They all look like rocks. They're all priced by the cubic yard. But road mix, crushed gravel, pea gravel, and drain rock are very different materials — and using the wrong one for your project will cost you. Pea gravel on a driveway rolls under tires and never stabilizes. Road mix in a flower bed looks awful and doesn't drain the way you need. This guide breaks down every common aggregate we deliver, what it's actually made of, and the exact applications it's right for.
Road mix — sometimes called road base, crushed base, or pit run — is a blend of crushed rock and fine material (dust and small particles) that compacts into a firm, stable surface. It's not a single rock size; it's a gradation from coarse to fine that, when compacted, interlocks and creates a surface that doesn't shift under weight.
The key characteristic: road mix is meant to compact. The fines bind it together. That's why it's the go-to material for driveways, parking areas, and any base application where stability matters. It does not drain freely — it sheds water but doesn't act as a drainage layer.
Road mix is what you want for a gravel driveway in Boise. It's cheaper than washed aggregate, it stabilizes well in Idaho's dry summers, and it handles the freeze-thaw cycle better than loose rock. Typical depth for a new driveway: 4–6 inches, compacted in two lifts.
Washed rock is crushed aggregate that's been run through a washer to remove the fines (dust and small particles). What you're left with is clean, angular rock with consistent sizing. Because the fines are gone, it doesn't compact into a solid mass the way road mix does — but it also drains exceptionally well.
Angular crushed rock interlocks and provides decent stability for foot traffic, but it won't compact the way road mix does. It's used as a drainage layer, in retaining wall cores, as a base under concrete (where you want drainage under the slab), and in some decorative applications where you want a cleaner look than road mix.
Pea gravel is small, naturally rounded stone — typically 3/8" to 5/8" in size. Unlike crushed rock, it's smooth and round rather than angular. This roundness means it does not interlock and compact. It rolls freely, shifts underfoot, and will never create a stable surface on its own.
That said, pea gravel is ideal for applications where you specifically want that loose, free-flowing texture: decorative landscaping beds, play areas (it's the safety standard for fall zones under play equipment), dog runs, and fire pit surrounds. It's comfortable to walk on barefoot, it drains well, and it looks clean in finished landscaping.
Pea gravel on a driveway will migrate under your tires and end up in your lawn within two seasons. If you like the look of smaller rock on a driveway, use a 3/4" crushed chip over a compacted road base — not pea gravel.
Drain rock is clean, washed aggregate in the 3/4" to 1.5" size range, specifically chosen for its drainage characteristics. The large void spaces between stones allow water to move freely through the layer. It's the standard material for French drains, leach fields, around foundation footings, and any situation where you need water to percolate rather than pond.
Chips are a slightly smaller version of drain rock, sometimes used decoratively or for pathway surfaces. Both drain exceptionally well and won't compact the way road mix does.
Sand is fine aggregate used in specific applications: bedding for paving stones (the layer that lets you set them precisely level), filling gaps between pavers and flagstone, mixing into concrete, or as a leveling layer for artificial turf installs. Construction sand (coarse) is different from play sand (fine, washed); make sure you're getting the right grade for your use.
Sand is not a base material on its own — it shifts. It's almost always used in combination with a compacted aggregate base below it.
Topsoil isn't aggregate — it's soil. But we deliver it alongside our other materials, and it's worth including here because people frequently confuse it with other bulk materials. Topsoil is for growing things: new lawns, garden beds, raised planters, lawn repair, and tree wells. Idaho's native soil tends to be clay-heavy and alkaline, so amending it or adding a layer of topsoil makes a significant difference for growing.
See our full guide on how much topsoil you need for different applications.
Road mix, pea gravel, drain rock, washed rock, sand, and topsoil — throughout Boise, Meridian, Nampa, Eagle, and the Treasure Valley.
| Project | Use This | Depth |
|---|---|---|
| New gravel driveway | Road Mix | 4–6 in, compacted |
| Driveway refresh | Road Mix | 2–3 in |
| Paver / patio base | Road Mix + 1 in Sand on top | 4 in base + 1 in sand |
| Under concrete slab | Washed Rock or Road Mix | 4 in |
| French drain / drainage | Drain Rock | Per trench design |
| Play area | Pea Gravel | 6–9 in |
| Decorative landscaping | Pea Gravel or Drain Rock | 2–3 in |
| Dog run | Pea Gravel | 4–6 in |
| RV / trailer pad | Road Mix | 6–8 in, compacted |
| New lawn / sod prep | Topsoil | 4–6 in |
| Garden beds | Topsoil | 6–12 in |
| Paver setting bed | Sand | 1 in over compacted base |
There's a real cost difference between materials. Road mix is typically our cheapest aggregate because it requires less processing — it comes out of the pit with a natural gradation of sizes. Pea gravel and washed rock cost more because they require washing and screening.
Don't let price push you toward the wrong material. Using pea gravel on a driveway because it's slightly cheaper than crushed rock is a decision you'll regret by spring. Use the right material for the application and you won't have to redo it.
If you're unsure between two options — say road mix vs. crushed chips for a specific surface — give us a call at (208) 906-3838. Telling us what you're doing takes 30 seconds and we can point you to the right material.
A few things specific to the Treasure Valley that affect material selection:
Need to calculate how many yards to order? Check our gravel calculator guide or use the material calculator on our delivery page.
We deliver all aggregate types throughout the Treasure Valley. Not sure what you need? Call us — we'll help you figure it out.
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