The basic steps to build a raised bed

A raised garden bed is a wooden or composite box you fill with soil and plant into. Building one takes a weekend and requires only a saw, a drill, and fasteners. The simplest approach is to buy untreated cedar or composite boards, cut them to length, drill pilot holes, and screw the corners together—then set it on level ground, add landscape fabric to the bottom, and fill it with soil.

You do not need special tools or construction experience. The frame itself is just four boards joined at the corners. Once it is assembled and sitting in place, the hard part is done. Everything after that is filling and planting.

Key Takeaways

  • Untreated cedar and composite boards are the most durable choices; pressure-treated wood is cheaper but contains chemicals that can leach into soil over time.
  • A standard raised bed is 4 feet long, 2 feet wide, and 12 inches deep, which balances ease of reach with enough soil volume for most vegetables.
  • Screwing the corners together is faster and stronger than nailing, and you can disassemble the bed later if you need to move it.
  • Landscape fabric on the bottom stops weeds and lets water drain; you do not need to dig out the ground underneath.
  • The total cost for materials ranges widely depending on board type and size, but a basic 4-by-2-foot bed typically runs between $50 and $150 in lumber alone.

Choosing boards and materials

Untreated cedar is the standard choice because it resists rot naturally and lasts 10 to 15 years without treatment. It costs more than pine or fir but does not require sealing or replacement as often. Cedar is also safe for vegetables and herbs from day one.

Composite boards (usually wood fiber mixed with plastic) last 20+ years and never rot, but they cost significantly more upfront. They are heavier to handle and can warp in extreme heat, but they require no maintenance.

Pressure-treated wood is the cheapest option and lasts longer than untreated softwood, but modern pressure-treated lumber contains copper compounds that can leach into soil. Many gardeners avoid it for vegetable beds, though it is acceptable for ornamental plantings. If you use it, line the interior with landscape fabric or plastic to reduce contact.

Avoid railroad ties and old pallets. Railroad ties contain creosote, a toxic preservative. Pallets may have been treated with pesticides or used to transport hazardous materials.

Sizing and cutting your frame

A standard raised bed is 4 feet long, 2 feet wide, and 12 inches deep. This size is deep enough for most vegetables (carrots, lettuce, tomatoes), wide enough that you can reach the center from either side, and long enough to be useful without being unwieldy. You can build larger or smaller, but this is the most practical starting point.

To build a 4-by-2-foot bed, you need two boards 4 feet long and two boards 2 feet long. If you are buying boards at a lumber yard, ask them to cut them to length—most will do this for free or a small fee. If you are cutting at home, use a circular saw or hand saw and wear safety glasses.

For depth, 12 inches is standard. If you are growing shallow-rooted plants like lettuce or herbs, 8 inches works. If you want to grow root vegetables or deep-rooted perennials, go 18 inches. Taller beds are easier on your back but require more soil and cost more.

Assembling the frame

Lay the four boards on a flat surface in a rectangle. At each corner, drill two pilot holes (small holes that guide the screw and prevent splitting) through the end of one board and into the side of the adjacent board. Use a drill bit slightly smaller than your screw diameter.

Drive 3-inch exterior-grade wood screws through the pilot holes. Use at least two screws per corner—four total per corner is better and makes the frame much more rigid. Exterior-grade screws resist rust and hold better than standard drywall screws.

Check that the frame is square by measuring diagonally from corner to corner. Both diagonal measurements should be the same length. If they are not, adjust the frame until they match, then tighten all screws fully.

If you want to add a bottom to the frame (to keep burrowing pests out), cut a piece of hardware cloth or sturdy wire mesh to fit inside and staple it to the underside of the boards before you place the bed in the garden.

Positioning and preparing the site

Choose a spot that gets at least 6 hours of direct sun for vegetables. Level the ground as much as you can—a slightly uneven site is fine, but a very tilted one will cause water to pool on one side. You do not need to remove grass or dig out the soil; the weight of the bed and the soil inside will kill the grass over time.

Lay landscape fabric over the ground inside the footprint of the bed. This stops weeds from growing up into your soil and lets water drain through. Overlap the seams by a few inches and find the corners with landscape staples or rocks so it does not shift when you add soil.

If you are concerned about burrowing pests (moles, voles, gophers), staple hardware cloth to the bottom of the frame before placing it, or lay hardware cloth on the ground and set the frame on top of it.

Filling and settling the soil

A 4-by-2-foot bed that is 12 inches deep holds about 8 cubic feet of soil. Most garden centers sell soil by the cubic yard (27 cubic feet), so you will need about one-third of a cubic yard. You can also buy bags of potting mix or garden soil, though this is more expensive per volume.

Fill the bed to within an inch of the top. The soil will settle over the first few weeks, so you may need to add more later. Water the bed thoroughly after filling to help it settle and to give plants a moist environment to start in.

If you are planting when ready, use a high-quality garden soil or potting mix blend. If you are building in fall and planting in spring, you can fill with compost, aged manure, or a mix of soil and compost—these will break down and settle over the winter, creating rich planting medium.

Maintenance and longevity

Cedar beds need no treatment if you are comfortable with them weathering to gray. If you want to preserve the color, explore a cedar stain or sealer every 2 to 3 years. Never paint the interior—paint can chip into the soil.

Check the corners and edges each spring for rot or damage. If a board begins to split or rot, you can unscrew it and replace just that board without rebuilding the whole frame. This is one advantage of screwing instead of nailing.

Add 1 to 2 inches of compost to the top of the bed each year. This replenishes nutrients and keeps the soil level consistent as it settles.

Frequently Asked Questions

Do I need to line the bottom with plastic or cardboard?

Landscape fabric is enough. It stops weeds and lets water drain. Plastic or cardboard blocks drainage and can trap water, which causes rot and root problems. Use landscape fabric only.

Can I build a raised bed on top of concrete or pavement?

Yes, but water will not drain away. You will need to drill drainage holes in the bottom of the frame or add a layer of gravel inside before the soil to prevent waterlogging. Alternatively, use a bed with a removable bottom so you can lift it and let water escape.

How deep does a raised bed need to be for tomatoes?

Tomatoes need at least 12 inches, ideally 18 inches. Deeper soil holds more water and nutrients, which tomatoes demand. If your bed is only 8 to 10 inches deep, tomatoes will struggle and dry out quickly.

What is the best wood to use if I want the bed to last 20 years?

Composite boards last the longest (20+ years) but cost the most. Untreated cedar lasts 10 to 15 years and costs less. If budget is tight, cedar is the best value for a long-lasting bed.

Can I stack two raised beds on top of each other to make it deeper?

Yes. Screw or bolt them together at the corners so they do not shift. This is a good way to deepen a bed without rebuilding it, though stacked beds can be unstable if the bottom bed settles unevenly.