Raised garden beds are one of the best things you can do for your garden. They warm up faster in spring, drain better than in-ground beds, keep weeds manageable, and let you control your soil quality completely. Once you build your first one, you'll want more.
This guide covers everything — the right dimensions, materials, soil mix, and how to lay out your plants for maximum yield from a small space.
The Golden Dimensions
Getting the size right matters more than most beginners realise. Here's why each measurement counts:
Width — Never wider than 4 feet
The most important rule: keep your bed no wider than 4 feet (48 inches). This lets you reach the center from either side without stepping in and compacting the soil. If your bed is against a wall or fence, keep it 2 feet wide. Comfortable reach = healthier soil = better plants.
Length — 8 feet is the sweet spot
An 8-foot length maximises a standard 8-foot lumber board with no waste. You can go longer — 12 feet works great — but longer beds need a center support to prevent the sides from bowing outward over time as soil pressure builds.
Height — Taller is better
Standard raised beds are 6–12 inches tall. For most vegetables, 10–12 inches is ideal — deep enough for root vegetables like carrots and beets. If you have back or knee issues, go 24–30 inches tall for a waist-height bed — it's a game changer for comfort.
Best Materials for Raised Beds
🌲 Wood Options
- Cedar — Best choice. Naturally rot-resistant, lasts 10–20 years, smells great
- Redwood — Similar to cedar, excellent longevity, premium price
- Douglas Fir — Budget-friendly, lasts 5–7 years untreated
- Pine (treated) — Use only ACQ or CA treated lumber — safe for food gardens
- Avoid — Old railway ties, CCA-treated wood (contains arsenic)
Building the Bed
Choose your location
Most vegetables need at least 6 hours of direct sun per day — 8 hours is even better. Observe your yard through the day before committing to a spot. Avoid placing beds under trees (root competition, shade, and falling debris). Ensure you're within reach of a garden hose. Level ground is ideal but not essential — a slight slope is fine.
Cut and assemble the frame
For a standard 4×8 bed using 2×10 or 2×12 lumber: cut two 8-foot long pieces and two 3-foot 9-inch short pieces (to account for the thickness of the long boards). At each corner, drive 3-inch exterior screws through the long side into the end of the short piece — 3 screws per corner. For taller beds, stack two layers of boards and offset the joints like brickwork for strength. Check the frame is square before placing.
Prepare the ground beneath
Place cardboard or several layers of newspaper on the ground inside the bed frame before adding soil. This smothers existing grass and weeds without chemicals. It breaks down within a season, adding organic matter to your soil. If you have gophers or moles in your area, staple a layer of hardware cloth to the bottom of the frame before placing it — this keeps burrowing pests out completely.
Fill with the perfect soil mix
This is the most important investment in your raised bed. Never use plain garden soil — it compacts badly and drains poorly in a raised bed. The best mix is the classic "Mel's Mix": one third compost, one third vermiculite, one third peat moss or coir. For a 4×8×12" bed you'll need about 32 cubic feet of mix. This sounds like a lot but it's the single biggest factor in how well your plants grow.
💡 Save Money on Soil: Buy compost in bulk from a local landscape supplier — it's far cheaper per cubic foot than bagged compost from a garden centre. Many municipalities also offer free compost. Mix it yourself and save up to 60% compared to pre-mixed raised bed soil.
Plan your planting layout — square foot method
The square foot gardening method is perfect for raised beds. Divide your bed into a 1-foot grid using string or wooden dividers. Each square gets a different plant, with the number of plants per square depending on plant size. Tall plants (tomatoes, corn) go on the north side so they don't shade shorter plants. This method gets 4–10× more yield from the same space compared to traditional row gardening.
Planting Density Guide
🌿 Plants Per Square Foot
- 🥕 Carrots — 16 per sq ft
- 🥬 Lettuce — 4 per sq ft
- 🌿 Herbs (basil, parsley) — 4 per sq ft
- 🥦 Broccoli — 1 per sq ft
- 🍅 Tomatoes — 1 per sq ft (need support)
- 🫑 Peppers — 1 per sq ft
- 🥒 Cucumbers — 2 per sq ft (vertical)
- 🧅 Onions — 9 per sq ft
- 🫘 Bush beans — 9 per sq ft
- 🌽 Corn — 1 per sq ft (plant in blocks)
Add irrigation and mulch
Raised beds dry out faster than in-ground gardens — consistent watering is key. A simple drip irrigation system on a timer takes all the guesswork out of watering and can be set up for under $30. After planting, cover all bare soil with 2–3 inches of straw or wood chip mulch. This retains moisture, regulates soil temperature, and dramatically reduces weeding. It's one of the simplest improvements you can make.