does it not matter, because unless I go full depth it will always settle?

The area I'm talking about paving is right next to another area (which I also will pave) which is on undisturbed soil, and has a concrete slab over it. Thus part of the flagstone will be on concrete, part will be on the excavated soil. It's relative settling between the two areas that I'm concerned about. Dry laying is no problem, that's what I was figuring on anyway.

Thanks,

Kelly