Raised Garden Bed Materials List: Soil, Lumber and Irrigation
Part of the project planner: Planning a new lawn and garden beds.
Two 4 × 8 ft raised beds filled 12 inches deep need 70 cubic feet of soil (2.6 cubic yards, with 10% for settling), 6 boards of 8 ft for the frames, and a way to water them. Soil is by far the biggest cost, so it is worth deciding early between bagged and bulk.
The materials list (two 4 × 8 ft beds)
| What to buy | How much | How we worked it out |
|---|---|---|
| Soil mix | 70 ft³, or 2.6 yd³ | Raised bed soil calculator: 12 in deep, 10% extra for settling. In bags of 2 ft³ that is 36 bags |
| Frame lumber (2×12, 8 ft) | 6 boards | Each bed is 24 ft around: two 8 ft sides and two 4 ft ends, which three 8 ft boards make if you cut one in half. A 2×12 gives about 11 inches of height |
| Corner posts or brackets | 8 (4 per bed) | Untreated or garden-safe lumber such as cedar lasts longest. Use galvanized or stainless screws |
| Hardware cloth (optional) | Two pieces of 4 × 8 ft | Stapled under the bed to keep out gophers and moles |
| Landscape fabric or cardboard | About 77 ft² | Under the soil, to smother grass and weeds |
| Drip irrigation kit | 1 kit | A drip line or soaker hose on a timer waters at the roots and wastes less than a sprinkler |
| Path mulch (example) | 0.56 yd³ | Mulch calculator: for 60 ft² of paths at 3 in deep |
Soil needed by bed size
One bed of each size, 12 in deep, with 10% for settling:
| Bed size | Soil | Bags of 2 ft³ | Frame boards (8 ft) |
|---|---|---|---|
| 4 × 4 ft | 17.6 ft³ (0.65 yd³) | 9 | 2 |
| 3 × 6 ft | 19.8 ft³ (0.73 yd³) | 10 | 3 |
| 4 × 8 ft | 35.2 ft³ (1.30 yd³) | 18 | 3 |
| 4 × 12 ft | 52.8 ft³ (1.96 yd³) | 27 | 4 |
Bags or bulk?
One 4 × 8 ft bed at this depth takes 1.3 cubic yards, which is 18 bags of 2 ft³. Past about 20 to 30 cubic feet, bulk soil delivered by the yard is usually much cheaper, so for two beds it is worth getting a quote. Ask for a screened mix suitable for vegetables, and check what it contains. A common recipe is equal parts compost, peat moss or coir, and vermiculite, or a mix of topsoil and compost for large beds. The raised bed soil guide covers mixes and ways to use less soil.
Building and filling
- Choose a spot with 6 to 8 hours of sun, close to a water source, and level it.
- Cut the boards, screw the frame together at the corners, and set it in place. Keep the bed no wider than 4 ft so you can reach the middle from both sides.
- Lay cardboard, fabric or hardware cloth on the ground, then fill with soil to about an inch below the rim.
- Water it well, let it settle, and top up. Lay the drip line before you plant.
- Mulch the surface lightly, and keep topping the soil up with compost each spring.
Spacing for what you plant is in the plant spacing calculator. Estimates only.
Frequently asked questions
How much soil do I need for two 4x8 raised beds?
70 cubic feet (2.6 cubic yards) at 12 inches deep, with 10% extra for settling. In bags of 2 ft³ that is 36 bags, so bulk delivery is usually cheaper.
How many boards do I need for a 4x8 raised bed?
Three 8 ft boards make one frame that is one board high: two 8 ft sides, and one board cut in half for the 4 ft ends. A 2×12 gives about 11 inches of height.
How deep should a raised bed be?
Eight to twelve inches suits most vegetables, 6 inches is enough for lettuce and herbs over loosened ground, and 15 to 18 inches suits deep-rooted crops or beds built on concrete.
What should I fill a raised bed with?
A mix of compost and topsoil, or equal parts compost, peat moss or coir, and vermiculite. Choose a dark, crumbly screened mix made for vegetable gardens, and top it up with compost each year.
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.