However far you go down, it is recommended to put a layer of geotextile on the dirt, then the gravel, then whatever topping you desire. This will even stand up to the destructive hooves of cows and horses, even when the ground gets wet. A friend of mine had a winter "muddy" area by his barn where the cows would sink almost 2' into and even his wife with waders got stuck and had to be rescued. In the summer he dug down, spread the geotextile then the gravel. It's been almost like concrete since.
I buy geotextile in rolls 15' wide and I forget how long but even Amazon sells smaller sizes. Or ask a local farmer or contractor if you need only a small piece.
Our county government ag office sells partial rolls (office has some initials like FSA or some such). Probably many of these offices do.
But, it is not necessary to put under pavers in typical environments. It is helpful to resist hooves punching through compacted crush rock- feeding pads, creek access. You will never get a punching load on a sidewalk sufficient to drive a brick into the compacted base unless it is mush beneath. Out pavers are on a sandy river bottom soil. A few inches of compacted ungraded crushed rock, couple inches compacted sand, done. Has been stable for 2 decades.
Ideal preparation likely depends at least in part on local soil conditions, local drainage, expected load, and winter frost depth. Check with the local building code and/or building department.
Here in Cincinnati I've seen paver installations in the right-of-way that have stayed flat for years, and others that were buckled within 3 years. Personally I would rather exceed the minimum recommendations for the base the first time rather than take up uneven pavers, dig out inadequate base, and start over.
rototiller it. If I have to dig any size pad or trench I grab my little tiller and break up the soil to make it easier. Are you using brick pavers or those large flat stones people call pavers? That may make a difference in the prep.
I have to second the geotextile. Several years ago I put it down under part of a patio. Note I said part. I ran out and didn’t use it on another section. Other than the fabric the whole patio was done the same way.
Fast forward 15 years. There is some settling in the area without textile and the area with it is dead flat.
It’s not so bad that I’d take up the uneven area to fix it but I’ve use geotextile on every project since then. It’s not expensive.
The overwhelming advice from farmers and builders is to use geotextile in such situations. It works in a variety of soil and subsoil conditions. Some provide anecdotal "evidence" questioning the need in specific cases and some cases indeed don't benefit, but it's good insurance for universal use in a huge variety of conditions. I consider it as important as a foundation for a building, as important to paying attention to the frost line. Just my opinion (and the experiences related by other farmers and builder friends.) It's cheap insurance.
The use of geotextile is required by certain government agencies that provide funding to individual for ag-related improvements.
I agree. The 12" recommendations are for driveways for heavy vehicles. Walkways carry a few hundred pounds at best and only need 2" of fill (over a heavily compacted base) for leveling purposes. My walkways in Michigan have faced deep frosts for 20+ years without heaving.
Many years ago I was a Class A Contractor and built a house near Chester, VA. Cutting to the chase, spring came and we were putting in the driveway and final grading. The Front end loader arrived, unloaded in the street, and pulled onto the lot. The operator left it running while he readied the truck to park.
We looked and this stuff that looked like chocolate pudding had sprung up around the tracks. He tried to drive forward, then back, and the loader kept sinking. The operator jumped off and we watched as it sank almost out of sight. Nothing was showing except the roll bar and the exhaust stack. We left it there for about a month and brought out a giant wrecker and pulled it up and out. It started and they loaded it and carried it away.
I found a local old geezer who knew his stuff and put me onto geotextile fabric. I rolled it out and back dumped 6 or 8" of gravel on top of it. That was at least thirty five years ago. I rode by there recently and the driveway is still there and fine.
Believe me, this is the short version of that story.
