What you need to build a raised bed

A raised garden bed is a wooden or composite box you fill with soil and plant into. The most common size is 4 feet long, 2 feet wide, and 12 inches deep, though you can build any dimensions that fit your space. You will need four boards (usually cedar or composite lumber), corner brackets or screws, a drill or screwdriver, a level, landscape fabric, and soil to fill it.

Cedar is the standard choice because it resists rot for 10 to 15 years without treatment. Composite boards last longer but cost more. Avoid pressure-treated lumber from before 2004, as it contains arsenic. Newer pressure-treated wood is safe but will not last as long as cedar in wet soil.

The tools required are basic: a power drill or hand screwdriver, a level, a tape measure, and a saw if you are cutting boards to length. Many hardware stores will cut boards to your specifications for free or a small fee, which saves time and ensures square corners.

Key Takeaways

  • Cedar boards resist rot longer than pressure-treated wood and are the most popular choice for raised beds that will last a decade or more.
  • A 4-by-2-foot bed 12 inches deep is the standard size and holds enough soil for most vegetables without being too wide to reach the center.
  • Corner brackets or 3-inch screws hold the frame together; brackets are easier for beginners and allow you to disassemble the bed later.
  • Landscape fabric on the bottom stops weeds from growing up into your bed but allows water to drain through.
  • Filling a standard bed requires about 8 cubic feet of soil, which costs between $30 and $60 depending on soil quality and your location.

Choosing your location and preparing the ground

Place your raised bed where it will receive at least six hours of direct sunlight per day. Most vegetables need this much light to produce well. If your yard is shaded, choose a spot that gets morning sun, as that dries dew and reduces disease.

Clear the ground of grass and weeds where the bed will sit. You do not need to remove soil, but you should pull out any large roots or rocks. If the ground is very uneven, you can level it by removing high spots and filling low ones, or straightforward place the bed and accept a slight tilt — a level bed looks better but is not necessary for the plants to grow.

Measure out your bed footprint with a tape measure or string. Mark the corners with stakes or chalk so you know exactly where to position the boards.

Assembling the frame

Lay the four boards on the ground in a rectangle, with the ends of two boards meeting the long sides of the other two. This creates a square or rectangular frame. Before fastening anything, check that the corners are roughly square by measuring diagonally from corner to corner — both diagonals should be the same length.

Attach the corners using either corner brackets or 3-inch deck screws. Corner brackets are L-shaped metal pieces that bolt or screw to the inside of two boards at each corner. They are easier to install and allow you to take the bed apart later if you move. Screws go through one board into the end grain of the other; use at least two screws per corner, spaced a few inches apart.

If you use screws, drill a pilot hole first (a small hole that guides the screw and prevents the wood from splitting). Tighten the screws firmly but do not over-tighten, as this can strip the wood or bend the boards. Once all four corners are fastened, place the frame in its final location and use a level to check that the top edges are even. Adjust by adding or removing soil underneath.

Installing landscape fabric and filling with soil

Cut a piece of landscape fabric to fit the bottom of the bed, with a few inches of overlap at the edges. Landscape fabric stops perennial weeds and grass from growing up through your soil while still allowing water to drain. Staple or pin the fabric to the inside of the boards, or straightforward lay it flat on the ground — it will stay in place once you add soil.

If you are building on top of an existing garden bed or very rich soil, you can skip the fabric. If you are building on lawn or in a spot with persistent weeds, the fabric is worth the effort.

Fill the bed with soil to within an inch of the top. Use a mix of topsoil and compost; a common ratio is three parts topsoil to one part compost. This blend drains well and holds nutrients. Avoid filling with only compost, as it compacts and drains poorly over time. Avoid only topsoil, as it lacks the organic matter plants need.

Spread the soil evenly and water it lightly to help it settle. After a few days, the soil will compact slightly, and you may need to add more to bring it back to the top edge.

Building a bed on hard ground or concrete

If you are building on concrete, asphalt, or very hard-packed soil, you have two options. The first is to drill holes through the landscape fabric and into the ground below, then add a weed barrier that is thicker and more durable than standard landscape fabric. This allows roots to penetrate slightly into the soil beneath, which helps with drainage and gives plants access to deeper nutrients.

The second option is to skip the ground contact entirely and use a solid bottom — either plywood or a thick rubber mat. This turns the bed into a container and means you must fill it completely with purchased soil, which costs more. However, it gives you complete control over soil quality and eliminates any risk of contamination from the ground below. This method works well if you are building on contaminated soil or if you want to grow in a space where no soil exists.

Sizing your bed for your space and needs

The standard 4-by-2-foot size is popular because it is wide enough to hold multiple rows of plants but narrow enough that you can reach the center from either side without stepping into the bed. If you have limited space, a 3-by-3-foot bed works well. If you have room and want to grow more, a 4-by-4-foot bed is manageable, though reaching the center becomes harder.

Depth matters for different plants. Lettuce and herbs need only 6 inches of soil. Root vegetables like carrots and beets need 12 inches. Tomatoes and peppers do well with 12 inches but prefer 18 inches if you can provide it. A standard 12-inch depth is a good compromise for a mixed vegetable garden.

If you are building multiple beds, space them at least 2 feet apart so you can walk between them and access both sides. Closer spacing saves space but makes maintenance harder.

Maintaining your raised bed frame

Cedar beds typically last 10 to 15 years before the wood begins to rot, usually starting at the bottom corners where moisture collects. You can extend the life by keeping the soil level below the top edge of the boards, which reduces water splash and rot. Avoid letting water pool against the outside of the frame.

Composite boards last 20 years or longer but cost two to three times as much as cedar. They do not rot, splinter, or need sealing, making them lower-maintenance. Some composite boards are made from recycled plastic and wood, which appeals to gardeners who want to avoid new lumber.

When a cedar bed finally rots, you can replace individual boards without rebuilding the entire frame. Remove the corner brackets or screws, slide out the damaged board, and slide in a new one. This repair takes about 30 minutes and costs far less than building a new bed.

Frequently Asked Questions

Do I need to put anything on the bottom of a raised bed to stop gophers or moles?

If gophers or moles are a problem in your area, line the bottom with hardware cloth (a metal mesh with half-inch holes). Staple it to the inside of the boards before adding soil. This stops burrowing animals from entering from below while still allowing water to drain. If you do not have a gopher problem, this step is unnecessary.

Can I build a raised bed on top of grass without removing it first?

Yes. The grass will die under the bed as it is deprived of light, and it will decompose into the soil over time, adding organic matter. Lay landscape fabric on top of the grass before adding soil to speed up decomposition and stop any grass from growing up through the sides. Without fabric, grass may creep in from the edges.

What is the best soil to fill a raised bed with?

A mix of topsoil and compost works best — roughly three parts topsoil to one part compost. This drains well, holds nutrients, and supports most vegetables. Avoid pure compost, which compacts and drains poorly. Avoid pure topsoil, which lacks organic matter. Many garden centers sell pre-mixed raised bed soil that is ready to use.

How much does it cost to build a standard raised bed?

A 4-by-2-foot cedar bed costs $40 to $80 for boards, $10 to $20 for fasteners, and $30 to $60 for soil, totaling roughly $80 to $160. Composite boards cost two to three times more. Prices vary by region and wood quality. Buying boards from a local sawmill is often cheaper than a big-box store.

Can I build a raised bed without using wood?

Yes. Composite boards, galvanized metal, or even stacked stone work as frames. Metal lasts the longest but conducts heat and can make soil too warm in summer. Stone looks attractive but is heavy and difficult to level. Wood remains the most affordable and easiest option for most gardeners.