How to Build a Raised Garden Bed from Scratch

A raised garden bed is one of the most rewarding weekend projects you can build. Better drainage, better soil control, fewer weeds, and the satisfaction of growing your own food — all from a few cedar boards and a free Saturday.

This guide covers a classic 4×8 foot raised bed — the most popular size for good reason. It is large enough to grow a real variety of vegetables, small enough to reach every corner without stepping inside, and uses standard 8-foot lumber with minimal cuts.

Materials cost: $40–80. Professional build cost: $200–400. Weekend required: one.

Materials List

Why Cedar?

Cedar is the go-to material for raised garden beds because it is naturally rot-resistant without any chemical treatment — important when you are growing food. It weathers beautifully over time, gaining a silver-grey patina. A cedar raised bed lasts 10–20 years untreated.

Avoid pressure-treated wood for vegetable beds. Modern pressure-treated lumber uses copper-based preservatives that many gardeners prefer to keep out of their food-growing soil entirely. Cedar removes that concern completely.

Step 1: Choose Your Location

Before you cut a single board, site selection determines whether your garden succeeds or struggles.

• Sunlight: Vegetables need 6–8 hours of direct sunlight daily. Watch your yard for a full day before committing to a spot.
• Water access: Position within easy reach of a garden hose — you will be watering frequently.
• Level ground: A slightly sloped site is fine. Severely sloped ground requires terracing the bed, which adds complexity.
• Drainage: Avoid low spots where water pools after rain — raised beds solve most drainage issues but cannot fix a genuine bog.

Step 2: Cut Your Boards

For a standard 4×8 foot bed with 12-inch walls (two boards high), here is what you need cut:

• Long sides (4 boards): 8 feet each — no cuts needed from standard 8-foot boards
• Short ends (4 boards): Cut to 45 inches each (4 feet minus the thickness of two corner posts)
• Corner posts (4 pieces): Cut 4×4 lumber to 12-inch lengths — these anchor inside the corners

Step 3: Build the Frame

1. Stand two corner posts vertically on a flat surface, 45 inches apart
2. Align the first short end board flush with the outside face of both posts — drill two pilot holes and drive two 2.5″ screws per board-post connection
3. Attach the second short end board directly above the first in the same way — this completes one short wall (two boards high)
4. Repeat for the opposite short wall
5. Stand both short wall assemblies upright and connect them with the long side boards — drive screws through the board into the corner post face
6. Check for square by measuring diagonally corner to corner — both measurements should match within 1/4 inch
7. Add the second long side boards on each face to complete the 12-inch height

Step 4: Position and Prepare the Site

1. Set the completed frame in your chosen location
2. Use a level to check all four sides — shim with small stones or gravel under the low side if needed
3. Mark the perimeter with a shovel, then move the frame temporarily
4. Remove grass and weeds from inside the perimeter — dig down 2 inches and remove the turf
5. Lay cardboard or newspaper directly on the bare soil — this smothers remaining weeds without chemicals
6. Replace the frame over the prepared area
7. Staple landscape fabric inside the frame along the bottom edges

Step 5: Fill with Soil

This is where most first-time raised bed builders get surprised — a 4×8×12″ bed holds approximately 32 cubic feet of soil. That is a lot, and buying it in bags from the garden center is expensive. Order in bulk.

The ideal raised bed soil mix: 60% topsoil, 30% compost, 10% perlite or coarse sand for drainage. Many garden centers sell a pre-blended “raised bed mix” — convenient and well-balanced for most vegetables.

Frequently Asked Questions

What is the best size for a raised garden bed?

4×8 feet is the most popular size — large enough for meaningful growing, small enough to reach every spot from the outside without stepping in. For smaller spaces, a 4×4 bed is perfectly productive. Never make a bed wider than 4 feet or you will need to step inside to reach the center.

Do I need to seal or treat cedar raised garden beds?

No — cedar’s natural oils provide rot resistance without any treatment. Applying linseed oil can extend life slightly and enhance the color, but it is optional. Never use paint or chemical sealants on the inside of a food garden bed.

How deep should a raised garden bed be?

A minimum of 8 inches works for most vegetables. 12 inches is better — the standard for this build. Root vegetables like carrots and parsnips benefit from 18 inches. 12 inches covers 90% of what most home gardeners grow.

What can I grow in a 4×8 raised bed?

An enormous amount. A single 4×8 bed can support: 1 tomato plant, 1 pepper plant, 6 lettuce plants, 6 basil plants, 1 cucumber on a trellis, and a full row of green beans simultaneously. Succession plant for continuous harvest through the season.

How long will a cedar raised garden bed last?

With no treatment, a cedar raised bed lasts 10–20 years depending on climate. Wetter climates see the lower end, drier climates the higher end. The bottom boards that contact soil degrade first — they are the easiest to replace when the time comes.