Road Base Types: Which to Choose

Crusher run is the workhorse road base for most jobs. It is a dense-graded blend of crushed stone and stone fines, straight from the crusher with nothing screened out. The name changes by region. In many areas it is called ABC, which stands for aggregate base course. In others it is crush-and-run or dense-graded aggregate. These names point to the same kind of material.

The blend is what makes it work. It runs from larger crushed stone, often up to about an inch, down to a dust of fines. The fines fill the gaps between the stones. When you compact the blend, the stones lock against each other and the fines bind them. The result is a hard, tight layer that carries load and sheds water.

Crusher run is the default base under driveways, roads, parking pads, and slabs. It compacts into a stable sub-base that resists rutting. It drains well enough for most sites when it is graded to a slope.

Order crusher run by the local name your supplier uses. Ask for the top size and confirm it is a dense-graded blend with fines, not a washed single-size stone. Place it in lifts and compact each lift. Enter your finished compacted depth into the road base calculator to size the load.

Number 57 stone and dense-graded base look similar in the pile, but they behave in opposite ways. Knowing the difference keeps you from ordering a base that will not lock.

Number 57 stone is a clean, single-size crushed stone, roughly three-quarters of an inch to an inch. The fines are washed out, so the stones do not pack tight against each other. This open structure drains fast and stays loose. It does not compact into a hard layer, because there are no fines to bind it. Water and small stones can shift within it.

Dense-graded base is the opposite. It carries the full range of sizes, from top stone down to fines. The fines fill the voids, so the blend compacts into a firm, stable sub-base. This is the material you want under a driveway, a slab, or a paver patio that must not shift.

Use number 57 where free drainage matters more than a hard surface. It suits French drains, pipe bedding, and a drainage layer beneath a structure. It also works as a clean, loose fill that will not hold water.

Use dense-graded base where the layer must carry load and stay put. If you need a compacted sub-base, do not substitute number 57 stone. Match the material to the job, then size the amount with the calculator.

Recycled concrete base is crushed from old concrete, such as broken slabs, curbs, and demolition rubble. The concrete is crushed and screened to a dense-graded blend, much like crusher run. Suppliers may call it recycled concrete aggregate or crushed concrete base.

It compacts into a hard, stable sub-base and carries load much like quarried stone. The blend of crushed pieces and fines locks together when packed. Many driveways and parking pads use it as their base layer. It is often easier to source in urban areas, where demolition supplies it.

Recycled concrete base has a trait worth knowing. The fresh crushed concrete can set up firm over time, almost like a weak cement, as the fines cure. This can make a very hard base. It can also raise the pH of runoff, so keep it clear of acid-loving plants and sensitive drainage.

The blend may carry stray bits of rebar wire, brick, or asphalt, depending on the source. Ask your supplier how clean their product is and whether it is screened. For most base work under a driveway or a slab, a clean recycled concrete base is a sound, dense-graded choice. Confirm the top size, place it in lifts, compact each lift, and size the load with the calculator.

Stone dust, also called screenings, is the fine material screened off during crushing. It runs from a coarse sand down to a powder, with little or no larger stone. It is not a structural base on its own, but it plays a key role as a top course over a compacted base.

Use screenings as a thin setting layer above a dense-graded base. On a paver patio or a stone walkway, you compact the road base first, then spread a shallow, even layer of screenings. The screenings give a smooth, level bed that you can screed flat. The pavers or stones set into this fine layer.

Screenings also make a firm, tight surface on a path. Spread over a compacted base and packed, they form a hard walking surface that sheds water. This suits garden paths and light foot traffic where a smooth top matters.

Do not use screenings as the whole base under a load. Without the larger stone, the fine layer lacks the strength to carry heavy weight and can hold water. Keep it thin and keep it on top of a proper compacted base. Size the base layer with the calculator, then add the screenings as a shallow top course.

The right base type follows the job. Start from the load the surface will carry and the finish that goes on top. Then pick the blend and the depth to match.

For a residential driveway, a dense-graded base is the standard choice. Crusher run, ABC, or a clean recycled concrete base all compact into a firm sub-base. A common depth is 4 to 6 inches compacted for cars and light trucks. This base spreads the load and resists rutting.

For a paver patio, build in two parts. Lay a compacted dense-graded base for strength, then a thin course of screenings as the setting bed. The base carries the load and the screenings give a smooth, level surface for the pavers. This keeps the pavers from shifting or settling unevenly.

For a heavy load, such as an RV pad, a truck drive, or an equipment area, add depth. Use a dense-graded base at 6 to 8 inches compacted, or more on soft ground. A deeper base bridges a weak subgrade and carries the extra weight without sinking.

Whatever the job, place the base in compacted lifts and grade it to a slope for drainage. Enter your area and finished compacted depth into the road base calculator. It reports the cubic yards and the tons to buy.