Why Build a Raised Garden Bed?

Raised beds offer better drainage, warmer soil (plants grow faster), control over soil quality, fewer weeds from the ground, easier access (less bending), and defined growing spaces. They are particularly valuable in areas with poor native soil, clay, or compacted ground.

Materials for a Basic Raised Bed

  • Timber: Treated pine sleepers (100x200mm cross-section) are the most common and cost-effective. Hardwood sleepers last longer but cost more. Railway sleepers look great but may contain old chemicals — use new untreated hardwood or treated pine for edible gardens. Avoid CCA-treated timber (greenish colour) in vegetable beds — use H4 ground-contact treated pine instead.
  • Hardware: 150mm galvanised carriage bolts and nuts, or timber screws 100mm+
  • Weed matting: Lay on the base to suppress weeds from below (optional but helpful)
  • Soil mix: See below

Standard Dimensions

Width: maximum 1.2m (so you can reach the centre from either side without stepping in). Length: as long as you like — 1.2m and 2.4m are standard sleeper lengths. Height: 200–400mm is comfortable (one or two sleepers stacked). Taller beds need more fill but are easier on your back.

Step-by-Step Build

  1. 1

    Choose and prepare the site

    Pick a spot with at least 6 hours of sun for vegetables. Level the ground roughly. Mark out the bed dimensions with stakes and string.

  2. 2

    Cut sleepers to length

    Cut two pieces to the bed width and two to the bed length. A circular saw or handsaw handles this. Hardware stores will cut to length for a small fee.

  3. 3

    Assemble the frame

    Lay the first layer of sleepers in a rectangle. Pre-drill pilot holes at the corners to prevent splitting. Drive 100mm screws through the end pieces into the side pieces (butted joints), or use metal L-brackets at each corner for added strength. Stack the second layer, alternating the corner joins like brickwork for strength. Drill and bolt through both layers at each corner.

  4. 4

    Lay weed matting on the base

    Cut weed matting to fit the base and lay it down. This suppresses weeds from below while allowing water to drain through.

  5. 5

    Fill with quality soil mix

    A good raised bed mix: 60% quality topsoil or garden soil, 30% compost (organic matter feeds the plants), 10% coarse sand or perlite (improves drainage). Fill to within 3–5cm of the top. The mix will settle over the first few weeks — top up as needed. Water thoroughly before planting.

Cost estimateA 1.2m x 2.4m x 400mm high raised bed costs approximately $80–150 in materials (timber, bolts, soil mix). Pre-built raised bed kits from garden centres or Bunnings are convenient but often more expensive for the size. Building from sleepers gives the most space per dollar.

Frequently Asked Questions

Almost any vegetable, herb or flower. Raised beds are particularly good for: leafy greens (lettuce, spinach, silverbeet), root vegetables (carrots, radishes, beetroot — the deep loose soil is ideal), tomatoes, zucchini, strawberries, herbs. Larger plants like pumpkins and corn will grow but quickly take over — grow them in-ground and save the raised bed for more intensive plantings.
No — raised beds drain naturally as excess water flows over the edges and down through the soil. Unlike pots, they are open at the bottom. The weed matting base is permeable and does not impede drainage. If water is pooling significantly, the soil mix may have too much clay — add more compost and coarse sand.