Why Raised Beds Are Worth Building

Raised garden beds have become a staple of productive gardens for good reason. They drain better than ground-level beds, warm up earlier in spring, keep weeds at bay, and make it far easier to grow vegetables, herbs, and flowers without back-breaking ground preparation. A well-built wooden raised bed can last a decade or more with minimal upkeep.

Choosing the Right Wood

The wood you choose will determine how long your bed lasts. It will be in constant contact with soil and moisture, so rot resistance is essential.

  • Cedar: The gold standard for raised beds. Naturally rot-resistant due to its oils, lightweight, and looks beautiful. More expensive but worth it.
  • Douglas Fir: A more affordable option with decent rot resistance when kept off the ground.
  • Larch: European larch is highly durable and a great value option in the UK.
  • Oak: Extremely durable and attractive, though heavy and pricier.
  • Avoid: Pressure-treated wood with older CCA (chromated copper arsenate) treatments in vegetable beds. Modern ACQ-treated timber is generally considered safer, but cedar or larch remain the safest choices for edibles.

Materials for a Standard 120cm × 90cm Bed

  • 4 × planks: 120cm × 20cm × 3.8cm (long sides)
  • 4 × planks: 90cm × 20cm × 3.8cm (short sides)
  • 4 × corner posts: 40cm × 5cm × 5cm
  • Exterior-grade screws (stainless steel or galvanised, 6cm)
  • Weed membrane (optional but recommended)
  • Quality compost and topsoil mix to fill

Step-by-Step Build Instructions

  1. Prepare your site. Choose a level spot with good sunlight (at least 6 hours daily for vegetables). Clear grass and weeds from the area.
  2. Cut your lumber. If your timber supplier hasn't cut to length, use a circular saw or hand saw to cut all planks and corner posts to the dimensions above.
  3. Assemble the frame. Stand two long planks and two short planks on edge to form a rectangle. Position a corner post inside each corner, flush with the top edge of the planks. Screw through the planks into the posts — two screws per join per plank layer.
  4. Stack for height. For a two-board height (ideal for most veg), repeat with a second layer of planks, offsetting the joins from the layer below for added strength.
  5. Position in the garden. Move the assembled frame to its final position. Check it's level using a spirit level — adjust by digging out or adding soil underneath as needed.
  6. Lay weed membrane. Cut a sheet of weed membrane to size and lay it inside the base of the bed. This suppresses weeds without blocking drainage.
  7. Fill with growing medium. Fill the bed with a 60/40 mix of quality topsoil and compost. For deep beds, you can fill the bottom third with wood chip, straw, or cardboard to save on compost costs (a technique called hugelkultur).

Finishing and Maintenance

If you want to extend the life of non-cedar timbers, apply an exterior wood oil or beeswax-based preservative to the outer faces. Avoid painting the inside of the bed. Each year, top up the growing medium with a 5–8cm layer of fresh compost as the soil level naturally drops.

Tips for Success

  • Orient longer sides east–west to maximise sun exposure across the bed
  • Keep width to 120cm maximum so you can reach the centre from either side
  • Add a simple drip irrigation line if your climate is dry — raised beds dry out faster than in-ground plots
  • Consider adding a cold frame lid in early spring to get a head start on the growing season

A raised bed built this weekend can be planted the same day. Few DIY projects deliver such immediate, tangible results — and come harvest time, you'll be doubly glad you built it.