Gravel Depth Guide: How Deep for Driveways, Paths, and More
How deep should gravel be for a driveway, path, French drain, paver base, or shed pad? A practical depth reference with the reasoning behind each.
Depth is the input that wastes the most money when guessed. Order an inch too thin and your driveway potholes; order an inch too deep and you've paid for a yard of stone you'll never see again. This guide gives you a quick reference for every common project, then explains the reasoning so you can adjust for your site.
Quick depth reference
| Project | Depth (compacted) | Material |
|---|---|---|
| Decorative beds & ground cover | 2–3 in | Pea gravel, river rock, lava |
| Walking path | 2–3 in | Pea gravel or DG over base |
| Patio under pavers | 4 in base + 1 in sand | CA6 + concrete sand |
| Light vehicle driveway | 4 in base + 2 in top = 6 in | CA6 + #57 |
| Heavy / RV / truck driveway | 6 in base + 2–3 in top = 8–9 in | CA6 + #57 |
| French drain (around 4" pipe) | 12 in vertical (full trench) | #57 stone |
| Shed or outbuilding pad | 4–6 in | #57 or CA6 |
| Drainage behind retaining wall | 12 in column | #57 stone |
| Around a pool / drainage | 4–6 in | #57 or river rock |
| Aquarium substrate (freshwater) | 1–2 in | Washed pea gravel or specialty |
| Aquarium (planted) | 2–3 in | Specialty planted substrate |
Driveway depth
A passenger-vehicle driveway needs 4 inches of dense-grade base + 2 inches of top course. The base does the structural work; the top is wear surface and aesthetics. This isn't a single layer of 6-inch gravel — the two layers are different materials with different jobs.
For RVs, work trucks, or soft soil (clay, organic), step up to 6 inches of base + 2–3 inches of top. If your soil is unusually soft (peat, recent fill), the right answer isn't more gravel — it's geotextile fabric over the soil before you put any gravel down. Fabric stops the gravel from migrating into the mud, which is how soft soil eats driveways.
Paver patio depth
Pavers fail in three ways: settlement (soft base), heave (poor drainage), and joint erosion (no edge restraint). Depth fixes settlement.
- Pedestrian patio: 4 inches of compacted CA6, then 1 inch of concrete sand bedding, then pavers. Total excavation = 4 + 1 + paver thickness.
- Vehicular patio (driveway pavers): 6 inches of compacted CA6, then 1 inch of sand, then pavers.
- In freeze-thaw climates: add 2 inches to the base depth — frost heaves a thin base.
The CA6 must be compacted in 2-inch lifts with a plate compactor. Dumping 4 inches loose and tamping the surface only compacts the top inch — the bottom 3 inches stay fluffy and the patio settles.
Path and walkway depth
For a casual garden path, 2–3 inches of pea gravel or decomposed granite over compacted dirt is fine. For a path that gets heavy use or rolls a wheelbarrow, build it like a mini-driveway: 2 inches of CA6 base + 1–2 inches of pea gravel top, with edging on both sides.
More than 3 inches of pea gravel makes walking harder, not easier — your foot sinks and the stones shift. The depth that feels best is shallower than people think.
French drain depth
A French drain is a perforated pipe surrounded by free-draining stone, with fabric around the whole assembly. Standard build:
- Trench depth: 18–24 inches (deeper for foundation drains)
- Trench width: 12 inches
- Stone: 6 inches below the pipe + pipe + 6 inches over the pipe
- So the gravel column is approximately 12 inches tall (varies with pipe size)
- Pipe slope: 1% (1 inch of fall per 8 ft) toward daylight
Use #57 stone — angular, no fines, drains free. Never use anything with fines (no CA6) inside a French drain; the fines clog the perforations.
Shed and outbuilding pad depth
For a shed up to 12 × 16 ft, a 4-inch compacted base of #57 stone is plenty — contained by pressure-treated 4×4 perimeter timbers. For larger outbuildings or any structure with a concrete floor, step up to 6 inches of CA6 compacted in lifts.
Always extend the gravel pad 6–12 inches beyond the footprint of the building so rain dripping off the eaves lands on stone instead of mud.
Decorative bed depth
The most common over-ordering mistake. Most decorative gravel beds need only 2 inches on top of landscape fabric. Going deeper costs more, doesn't suppress weeds any better (the fabric does that), and makes the bed harder to plant into later if you change your mind.
Mulch-substitute lava rock can go a touch deeper — 2.5 to 3 inches — because it's so light that a thinner layer doesn't look right.
Compaction adjustment
Gravel settles when compacted. Loose dump from the truck is roughly 15–20% taller than the same gravel after a plate-compactor pass. So when you order:
- Dense-grade bases (CA6, ABC, 21AA): order at 1.2× your finished depth (e.g., for 4 inches finished, order enough for 4.8 inches loose).
- Open-grade stone (#57, #4): roughly 1.1×. Open-grade stones don't compact much, but they settle a bit under traffic.
- Decorative gravels (pea, river): no adjustment needed — they don't compact and you don't want them to.
The 10% buffer that the calculator applies by default already covers most of this for decorative and open-grade applications. Bump it to 15% for any project where you're running a compactor.