How to Build a Raised Garden Bed (Complete Step-by-Step Guide)

Raised garden beds have exploded in popularity — and for good reason. You control the soil, drainage is built-in, weeds are dramatically reduced, and you can garden at any height. A well-built cedar raised bed will outlast a decade of growing seasons and can be made in a single afternoon for under $80 in materials.

This guide covers everything: choosing your design, picking the right wood, building it step by step, and filling it with the right soil mix for whatever you want to grow.

Choosing Your Size and Height

The most common mistake is building too wide. You should be able to reach the center from either side without stepping in, which limits useful width to about 4 feet. For length, 4x8 feet is the classic — it fits a standard sheet of plywood and is easy to plan around.

Height matters more than most people think. A 6-inch bed is fine for most vegetables but roots need more room. 10–12 inches gives you enough depth for almost any crop. A 30-inch tall bed (waist-high) is a game changer for anyone with back problems — no kneeling, ever.

The Best Wood for Raised Beds

• Cedar — the gold standard. Naturally rot-resistant, smells great, weathers to a beautiful silver-grey. No finish needed.

• Redwood — same benefits as cedar, harder to find in some regions.

• Douglas fir — less naturally rot-resistant but cheap and widely available. Seal the inside faces with linseed oil.

• Pressure-treated pine (modern CA-C or ACQ treatment) — considered safe for food gardens by the EPA since 2004, but avoid anything treated before 2004.

• Avoid: plain pine or spruce without treatment — they rot within 2–3 seasons in contact with soil.

What You Need

Tools

• Circular saw or miter saw

• Drill and driver

• Level

• Tape measure and square

• Rubber mallet (helpful for assembly)

• Safety glasses

Materials (for a 4x8x12" cedar bed)

• 3 boards: 2x12 cedar x 8ft (the long sides)

• 2 boards: 2x12 cedar x 4ft (the short ends)

• 4 corner posts: 4x4 cedar x 14" (anchor everything together)

• 2.5" exterior screws — stainless or coated

• Landscape fabric (optional — lines the bottom to block weeds)

Step-by-Step Build

1. Cut the corner posts to 14 inches — they sit inside the corners and give you 2 inches of post below the bed to anchor in soft ground.

2. Attach each long side board to two corner posts with 3 screws per joint. Pre-drill to avoid splitting.

3. Connect the short end boards to complete the rectangle. Check that all corners are square by measuring the diagonals — they should match.

4. If you're going on grass, flip the frame upside down and staple landscape fabric across the bottom before flipping it back.

5. Set the bed in its location. Check it's level — shim with gravel if needed. Pound the posts into soft ground with a rubber mallet for stability.

6. Fill with soil mix (see below) to about 1 inch below the top rail.

The Right Soil Mix

Do not fill a raised bed with topsoil from the yard — it compacts badly and may carry weeds and disease. The best mix for most vegetables:

• 1/3 compost — the engine of the bed, feeds plants all season

• 1/3 peat moss or coco coir — holds moisture without compacting

• 1/3 coarse perlite or vermiculite — keeps drainage and airflow

This blend (often called "Mel's Mix" after the Square Foot Gardening method) drains well, never crusts over, and produces heavy harvests. A 4x8x12" bed holds about 32 cubic feet — buy soil in bulk bags or have a landscape yard deliver a cubic yard if building multiple beds.

Tips to Make It Last

• Line the inside bottom with landscape fabric but leave the sides bare — cedar doesn't need it and fabric on the sides slows root penetration.

• Add a simple drip irrigation line at ground level — a few dollars of hardware and you'll water less all season.

• Top-dress with 1–2 inches of compost every spring instead of digging and tilling.

• Build two or three beds at once — the second one takes half the time.

Get the Full Plan

Our Raised Planter Box PDF plan includes a complete materials and cut list, the full step-by-step build, tips for the waist-high version with legs (no bending ever), and finishing recommendations for the wood. Available as an instant digital download at scottswoodcraftsllc.com.