Build a raised bed in a weekend with untreated wood, landscape fabric, and soil

A raised garden bed is a wooden or composite box you fill with soil and plant into. You can build one yourself in a day using basic tools and materials you can buy at any home center. The simplest version uses four boards screwed together at the corners, set on level ground, lined with fabric to keep weeds down, and filled with garden soil or a soil mix.

The whole project costs between $50 and $150 depending on size and materials. You do not need to be a carpenter—the cuts are straight, the angles are all 90 degrees, and the fasteners do the real work. Most people finish one bed in four to six hours, including digging out grass and filling with soil.

Key Takeaways

  • Untreated cedar, composite boards, or galvanized steel are the best materials; never use pressure-treated wood from before 2004 because the preservative contains arsenic.
  • A 4-by-8-foot bed 12 inches deep holds enough soil for most vegetables and fits standard garden tools.
  • Screw the corners together with 3-inch exterior-grade screws, two per corner, rather than nailing—screws hold better as the wood settles.
  • Landscape fabric stapled to the inside bottom stops grass and perennial weeds from growing up into your soil.
  • Level the ground first; a bed that sits crooked will have one end too shallow and one end too deep.

Choose your materials and size

Wood boards are the most common choice. Buy untreated cedar, which resists rot naturally, or composite boards made from wood fiber and plastic, which last longer but cost more. If you use regular pine or spruce, it will rot in three to five years—that is normal and acceptable if you are willing to replace it. Never use pressure-treated wood manufactured before 2004; the copper-based preservative in older stock contains arsenic. Modern pressure-treated wood (marked with a brown or green tint) is safe, though some gardeners avoid it anyway.

Standard dimensions are 4 feet by 8 feet by 12 inches deep. That size fits in most yards, uses boards you can carry alone, and holds enough soil for tomatoes, peppers, lettuce, and herbs. If your space is smaller, 4 by 4 feet works fine. If you want to grow root vegetables like carrots, go 18 inches deep instead of 12.

For a 4-by-8-foot bed, you will need two 8-foot boards and two 4-foot boards, all the same width (usually 10 or 12 inches). You will also need four 3-inch exterior-grade wood screws per corner (eight total), landscape fabric, a staple gun with staples, and soil.

Prepare the site and level the ground

Choose a spot that gets at least six hours of direct sun for vegetables. Mark out your bed with a tape measure or string. If grass is growing there, you can either remove the sod with a flat shovel or lay landscape fabric over it before you build—the fabric will kill the grass underneath, though it takes a few weeks.

Level the ground as much as you can. Use a long straight board and a level to check. If the ground slopes, dig out the high side and fill the low side until it is reasonably flat. A bed that sits on uneven ground will have shallow soil on one end and deep soil on the other, which wastes space and makes watering uneven.

Clear away any large rocks or roots. You do not need a perfectly flat surface—small bumps are fine—but avoid setting the bed on a slope steeper than a few inches over the length of the bed.

Assemble the frame with screws

Lay the four boards on the ground in a rectangle. Position them so the ends overlap at the corners—the short boards sit between the long boards, not on top of them. This makes the corners square and strong.

Drill a pilot hole (a small hole to guide the screw) at each corner, about 1 inch from the edge of the board. Use a drill bit slightly smaller than your screw diameter. Screw two 3-inch exterior-grade screws into each corner, one above the other, about 2 inches apart. Screws hold better than nails as the wood settles and shifts over time.

Check that the frame is square by measuring corner to corner diagonally. Both measurements should be the same length. If they are not, nudge the frame until they match. Tighten all screws once more before you move the frame into place.

Line the bottom with landscape fabric

Landscape fabric stops grass and perennial weeds from growing up into your bed. Lay the fabric across the bottom of the frame, overlapping the edges by a few inches. Staple it to the inside of the boards using a staple gun, spacing staples about 6 inches apart. Pull the fabric taut as you go so it does not sag.

You do not need to staple the corners perfectly—the soil weight will hold most of it down. The goal is to prevent grass from poking through the sides and the bottom. If you are worried about burrowing pests like voles or gophers, use hardware cloth (a metal mesh) instead of fabric, though it costs more and is harder to work with.

Fill with soil and let it settle

Fill the bed with garden soil, potting mix, or a blend of both. Garden soil is cheaper and heavier; potting mix drains faster and is easier to work with. Many gardeners use a mix: half garden soil, half potting mix or compost. Fill to about 1 inch below the rim so water does not spill over when you water.

The soil will settle over the first week or two, especially if you water it heavily. You may need to add more soil after a few days. This is normal. Do not pack the soil down—let it settle on its own.

If you are building in fall, you can fill the bed and let it sit over winter. The soil will compact and settle, and you will be ready to plant in spring. If you are building in spring, fill it and wait a few days before planting so the soil has time to settle.

Maintain the frame as it ages

Check the screws once a year, usually in spring, and tighten any that have loosened. Wood shrinks and swells with moisture and temperature changes, which can loosen fasteners.

If you used cedar or composite, the frame will last many years with no maintenance. If you used pine or spruce, the bottom boards will rot first, usually after three to five years. When that happens, you can replace just the bottom boards without rebuilding the whole bed—unscrew the corners, slide out the rotted boards, and screw in new ones.

Every few years, add compost or aged manure to the top of the bed to replace nutrients the plants have used. You do not need to replace all the soil.

Frequently Asked Questions

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

Yes. The concrete does not need to be level—the bed will sit on the high spots and rock slightly, which is fine. You may want to add a layer of cardboard under the frame to protect the concrete from moisture and to give roots a softer surface to grow into, though it is not required.

Do I need to put anything on the bottom besides landscape fabric?

Landscape fabric alone is enough for most situations. If you have a serious problem with burrowing pests like voles or gophers, use hardware cloth instead. If you are building on top of an old lawn, you can skip the fabric and let the grass decompose under the soil—it will add organic matter as it breaks down, though it takes longer.

How deep should the bed be for different plants?

Lettuce and herbs need 6 to 8 inches. Tomatoes, peppers, and beans need 10 to 12 inches. Carrots, beets, and other root crops need 12 to 18 inches. A 12-inch bed is a good compromise for a mixed vegetable garden.

What if the ground is not level?

Build the bed anyway. Level it as much as you can by digging and filling, but do not spend hours on it. A slight slope is fine. If the slope is steep, you can dig the frame into the ground on the high side and build it up on the low side to make it more level.

Can I use treated wood that says it is safe?

Modern pressure-treated wood (marked with a brown or green tint) is considered safe for vegetable gardens by most extension services. If you are uncomfortable with it, untreated cedar or composite boards are better choices, though they cost more.