How to Build Raised Garden Beds

The standard: 4 feet wide, 8 feet long, 12 inches deep. Cedar or fir. Filled with topsoil + compost. That's it.

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Sizing

Width: 4 feet max — you need to reach the center from either side. 2-3 feet for beds against a fence or wall.

Length: 8 feet is standard (matches common lumber). Add a center support for anything longer.

Height:

• 6" — minimum, works on good existing soil
• 12" — the sweet spot for most vegetables including root crops
• 18-24" — for poor/rocky soil or to reduce bending

A 4x8x12" bed needs ~32 cubic feet (~1.2 cubic yards) of soil.

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Materials

Good choices

Material	Lifespan	Notes
Cedar	10-15 years	Naturally rot-resistant. Pricier.
Douglas fir	5-8 years	Budget option. Works fine.
Galvanized steel	20+ years	No rot. Can heat up in direct sun.

Avoid

• Railroad ties — contain creosote, toxic for food gardens
• Pallets — often chemically treated, full of hidden nails

Modern pressure-treated lumber (ACQ, not the old arsenic CCA) is considered safe — but many food gardeners prefer untreated wood.

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How to Build (4x8, 12" deep)

Materials:

• 4x 2x12 boards, 8 ft (sides)
• 4x 2x12 boards, 4 ft (ends) — or cut two 8-footers in half
• 4x 4x4 posts, 12" (corners)
• 3" exterior deck screws
• A drill

Steps:

1. Stand boards on edge. Screw sides into ends (3 screws per joint, pre-drill to prevent splitting).
2. Place a 4x4 post in each inside corner, screw through sides into post for rigidity.
3. Level the site — clear grass/weeds. No need to dig.
4. Set the bed in position. Optional: staple hardware cloth (1/2" mesh) to the bottom if gophers are an issue.
5. Fill with soil mix.

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The Soil Mix

Don't use plain garden soil — it compacts.

Classic mix:

• 1/3 topsoil
• 1/3 compost
• 1/3 coarse vermiculite or perlite

Budget version: 50/50 bulk topsoil and compost works fine.

Buy in bulk from a landscape supply — much cheaper than bags. One 4x8x12" bed needs ~1 cubic yard.

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Placement Checklist

• 6-8 hours of direct sun — most important factor
• Near a water source — you'll water often
• Level ground
• 2-3 feet between beds for walking paths
• North-south orientation maximizes sun exposure (helpful, not critical)

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Common Mistakes

1. Too wide — can't reach center → you step in it → compacted soil
2. Too shallow — tomatoes and root crops need 12"+
3. Cheap soil — defeats the purpose of raised beds
4. Solid bottom — beds must drain into the ground below
5. Built in shade — check sun throughout the day before building

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Cost

Item	Cost
Cedar lumber (one 4x8 bed)	$80-120
Douglas fir	~$40-60
Bulk soil (1 cubic yard)	$50-80
Total per bed	$90-200