How to Build a Raised Bed Step by Step

What size should your raised bed be?

Width comes down to how far you can comfortably reach without stepping into the soil and compacting it. If you can only work from one side — against a fence or a house wall, say — keep the width to 75–80 cm (30 in) at most. If you can work from both long sides, 100–120 cm (40–48 in) is fine, since you'll never need to reach more than 50–60 cm (20–24 in) in from either edge.

Height is the detail most people underestimate. A shallow bed at 20–25 cm (8–10 in) works fine for lettuce and herbs, but carrots, parsnips and potatoes want deeper soil to stretch down into. Going with 40–50 cm (16–20 in) gives both better root space and a working height that's noticeably easier on your back — plenty of gardeners choose that height purely to avoid bending as far when weeding and harvesting.

Length is more flexible, but boards longer than about 2.4–3 m (8–10 ft) start to bow outward under soil pressure unless you add bracing partway along. If you want a really long growing area, it's usually simpler and more stable to build two shorter beds side by side than one long one.

Which wood should you choose?

This is the one question gardeners genuinely disagree on, and it's worth understanding both sides before you buy lumber.

Pressure-treated lumber is the most common choice at any hardware store. Modern treatment relies on copper-based compounds rather than the arsenic-based formulas phased out decades ago, and treated lumber holds up in direct soil contact for ten to twenty years or more. Most building codes and agricultural extensions consider it acceptable for food-growing beds, and it's the option most people choose simply because it's affordable, widely available and long-lasting.

Some organic growers take a more cautious stance and avoid treated lumber altogether, on the reasoning that copper compounds still leach into the soil in small amounts over time. Their alternative is untreated naturally rot-resistant wood — cedar, oak or dense-grained heartwood pine — sometimes with the interior surface charred to slow decay, or finished with plain linseed oil instead of a chemical wood preservative. The trade-off is a shorter lifespan unless you lift the bed and let it dry out over winter, and a higher price for cedar and oak compared with treated pine.

There's no universally correct answer here — it comes down to how much weight you put on avoiding any leaching at all versus how much maintenance and cost you're willing to accept. If you're growing root vegetables that sit in direct contact with the interior wall for months, like carrots and parsnips, it's a reasonable trade-off to lean toward untreated wood, or at least line the interior so soil doesn't rest directly against the boards all season.

Good to know. Whichever wood you pick, a bed lasts longer if you staple a thin plastic liner or landscape fabric between the soil and the inside of the walls. It slows moisture and soil contact against the wood without affecting the growing conditions, and it works equally well with treated or untreated lumber.

Reclaimed pallets or dimensional lumber — which should you use?

The classic image of a raised bed built from actual shipping pallets is still a common DIY route, and it can absolutely work — but there are a couple of things worth knowing before you drag home a stack of free pallets from behind a store.

The obvious upside is cost. Discarded pallets are often free or nearly free, and standard pallet dimensions make it easy to build to round numbers without much extra cutting. A couple of free pallets rarely add up to enough lumber for a full-size bed, so expect to need more of them than you'd initially guess, and expect some inconsistency in thickness and quality between different pallets. The downside is also that you rarely know for certain what the wood has been treated with. Most pallets are heat-treated (stamped "HT"), which is a completely harmless process, but some older or imported pallets may have been chemically fumigated with compounds that have no business anywhere near soil you plan to grow food in. Check the IPPC stamp on the pallet — "HT" means heat-treated and fine to use, while "MB" (methyl bromide) means you should not build a growing bed out of it.

Dimensional lumber from a hardware store or lumber yard costs more but gives you full control: you know exactly what it's been treated with, you're driving your own screws instead of prying apart pallet blocks, and you can cut it to the exact dimensions you actually want instead of designing around whatever pallets you happened to find. If this is your first raised bed and you want certainty about what's touching your soil, new lumber is simply the more straightforward choice.

What do you need — tools and materials?

Beyond the lumber itself, basic carpentry tools get you most of the way there. You'll need boards for the walls, corner posts at least 4×4 cm (2×2 in) — thicker for extra-sturdy beds — rust-resistant or hot-dip galvanized screws at least 6 cm (2.5 in) long, a drill/driver, a saw if the lumber yard doesn't cut it to length for you, a level and a tape measure.

• Wall boards, cut to your chosen length
• Corner posts, 4×4 cm (2×2 in) or 7×7 cm (3×3 in) for extra-stable beds
• Screws, at least 6 cm (2.5 in), stainless or hot-dip galvanized
• Drill/driver with a bit matched to your screws
• Level
• Tape measure
• Landscape fabric or hardware cloth for the bottom (optional, see below)
• Staple gun if you're lining the interior with plastic film

How to build a raised bed step by step

1. Decide on dimensions and sketch it out. Work out width, length and height before you buy lumber, so you're not stuck with the wrong board lengths at home.
2. Cut the lumber. Cut the wall boards to length and the corner posts to the bed's final height, plus a few extra centimeters if you want to drive them into the ground for stability.
3. Assemble one short side. Attach two or three boards to a corner post at each end, one screw per board and post is enough if the screw is thick enough to hold.
4. Repeat for the other short side. Make sure the boards line up at the same height as the first side.
5. Stand the short sides up and connect the long sides. Screw the long boards into the same corner posts, one side at a time, checking with a level that everything is square before you tighten everything down.
6. Add a mid-span brace if needed. For beds longer than about 2 m (6–7 ft), add an extra post halfway along each long side to stop the wall from bowing outward under soil pressure.
7. Check the diagonals. Measure corner to corner across both diagonals. If the two measurements match, the frame is square.
8. Move the bed into position. Move or carry the frame to its final spot before filling it — a filled bed weighs several hundred kilograms and can't be relocated afterward.

Should you line the bottom with fabric or mesh?

A raised bed normally has no bottom at all, and that's actually a benefit — it allows free drainage and lets earthworms and soil life move freely between the bed and the ground underneath.

If you're dealing with persistent weeds or grass creeping up from below, a layer of cardboard or several sheets of newspaper laid directly on the ground is a simple way to smother it for the first year without sealing out worms and soil life the way a solid plastic barrier would. The cardboard breaks down naturally over the season.

If burrowing pests like voles or gophers are the problem instead, a fine-gauge stainless or galvanized wire mesh (hardware cloth) across the bottom is really the only solution that actually works. Staple the mesh to the inside bottom edge of the walls before you fill the bed with soil.

Where should you place a raised bed?

Most vegetables want at least six hours of direct sun a day, so an open, sunny stretch of yard almost always beats a shaded spot near the house. At the same time, avoid extremely exposed, windy locations — hard wind dries soil out faster and can snap tall plants like tomatoes and beans.

Think about distance to a water source too. A bed sitting far from a hose or rain barrel is easy to neglect simply because it's a hassle to haul watering cans out there every day during a dry spell.

With multiple beds, leave at least 60–90 cm (24–36 in) between them so a wheelbarrow fits through, and keep in mind that a taller bed casts more shade on a neighboring bed to its north as the sun sits lower later in the season.

A common beginner mistake is building one large bed when two or three smaller ones would have been both cheaper in lumber and easier to manage. Smaller beds are easier to cover with frost fabric on a cold night, easier to rotate crops through year to year, and you skip the extra mid-span brace a really large bed needs to keep from bowing.

How to fill a raised bed with soil

Filling an entire raised bed with nothing but purchased planting soil gets expensive fast, and it's rarely necessary anyway. A well-tested approach is to build the fill up in layers, similar to lasagna gardening:

1. Bottom layer, 10–15 cm (4–6 in). Coarser material like branches, bark or half-finished compost. It takes up volume cheaply and slowly breaks down into nutrients over time.
2. Middle layer, 10–15 cm (4–6 in). Finished compost or well-aged manure, ideally mixed with some of the existing ground soil if you dug any up before setting the bed in place.
3. Top layer, 20–25 cm (8–10 in). Good planting or vegetable soil, ideally blended with more compost to give it decent structure and nutrients right from the start.

The fill settles noticeably during the first year as the bottom layer breaks down, so plan on topping up with a thin layer of fresh soil or compost every spring.

Maintenance year after year

Scrape soil away from direct contact with the wood walls in fall if you can, especially with untreated lumber. That reduces how long the wood sits damp and noticeably extends its lifespan over several seasons.

Check the screws once a year — wood that dries and dampens repeatedly shifts slightly, and a screw that's loosened is quick to retighten before it becomes a bigger problem. Replace individual rotted boards as they fail rather than waiting until the whole bed needs rebuilding.

Top up with compost or fresh soil every spring to make up for settling and the nutrients last season's crop used up. If you want to know what actually does well in a finished bed, our guide to growing vegetables in containers and beds and our guide to garden soil types cover what to plant and how to keep the soil healthy season after season.

Common mistake. A lot of people fill the whole bed with nothing but bagged topsoil and then wonder why it's sunk several inches by the end of the first summer. Without a bottom layer of coarser, slow-breakdown material, pure topsoil settles unusually far, since it's already fine-textured and compacts on its own.

Do you need a cover to keep out birds and cats?

A simple cover made of chicken wire or bird netting stretched over a lightweight wooden frame makes a real difference if neighborhood cats treat freshly filled, loose soil as an inviting litter box, or if birds keep digging up newly sown seeds before they've had a chance to sprout.

Build the frame from the same light furring strips you might use for the mid-span brace, cover it with netting or garden fabric, and keep it light enough to lift off easily for watering and general care. A loose-fitting cover works fine for most home setups, but if you want more permanence, simple hinges along one edge let it swing open like a lid.

Protection matters most in the first few weeks after sowing, before seedlings are more than a couple of centimeters tall. Once crops are established, most problems with both cats and birds tend to sort themselves out.

How much does it cost to build a raised bed?

Lumber is by far the biggest single cost, and the price gap between options is bigger than most people expect before they start shopping. Pressure-treated pine in thick dimensions usually comes in cheapest per linear foot, while cedar and oak often cost two to three times as much for the same amount of wood — a difference that adds up fast on a large bed that needs well over 30 meters (100 feet) of boards.

Screws, corner posts and any landscape fabric or mesh make up a relatively small share of the total cost, but don't cut corners there to save a few dollars. Thin screws that rust or work loose within a couple of years end up costing more in hassle than they saved in price.

Soil is often the cost people underestimate most. Filling a large bed entirely with bagged planting soil can easily come out more expensive than the lumber itself. Building the fill up in layers with coarser material and compost at the bottom, following the approach earlier in this guide, keeps both the cost and the total volume of soil you need to buy well under control.

Common mistakes

• Building it too wide. A bed wider than 120 cm (48 in) with access from both sides forces you to step into the soil to reach the middle, compacting it unnecessarily.
• Skipping the mid-span brace on long beds. Without an extra post halfway along a long wall, the boards slowly bow outward from soil pressure within a couple of seasons.
• Using thin, flimsy screws. Short or thin screws work loose quickly as the wood moves with moisture and drying. Go with thick screws at least 6 cm (2.5 in) long.
• Filling straight with bagged topsoil. Without a coarser bottom layer, the fill settles considerably more than expected.
• Placing it in shade because it happens to fit next to a path. Most vegetables yield noticeably worse at four hours of sun compared with six to eight.
• Not checking the diagonals while building. A frame built out of square is harder to fit lids or covers to later and looks skewed even after it's filled.

Frequently asked questions

Does a raised bed have to be built from actual shipping pallets?
No. The style is loosely associated with pallet-style wood construction in some regions, but today it just refers to any bottomless, box-shaped growing bed regardless of what lumber it's built from or whether it uses reclaimed pallet wood at all.

Is pressure-treated lumber dangerous for the vegetables growing in it?
Modern lumber treated to current standards uses copper-based compounds and is widely accepted as safe for food-growing beds, but some leaching does happen over time, especially in the first few years. If you want to be extra cautious, line the interior with a thin plastic film between the soil and the wood, or choose untreated cedar or oak instead.

How much soil do I need for a raised bed?
A bed measuring 120x80x40 cm (4×2.6×1.3 ft) holds roughly 380 liters (100 gallons), though since the bottom 10–15 cm (4–6 in) is typically filled with coarser material rather than pure soil, actual soil needed is somewhat less. As a rough estimate, multiply width by length by height in meters, then by a thousand, for total liters.

Can I build a raised bed directly on grass or pavement?
On grass, absolutely — lay down cardboard or newspaper first to smother the grass before filling with soil. On pavement or other hard surfaces, the bed needs to be considerably deeper, at least 40–50 cm (16–20 in), since roots can't reach down into any ground soil at all.

How long does an untreated pine bed actually last?
Plan on three to seven years in constant soil contact. Lifting the bed and letting it dry somewhere sheltered over winter, or scraping soil away from the walls in fall, can add a few more years to that.

Do I need drainage holes in the bottom?
No, if the bed sits directly on soil or grass with no bottom, water already drains away through the ground underneath. If you've installed a solid bottom for some reason — putting a bed on a deck or balcony, for instance — you'll need drainage holes to keep water from pooling.

Can I plant the same year I build it, or does the soil need to settle first?
You can plant the same season you build the bed. The fill settles somewhat during the first year as the bottom layer breaks down, but it doesn't meaningfully affect that first season's crops — just top up with extra soil or compost the following spring.

Is corten steel or stone a better choice than wood?
They last considerably longer than wood and need no maintenance at all, but cost more per meter and aren't something you can easily cut to custom sizes yourself. Corten steel also heats up in the sun, which can dry out soil faster near the walls compared with wood.

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