Concrete Driveway Materials List: Yards, Base, Rebar, Joints
Part of the project planners: Planning a concrete patio, slab or driveway and Planning a new driveway.
A 20 × 12 ft driveway poured 5 inches thick needs 4.07 cubic yards of concrete (with 10% extra, 1 truck load), about 7.5 tons of gravel for a 6 inch base, 18 twenty-foot lengths of #4 rebar, 8 form boards and 32 ft of control joints. Here is the full list, a size chart, and the choices that change it.
The materials list
| What to buy | How much | How we worked it out |
|---|---|---|
| Concrete | 4.07 yd³ of ready-mix (1 truck load) | Driveway calculator runs our concrete calculator: 5 in thick, 10% extra. A driveway is too much to mix by hand |
| Compacted gravel base | 7.5 tons of crushed stone | Gravel calculator: 6 in deep, plus 20% because loose stone compacts |
| Rebar, #4 (1/2 in) | 18 bars of 20 ft | Rebar calculator: a grid at 18 in centers. Or 5 sheets of 5 × 10 ft wire mesh |
| Rebar chairs | About 15 | One for every 4 × 4 ft, so the steel sits mid-slab |
| Form boards | 8 boards of 8 ft (2×6) | The 64 ft perimeter, divided by 8 ft. Use 2×8 for a 6 in slab |
| Stakes | About 26 | One every 2 to 3 feet, plus the corners |
| Control joints | 32 ft to cut or tool | Panels no longer than 10 ft each way. Cut them a quarter of the slab deep |
| Isolation joint strip | 24 ft | Where the drive meets the garage slab and the sidewalk or street |
| Sealer | 1 gallon | About 250 ft² a gallon, applied after the concrete has cured for about a month |
Materials for other driveways
5 inch slab, 6 inch base, #4 rebar at 18 in centers, 10% extra concrete and 20% extra stone:
| Driveway | Area | Concrete | Truck loads | Base stone | Rebar bars |
|---|---|---|---|---|---|
| 20 × 10 ft | 200 ft² | 3.4 yd³ | 1 | 6.2 tons | 15 |
| 20 × 12 ft | 240 ft² | 4.1 yd³ | 1 | 7.5 tons | 18 |
| 24 × 12 ft | 288 ft² | 4.9 yd³ | 1 | 9.0 tons | 21 |
| 40 × 12 ft | 480 ft² | 8.1 yd³ | 1 | 14.9 tons | 35 |
| 30 × 20 ft | 600 ft² | 10.2 yd³ | 2 | 18.7 tons | 45 |
| 50 × 20 ft | 1000 ft² | 17.0 yd³ | 2 | 31.1 tons | 75 |
Enter your own length and width in the concrete driveway calculator.
How thick should it be?
| Thickness | Concrete for 20 × 12 ft | 80 lb bags | Use |
|---|---|---|---|
| 4 in | 3.26 yd³ | 147 | Cars only; the bare minimum |
| 5 in | 4.07 yd³ | 184 | Cars and light trucks: the usual choice |
| 6 in | 4.89 yd³ | 220 | Heavy trucks, RVs, delivery vehicles |
Each extra inch on this drive is about 0.81 cubic yards, which is a small part of the total cost of the job, so most people choose 5 or 6 inches for the extra strength.
Before you order
- Call 811 a few days before you dig, and ask your building department about a permit, the setback, and the rules for the apron where the drive meets the street.
- Get the base right. Dig out enough for the base and the slab together, compact the soil, then spread and compact the stone in layers of 4 inches or less.
- Plan the slope. The drive should fall at least 1/4 inch per foot so water runs off, and away from the garage.
- Order the pour. Ready-mix is on a clock, so have the forms, steel and helpers ready. Ask for a mix with the strength your area needs, often 4,000 psi, and air entrainment where it freezes.
- Check the weather. Do not pour in heavy rain or when it may freeze in the next few days.
How the job goes
- Excavate, compact the soil, and place and compact the gravel base.
- Set the forms on stakes at the right height and slope, and check them with string and a level.
- Place the rebar or mesh on chairs, keeping it a few inches in from the edges.
- Pour, screed the surface level, float it, and edge the slab.
- Broom the surface for grip, and cut or tool the control joints.
- Cure it for a week by keeping it damp or covered. Keep cars off for about a week and heavy trucks for a month.
Mistakes that cost people money
- A thin or uncompacted base, which lets the slab settle and crack.
- Skipping control joints. Concrete shrinks as it cures, and joints decide where it cracks.
- Adding water to make the concrete easier to place. It weakens the slab.
- Ordering too little. A second delivery leaves a cold joint, so always allow 5 to 10% extra.
- Using de-icing salts in the first winter, which can scale the surface of new concrete.
See also the concrete patio materials list, the bags of concrete guide and the gravel driveway materials list if you would rather not pour. Estimates only: check your local code, and follow the product labels.
Frequently asked questions
How much concrete do I need for a 20x12 driveway?
A 20 × 12 ft driveway 5 inches thick needs 3.70 cubic yards before waste and 4.07 cubic yards with 10% extra. At 4 inches it is 3.26 cubic yards, and at 6 inches 4.89.
How much does a concrete driveway weigh?
Concrete weighs about 4,050 pounds per cubic yard, so 4.07 cubic yards weighs about 16,500 pounds. The ground and base have to carry that, which is why the base matters.
How thick should a concrete driveway be?
Four inches is the minimum for cars, 5 inches suits cars and light trucks, and 6 inches is for heavy trucks, RVs or delivery vehicles. Your local code can set a minimum.
How many truck loads of concrete do I need?
A ready-mix truck carries up to 10 cubic yards, so a 20 × 12 ft drive at 5 inches needs 1 load. Small orders often carry a short-load fee, so ask the plant.
How far apart should control joints be?
About two to three times the slab thickness in feet: 10 feet for a 5 inch slab. A 20 × 12 ft drive then has 32 ft of joints to cut or tool.
More guides
Tools & materials for this project
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and follow local building codes for anything structural.