Before a gravel driveway goes down, the topsoil comes off, the subgrade is shaped and compacted, geotextile fabric goes on any soft or wet ground, and a compacted base course of ABC or crusher run is built in lifts. The surface is shaped with a crown, and ditches and culverts are set so water leaves the drive before the top stone goes on.
Start by taking things away
The first thing to put down is nothing at all. Topsoil, sod, roots and leaf litter have to come off the line of the drive. They are soft, they hold water, and they rot. Stone laid on top of them sinks unevenly and ruts.
Stripping goes down to firm mineral soil. In Western North Carolina that is often red or tan clay with some rock in it. In wooded ground, stumps and big roots along the route come out too. Anything that will rot later leaves a soft spot later.
The stripped topsoil is not wasted. It can be stockpiled and spread on the shoulders once the drive is built, so grass can take.
Shape and compact the subgrade
The subgrade is the native ground under all the stone. It carries the load. If it is soft or uneven, no amount of gravel on top will stay put.
It is graded to the line and slope of the finished drive. Low spots are filled with suitable soil in layers, and each layer is compacted. Then the whole route is compacted and checked for spots that pump or give under a loaded machine.
On a slope this is also where the drive is cut into the hill. The uphill side becomes a bank, and the downhill side has to be built up and compacted. That bank may need riprap or a retaining wall to stay where it is.
Geotextile fabric: when it earns its place
Geotextile fabric is a tough woven or non-woven sheet laid on the subgrade before the stone. It keeps the soil and the stone from mixing. Without it, clay works up into the base over time and the base sinks into the clay.
Fabric is not needed everywhere. On firm, dry ground it adds cost without much return. Where it pays is on soft clay, wet ground, seeps and fill. NCDEQ's design practice for stone construction entrances calls for fabric where there is seepage or a high water table, to improve the stability of the foundation. A driveway on wet ground faces the same problem.
On very soft ground, fabric often goes down first with a layer of coarse stone over it.
Build the base course in lifts
The base course is the main structural layer. In North Carolina it is usually ABC, aggregate base course, or a crusher run that compacts the same way. It is a mix of coarse stone and fines that locks into a hard layer when compacted.
It goes down in lifts, not one thick dump. Each lift is spread, wetted if it is dry, and compacted before the next goes on. A thick layer dumped at once compacts only at the top and settles later.
How thick the base needs to be depends on the soil and the traffic. A drive that will see concrete trucks and a soft cove bottom both need more. Our gravel types guide explains which stone goes in which layer.
Crown it so water leaves
A crown is a slight rise along the center of the drive so the surface slopes off to both sides. On a drive cut into a hill, the surface may slope to one side instead, toward the uphill ditch. Either way, rain runs off the edges instead of down the middle.
The shape is built into the base, not just the top stone. If the base is flat, the top layer will be flat too once traffic packs it down.
A drive without a crown holds water in the wheel tracks. Those tracks become ruts, and on a slope the ruts become channels that carry stone downhill after every storm.
Drainage goes in before the top stone
Water does more damage to a gravel drive than traffic does. So the ditches and pipes go in with the base, not after. A ditch line along the uphill side catches water coming off the slope. A culvert carries it under the drive wherever it needs to cross.
Where the drive meets a state road, the entrance pipe falls under an NCDOT driveway permit from the local District Engineer's office. Check before you build.
Only once the base is compacted, crowned and drained does the surface stone go on. If you want help with the whole build, ask for a free estimate or call (828) 540-6856.
The Short Version
- Strip topsoil, roots and organic material down to firm soil first.
- Grade and compact the subgrade. Soft spots under the stone become ruts in the drive.
- Use geotextile fabric on soft, wet or filled ground, where it keeps the clay out of the base.
- Build a compacted base course of ABC or crusher run in lifts, then shape a crown into it.
- Set the ditches and culverts before the surface stone goes on.
Quick Answers
What should I put down before a gravel driveway?
Strip the topsoil, then compact the subgrade. Lay geotextile fabric on soft or wet ground. Then build a compacted base of ABC or crusher run in lifts, crown it, and set the ditches and culverts. The surface stone goes last.
Do I need landscape fabric under a gravel driveway?
Not landscape fabric. That is too light. A driveway uses geotextile fabric made for roads. It pays on soft clay, wet ground and fill. On firm, dry ground it often adds little.
Can I put gravel straight on dirt?
Only on firm, compacted mineral soil with the topsoil removed, and with a real base course on it. Gravel spread on topsoil or soft clay sinks in and ruts within a season.
What goes under a gravel driveway on a slope?
The same layers, plus more attention to water. The drive is cut into the hill, the base is compacted in lifts, and the surface is sloped toward an uphill ditch with culverts at each crossing. A packing stone on top holds better than loose stone.
See our gravel driveway installation service or call (828) 540-6856.