Start with the right location and materials

A raised garden bed works best in a spot that gets at least six hours of direct sunlight each day—more if you're growing vegetables. Before you build, check that the ground is relatively level and clear of large rocks or debris. You'll need four boards (usually 2-by-10 or 2-by-12 lumber), four corner brackets or L-brackets, a drill or screwdriver, soil, and optionally a landscape fabric to line the bottom.

Cedar and composite materials last longer than pine, but pine is cheaper and works fine for three to five years. Avoid pressure-treated wood from before 2004, as it contains arsenic. Measure your space first—a 4-by-8-foot bed is standard and straightforward to reach across, but 3-by-6 feet works in tight spaces.

Key Takeaways

  • Choose a location with at least six hours of direct sun and level ground, then measure your space before buying materials.
  • Assemble the frame on the ground using corner brackets, then position it in place and check that all corners are square.
  • Line the bottom with landscape fabric to block weeds, then fill with a mix of topsoil and compost rather than garden soil alone.
  • Water the soil thoroughly after filling so it settles, then wait a few days before planting to let everything compact.
  • Raised beds drain faster than ground beds, so you may need to water more often during hot weather.

Assemble the frame using corner brackets

Lay all four boards flat on the ground in the shape of a rectangle. Position an L-bracket or corner bracket at each corner on the inside of the frame, then drill pilot holes and screw the brackets into both boards at each corner. Use at least two screws per bracket—one into each board. Make sure the screws are tight enough that the boards don't shift when you lift the frame.

Once all four corners are bracketed, flip the frame over and check that all four corners form right angles. You can do this by measuring diagonally from corner to corner—both diagonals should be the same length. If they're not equal, the frame is out of square; loosen the brackets slightly and adjust until the diagonals match.

Position the bed and prepare the ground

Carry or drag the assembled frame to your chosen location. If the ground underneath is uneven, you can dig out high spots or add soil to low spots, but don't spend hours leveling—a slight slope is fine. The frame itself will settle unevenly over time, and that's normal.

If you're building on grass or weeds, you have two options: remove the sod first (labor-intensive but thorough), or lay down cardboard or several layers of newspaper inside the frame before adding soil. The cardboard will break down over one to two seasons and block most weeds. Overlap the cardboard pieces by at least six inches so weeds can't push through the seams.

Line the bottom and add landscape fabric

Landscape fabric is optional but worth using—it blocks weeds from growing up through the bottom while still allowing water to drain. Lay it across the bottom of the frame, overlapping the edges by several inches and stapling it to the inside of the boards. You don't need to staple every inch; every foot or so is enough to keep it in place while you fill.

If you skip the fabric, you'll spend more time pulling weeds later, especially if the ground underneath has perennial weeds like dandelions or bindweed. The fabric doesn't stop all weeds—seeds that land on top of the soil will still sprout—but it stops the ones pushing up from below.

Fill with soil and compost, then water

Don't use garden soil alone—it compacts too much in a raised bed and drains poorly. Instead, mix topsoil and compost in roughly equal parts, or use a ratio of three parts topsoil to one part compost if compost is expensive in your area. Fill the bed to about two inches below the top of the boards, leaving room for mulch and so water doesn't spill over the edge when you water.

Water the soil thoroughly after filling—use a hose or watering can and soak it until water runs out the bottom. The soil will settle over the next few days as air pockets collapse. You may need to add more soil after a week to bring it back to the right level. Wait at least three to five days after filling before planting, especially if you're using fresh compost, which can heat up as it breaks down.

Mulch the surface and plan for drainage

Add two to three inches of mulch—wood chips, straw, or shredded leaves—across the top of the soil. Mulch keeps the soil cooler, reduces water loss, and suppresses weeds. Keep the mulch a few inches away from plant stems so it doesn't trap moisture against the stems and cause rot.

Raised beds drain much faster than ground-level beds, which is good for preventing root rot but means you'll water more often, especially in summer. Check the soil by pushing your finger two inches down; if it's dry, water. In hot weather, you may need to water every day or every other day. Consider adding a soaker hose or drip line if you have a large bed or live in a dry climate.

Frequently Asked Questions

How deep should a raised bed be?

Most vegetables need 8 to 12 inches of soil depth. Shallow-rooted crops like lettuce and spinach can grow in 6 inches, but root vegetables like carrots and beets need at least 12 inches. A 10-inch-deep bed (using 2-by-10 boards) is a good middle ground that works for most home gardens.

Can I build a raised bed directly on concrete or asphalt?

Yes, but you'll need to drill drainage holes in the bottom or line it with landscape fabric with small cuts for water to escape. Without drainage, water pools underneath and roots rot. Concrete also gets very hot in summer and can warm the soil too much, so consider placing the bed in partial shade if possible.

What's the best time of year to build a raised bed?

Spring and fall are ideal because the soil is moist and easier to work with, and you can plant right away. You can build in summer or winter, but summer heat makes the work harder and winter soil is often frozen or waterlogged. If you build in late fall, wait until spring to plant most crops.

Do I need to replace the soil every year?

No. Add two to three inches of compost or aged manure to the top each spring to replenish nutrients. After three to five years, you may want to replace the top few inches if it's become very compacted or depleted. A well-maintained bed can produce for many years with just annual compost additions.

How do I keep pests and animals out of my raised bed?

For insects, row covers or netting over the plants work well. For larger animals like rabbits or deer, install a fence around the bed at least two feet tall, or use a cage-style cover. For burrowing animals like moles or voles, line the bottom with hardware cloth (metal mesh) before adding soil, though this adds cost and labor.