How to build a raised garden bed (and when a kit makes more sense)

Building a raised garden bed from scratch is a genuinely satisfying weekend project — and this guide walks you through it honestly: the timber to buy, the steps, the traps, and the real cost. We build thousands of these, so we'll also tell you the bits nobody mentions until they've gone wrong. And if by the end you decide the weekend is worth more than the sawdust, that's what our kits are for.

What timber should I use for a raised garden bed?

Treated pine is the workhorse — but the treatment matters. For anything growing food, use MCA treated pine (Micronised Copper Azole) — it's arsenic-free and rated for garden contact. Avoid old-style CCA-treated timber around edibles, and be careful with reclaimed sleepers of unknown history. Hardwood works too but costs more and is harder to work with. Whatever you choose, timber breathes and insulates — mix in a timber bed stays cooler in an Australian summer than in a metal one, which your roots will thank you for in January.

What size and height should I build?

Keep the bed narrow enough to reach the middle — 1.2m across is the sweet spot, any width if you can only reach one side, keep it to 75cm. Length is up to your space. Height is the decision that changes your daily experience: a 30cm border bed still means kneeling; a 50cm planter box works at seated height; an 80cm raised garden bed is true waist height — no kneeling, no bending, which is exactly why most of our customers choose it. For growing depth, 23cm suits herbs and greens, 35cm suits tomatoes, 40cm+ suits root veg — the full logic is in our bed depth guide.

How do I actually build it? The six steps

1. Cut and square the frame. Cut your sleepers or boards to length, and check the diagonals match before fixing anything — a bed that starts out of square stays out of square.
2. Fix the corners properly. Use galvanised or stainless screws (never bare steel — it rusts out in a season against damp timber) and corner posts or brackets. Wet potting mix is heavy; a full bed pushes outward on every wall, forever.
3. Add mid-span support. Any wall longer than 1.5m needs a stake or upright mid-span, or it will bow within a year.
4. Sort the base and drainage. On soil, an open base with a layer of drainage gravel works. On concrete or a deck, you need a lined base with real drainage holes and airflow underneath — this is where most DIY beds fail, and the reason our beds use a recycled plastic tub with drainage holes at every corrugation.
5. Line the walls. A breathable liner between mix and timber keeps the walls cleaner and the moisture where the roots are. Don't use solid plastic sheet — trapped water against timber is how rot starts.
6. Fill it properly. Premium potting mix, not garden soil, which compacts and drains poorly in a contained bed. Our filling guide covers the layers and the budget-friendly bulking tricks.

What does building your own actually cost?

Be honest with the tally: MCA sleepers, posts, galvanised fixings, liner, and a base solution typically land between $150 and $400 in materials for a decent-sized bed — before the potting mix, and before your weekend. That's real money and real hours, and if you enjoy the build, it's time well spent. If you'd rather be planting by lunchtime: our raised garden beds arrive as partially assembled kits Australia-wide (tools included), or fully assembled and delivered to your backyard around South East Queensland. Either way the engineering headaches above — corner strength, drainage, lining — are already solved.

What should I do once the bed is built?

Fill it (guide here), then plant to your climate, not the seed packet's — our free garden calendar matches 119 herbs, veggies and flowers to your postcode and tells you what to sow this month, plus the pests to keep an eye on.

More garden guides: common raised-bed mistakes · why raised beds work · care & maintenance · build a DIY poly tunnel

Ready to grow? Browse our raised garden beds or design yours with the garden bed builder.