Build a raised bed in a weekend with basic tools and untreated wood

A raised plant bed is a wooden or composite box you fill with soil and plant into. You can build one yourself in four to six hours using a drill, a saw, and materials from a hardware store. The simplest design is a rectangle made from four boards screwed together at the corners, sitting directly on the ground. No foundation, no digging, no special skills required—just straight cuts and tight corners.

The most common size is 4 feet by 8 feet by 12 inches deep, which fits standard garden spaces and gives roots enough room for vegetables and perennials. You can make yours smaller or larger, but stay within those general proportions so the wood doesn't bow outward when the soil gets wet and heavy.

Key Takeaways

  • Use untreated cedar, composite boards, or galvanized steel—never pressure-treated wood, which contains chemicals that leach into soil.
  • A 4-by-8-foot bed 12 inches deep costs between $80 and $150 in materials and takes one person four to six hours to assemble.
  • Screw the corners together with 3-inch exterior-grade screws, using at least two screws per corner to prevent the wood from twisting.
  • Place the bed on level ground and add landscape fabric to the bottom to block weeds without preventing drainage.
  • Fill with a mix of topsoil and compost rather than garden soil alone, which compacts and drains poorly in a raised bed.

Choose your materials before you buy

Wood type matters because some treatments are toxic to food crops. Untreated cedar is the best choice—it resists rot naturally and lasts 10 to 15 years. Redwood works the same way. Both cost more upfront but don't leach chemicals. Composite boards (wood fiber mixed with plastic) last longer than wood and won't rot, but they cost two to three times as much and can warp in direct sun.

Never use pressure-treated wood, which contains copper compounds that accumulate in soil over time. Avoid railroad ties and old pallets unless you know their history. If cost is your main concern, untreated pine is cheaper than cedar and lasts five to eight years if you replace the bottom boards when they rot.

For a 4-by-8-foot bed 12 inches deep, you need two 8-foot boards and two 4-foot boards, all at least 2 inches thick. Buy them a little longer than you need—you'll trim them to exact length. You'll also need 16 exterior-grade screws (3 inches long), landscape fabric, and a level.

Cut the boards and assemble the frame

Lay the four boards on a flat surface and measure twice before cutting. A miter saw or circular saw works; a handsaw takes longer but works fine. Cut the two long boards to exactly 8 feet. Cut the two short boards to exactly 4 feet. Square up the ends so they sit flush against the long boards—a rough cut will leave gaps.

Stand the boards on edge to form a rectangle. Drill pilot holes (small starter holes) at each corner before screwing, which prevents the wood from splitting. Use a drill bit slightly smaller than your screw diameter. Drive two 3-inch screws through each short board into the end of each long board, angling them slightly inward so they pull the corners tight. Check that the corners are square by measuring diagonally from corner to corner—both measurements should be equal.

Flip the frame over and add two more screws to the underside of each corner for strength. The frame should feel rigid and not twist when you push on it.

Level the ground and position the bed

Choose a spot that gets at least six hours of direct sun for vegetables, or four hours for leafy greens. Clear away grass, weeds, and debris. You don't need to remove the sod entirely, but rake it down so the frame sits as level as possible.

Set the frame in place and use a level to check that it's even side to side and front to back. If one corner is higher, dig out soil from under that corner or add soil under the low corners. Spend time on this step—a bed that slopes will drain unevenly and water will pool in the low end. Once it's level, press down on the frame to settle it into the soil.

Line the bottom and fill with soil

Lay landscape fabric across the bottom of the bed, overlapping the edges by a few inches. This blocks weeds from growing up into your bed while still letting water drain through. Staple it to the inside of the frame so it doesn't shift when you add soil. You can skip this step if you're okay with weeds, but it saves work later.

Fill the bed with a mixture of topsoil and compost in roughly equal parts. Straight garden soil compacts too much in a raised bed and drains poorly. A 4-by-8-foot bed 12 inches deep holds about 32 cubic feet of soil—roughly 1.2 cubic yards. Buy it in bags or have it delivered in bulk. Spread it evenly and water it down so it settles. You'll likely need to add more soil a week later as it compacts.

Reinforce the sides if the bed is deeper than 12 inches

If you're building a bed taller than 12 inches, the weight of wet soil will bow the boards outward over time. Add internal bracing by screwing a 2-by-4 board vertically to the inside of each long side, centered between the corners. This prevents the boards from spreading apart.

For very tall beds (18 inches or more), add corner posts—4-by-4 boards at each corner, sunk 6 inches into the ground, with the frame screwed to them. This is overkill for a standard 12-inch bed but necessary if you're building something deeper.

Common mistakes to avoid

The most common error is using pressure-treated wood or untreated pine that's too thin. Thin boards bow outward quickly, and pressure-treated wood contaminates soil. Buy 2-inch boards minimum and untreated cedar if you can afford it.

The second mistake is skipping the level step. A sloped bed drains unevenly and makes watering harder. Spend 15 minutes getting it right. The third mistake is filling with garden soil alone instead of a soil-compost mix. Garden soil compacts and doesn't drain well in a raised bed—use the mix described above.

Finally, don't overtighten the screws. If you strip the wood or crack it, the frame will weaken. Screw until snug, then stop.

Frequently Asked Questions

Do I need a bottom to my raised bed?

No. A solid bottom blocks drainage and traps water. Landscape fabric alone is enough to stop weeds while letting water through. If you're in an area with burrowing pests like gophers, you can add hardware cloth (metal mesh) under the fabric, but most gardeners skip this step.

How deep should a raised bed be?

Twelve inches is standard and works for most vegetables and perennials. Shallow-rooted crops like lettuce and herbs need only 8 inches. Root vegetables like carrots and parsnips need 12 to 18 inches. If you're growing in clay soil, go deeper so roots aren't blocked by hard ground below.

Can I build a raised bed on a patio or deck?

Yes, but you'll need a solid bottom to contain the soil. Use plywood sealed with exterior stain, or buy a bed with a built-in bottom. Make sure water can drain somewhere—don't let it pool under the patio. Composite beds work better on hard surfaces because they won't rot if they stay wet.

How long does a wooden raised bed last?

Untreated cedar lasts 10 to 15 years. Untreated pine lasts 5 to 8 years. Composite boards last 20 years or more. The bottom boards rot first because they sit in wet soil. You can replace just the bottom boards instead of rebuilding the whole frame.

What size should I make my raised bed?

Four feet by eight feet is standard because it fits most garden spaces and you can reach the center from either side without stepping in. Smaller beds (2 by 4 feet) work in tight spaces. Avoid beds wider than 4 feet—you won't be able to reach the middle without stepping on the soil.