Start with the frame and fill

A raised bed is a wooden or composite box you fill with soil and plant into. The simplest version uses four boards screwed or nailed at the corners, set on level ground, then filled with a soil mix. You do not need a foundation or special tools — a drill, a saw, and a level are enough to build one that will last several seasons.

The most common size is 4 feet by 8 feet by 12 inches deep, which fits standard lumber and gives you enough room to grow vegetables without reaching into the middle. Smaller beds (3 by 6 feet) are easier to manage if you have limited space or physical reach. Depth matters: 12 inches works for lettuce and herbs, but tomatoes and root vegetables need 18 inches or more.

Key Takeaways

  • Build the frame from untreated wood, composite boards, or galvanized metal, assembled at the corners with screws or nails on level ground.
  • Fill the bed with a mix of topsoil, compost, and peat moss or coconut coir in roughly equal parts, not garden soil alone.
  • Position your bed where it gets at least six hours of direct sun for vegetables, and check that water drains away rather than pooling.
  • You can plant when ready after filling, but the soil will settle over the first few weeks and you may need to add more.

Choose your materials and size

Untreated wood boards are the cheapest option and will last five to ten years depending on climate. Cedar and redwood last longer but cost more. Avoid pressure-treated wood from before 2004, which contains arsenic; newer pressure-treated lumber is safer but still not ideal for vegetables. Composite boards (wood fiber mixed with plastic) cost more upfront but last 15 to 20 years and do not rot.

Galvanized metal raised beds are durable and take up less visual space, though they heat up faster in sun and cool faster in cold. Corrugated metal beds are lighter and cheaper than solid metal. Avoid aluminum in acidic soil, as it can leach into plants.

Standard lumber comes in 2-by-6, 2-by-8, 2-by-10, and 2-by-12 sizes. A 2-by-6 board is actually 5.5 inches tall, so two stacked make 11 inches deep — close enough to 12 inches. For a 4-by-8 bed, you need four 8-foot boards and four 4-foot boards, plus eight corner brackets or 16 screws.

Assemble the frame on level ground

Choose a spot that is relatively flat. If the ground slopes, dig out the high side and fill the low side until the footprint is level — use a 2-foot or 4-foot level to check. Uneven beds will have water pooling on one side and drying out on the other.

Lay the boards in a rectangle and check that the corners are square by measuring diagonally from corner to corner; both diagonals should be equal. Screw the corners together with 3-inch exterior wood screws (two or three per corner) or nail them with 3-inch galvanized nails. Screws hold better and are easier to remove later if you need to disassemble the bed.

If you are stacking boards for extra depth, screw them to each other at the corners as well. Do not use interior drywall screws or regular nails — they will rust or snap in wet soil.

Fill with the right soil mix

Do not use garden soil from your yard or bags labeled "garden soil" — they compact and drain poorly in a raised bed. Instead, mix three ingredients in roughly equal parts: topsoil, compost, and peat moss or coconut coir. This creates a light, fluffy texture that holds moisture without waterlogging.

A 4-by-8-by-12-inch bed holds about 32 cubic feet of soil. You can buy this in bags (expensive and heavy) or by the cubic yard from a landscape supplier (cheaper and delivered). One cubic yard fills about 27 cubic feet, so order 1.5 cubic yards to have enough. Ask the supplier to deliver a mix or to blend it for you if they can.

Fill the bed to the top, then water it thoroughly. The soil will settle over the next week or two, dropping 1 to 3 inches depending on the mix. Add more soil after settling so the bed is full again before you plant.

Position for sun and drainage

Most vegetables need six to eight hours of direct sun per day. Lettuce and leafy greens tolerate four to six hours. Herbs vary — basil wants full sun, but mint and parsley grow in partial shade. Observe your yard through the day before you place the bed, or use a sun calculator app with your address to see which areas get full sun.

Water must drain away from the bed, not pool around it. If your yard is naturally wet or clay-heavy, you can place the bed on a slight slope or dig a shallow trench around it to channel water away. Raised beds on grass will eventually kill the grass underneath, which is fine — the grass will decompose and add organic matter to the soil below.

Plant when ready or wait for settling

You can plant into a new bed the same day you fill it, but understand that the soil will compact and settle. Transplants (seedlings you buy or start indoors) handle settling better than direct-seeded crops. If you direct-seed lettuce or carrots, the soil may shift and expose the seeds.

Many gardeners fill the bed a week or two before planting, water it, let it settle, then top it off before planting. This takes more time but gives you a more stable planting surface. If you plant when ready, water gently and check the bed after a few days — you may need to add soil around plants that have sunk.

Maintain the bed year to year

Each season, add 1 to 2 inches of compost to the top of the bed before planting. This replaces organic matter that breaks down and keeps the soil light and fertile. After three to five years, the original soil will have decomposed significantly and you may need to empty the bed and refill it, or straightforward add several inches of fresh soil on top.

In winter, you can leave the bed empty, plant a cover crop like clover to add nitrogen, or fill it with leaves for composting in place. Perennial herbs like thyme and oregano can stay in the bed year-round in most climates.

Frequently Asked Questions

Do I need a bottom or barrier in my raised bed?

No barrier is required. A solid bottom prevents drainage and root penetration into the soil below. If you are concerned about pests or contaminated soil, you can lay landscape fabric on the ground before filling — this stops burrowing rodents but still allows water and roots to move through. Many gardeners skip this step entirely.

Can I use old wood pallets to build a raised bed?

Pallets work if they are untreated or stamped "HT" (heat-treated). Avoid pallets marked "MB" (methyl bromide), which is a pesticide. Pallets are often shorter than standard boards, so you may need to stack them or supplement with additional boards to reach 12 inches deep.

How much does it cost to build a raised bed?

A 4-by-8-foot bed with untreated wood costs roughly $40 to $80 for materials, plus $30 to $60 for soil if you buy it in bags, or $40 to $80 if you order by the cubic yard. Composite or cedar beds cost $150 to $300 for the frame alone. Soil is usually the bigger expense than the frame.

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

Yes, but drainage becomes critical. Water cannot drain through concrete, so it will pool inside the bed. Use a bed with drainage holes or drill holes in the bottom before placing it. You will also need to water more often because the soil dries faster without moisture moving into the ground below.

What if my raised bed is in shade part of the year?

Grow shade-tolerant crops: lettuce, spinach, kale, arugula, parsley, mint, and chives all produce in four to six hours of sun. Tomatoes, peppers, and basil need full sun and will be weak or unproductive in shade. You can also move the bed if it is small, or wait until trees lose their leaves in fall to get more sun.