Class 2 Aggregate Base: Size, Weight and How Many Tons
Class 2 aggregate base (often labeled Class 2 AB, Class 2 road base or Class 2 base rock) is a dense-graded crushed stone with fines that packs into a firm structural layer. It is a standard base under asphalt, concrete and pavers in regions that follow Caltrans-style specs, and yards elsewhere sell similar products under local names. This guide covers what Class 2 is, how it compares to crusher run and other bases, how deep to place it, how much a yard weighs and how many tons to order.
Open the base calculator →What Class 2 aggregate base is
Aggregate base is crushed rock graded so larger stones, sand-size particles and dust all sit in the mix. The fines help the stone lock when it is wetted and compacted. “Class 2” points to a published gradation and quality rules rather than a single rock type. Caltrans Class 2 aggregate base is one widely referenced specification; your state DOT, city or project plans may cite Class 2 AB, Class 2 base or an equivalent.
Ask the yard what top size it stocks (often around 1 inch or 1 1/2 inch), whether the pile meets a named Class 2 or AB gradation, and whether recycled concrete is allowed in that product. A “road base” pile that is only loosely similar is not the same as a ticketed Class 2 load when a paving detail requires the spec.
Class 2 vs crusher run, ABC and road base
Dense bases with fines show up under many regional names. They are cousins, not identical products:
- Class 2 AB / Class 2 road base — Caltrans-style dense aggregate base used under pavement and as compacted driveway base.
- Crusher run — quarry mix of stone and dust; see crusher run driveway.
- Road base — generic label; our what is road base guide explains the range.
- ABC gravel — aggregate base course common in parts of the Southeast; see ABC gravel.
- 2A modified — PennDOT-style dense base; see 2A modified stone.
- Dense grade aggregate (DGA) — another regional dense base; see dense grade aggregate driveway.
If plans say Class 2, order a product the yard will ticket as meeting that class. If you only need a firm gravel driveway and no spec is listed, any well-graded dense base the yard recommends for driveways may work — still ask for the tons-per-yard figure and the top size.
Where Class 2 is used
- Under asphalt or concrete as the compacted structural base.
- Under pavers beneath the bedding sand, when the detail calls for aggregate base.
- As a gravel driveway or lane surface when you want a packed, gray stone road rather than clean drain rock.
- Shoulders, pads and equipment yards that need a firm, load-bearing layer.
Class 2 is not a French-drain stone. For open drainage, use clean stone such as #57 stone and keep the dense base for structural layers.
How deep to place it
- Top-up over a firm existing base: about 2 to 3 inches compacted.
- New light-use driveway on firm soil: often about 4 to 6 inches compacted total.
- Soft soil, clay or heavier trucks: 6 to 8 inches or more, built in lifts, sometimes over geotextile fabric.
- Under asphalt or concrete: follow the paving or permit detail; residential jobs often land in a similar 4 to 8 inch compacted range for the stone base.
These are planning ranges, not a substitute for a plan detail or a contractor who has seen your subgrade. Soft spots and poor drainage usually need more thickness or a different section.
How much a yard weighs
Dense aggregate bases are heavy. For planning, many people use about 1.3 to 1.5 tons per loose cubic yard and then confirm with the supplier. Moisture, rock type and how dusty the pile is all move the number. Our gravel weight per yard overview covers typical ranges across stone types. Always prefer the yard’s own tons-per-yard value on the ticket.
How many tons to order
Measure length and width in feet and finished depth in inches, then:
- Cubic yards = length × width × depth in inches ÷ 324
- Tons ≈ cubic yards × the supplier’s tons-per-yard figure (about 1.4 is a middle planning value if you do not have one yet)
- Add 10 to 15 percent for compaction and uneven ground
| Depth | Approx. area per ton (at 1.4 t/yd) | Tons per 100 sq ft |
|---|---|---|
| 3 inches | about 77 sq ft | about 1.3 |
| 4 inches | about 58 sq ft | about 1.7 |
| 6 inches | about 39 sq ft | about 2.6 |
| 8 inches | about 29 sq ft | about 3.5 |
Example: a driveway 12 feet wide and 40 feet long at 6 inches is 12 × 40 × 6 ÷ 324 ≈ 8.9 cubic yards. At 1.4 tons per yard that is about 12.5 tons; with 15 percent extra, order about 14 to 15 tons. The base calculator handles other shapes, and how many tons of gravel in a dump truck helps turn tons into deliveries.
How to place and compact it
- Strip sod and soft topsoil so the base sits on firm subgrade.
- Grade for drainage before and after stone. Water that sits in the base softens it.
- Place in lifts of about 2 to 4 inches and compact each lift. See compacting a gravel base in lifts.
- Dampen the stone so fines knit; bone-dry or soup-wet material packs poorly.
- Use a plate compactor or roller. Hand raking alone will not lock Class 2.
Buying tips
- Ask for the spec name on the ticket (Class 2 AB, Class 2 base, or the local equivalent).
- Confirm virgin vs recycled if the project limits recycled concrete content.
- Look at the pile for oversized rock, mud balls and trash before you accept the load.
- Plan the drop on firm ground clear of septic lids, soft lawn and low wires.
Questions people ask
What is Class 2 aggregate base?
Class 2 aggregate base (often called Class 2 AB or Class 2 road base) is a dense-graded crushed rock with fines, specified so it packs into a firm structural layer under pavement, pavers or a gravel surface. Caltrans publishes a common Class 2 AB gradation; other agencies use similar names.
How much does Class 2 base weigh per yard?
Dense aggregate bases usually land around 1.3 to 1.5 tons per loose cubic yard, depending on rock type and moisture. Ask your supplier for the ticket weight and use that number when you convert area into tons.
How deep should Class 2 base be for a driveway?
Light residential use on firm soil often uses about 4 to 6 inches compacted. Soft ground, clay or heavier trucks may need 6 to 8 inches or more, placed and compacted in lifts. Follow any plan or permit detail when one exists.
Is Class 2 the same as crusher run or ABC?
They behave similarly as dense bases with fines, but the names and gradations are regional. Class 2 AB is a Caltrans-style product; crusher run, DGA, ABC, 2A and Item 4 are related products under other specs. Ask the yard which spec it meets.
Can I use Class 2 as the finished driveway surface?
Yes as a packed gravel-style surface, with the usual need for crowning, grading and top-ups. Many jobs use Class 2 as the base under asphalt, concrete or pavers rather than as the wearing course.
Do I need fabric under Class 2 base?
On soft clay, wet spots or mixed soils, a geotextile under the first stone lift can keep fines from pumping into the base. On firm, well-drained subgrade it is often optional. A contractor who has seen your soil can advise.
Related guides
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