Oliver Bexley
Why recycled timber and brick win the day
Raised beds earn their keep in small gardens. They lift the growing zone above tired, compacted ground, warm up faster in spring, and give you somewhere to perch with a mug of tea while you thin seedlings. Buying a new kit, though, can cost more than the vegetables you will harvest in the first three seasons. Reclaimed scaffold boards and a stack of salvaged bricks do the same job for a fraction of the price, and they look better with it — weathered, honest and entirely in keeping with a British garden.
There is a practical bonus too. Scaffold boards are usually around 38mm thick, so they hold their shape for years without bowing, even when they are holding back a tonne of wet soil.
Choosing boards and bricks safely
The one thing to be fussy about is what the timber has been treated with. Creosote was banned for sale to domestic users in the UK in 2003, but older boards still turn up at reclamation yards. It has a strong tarry smell and it should not be used for food growing. Modern scaffold boards are generally untreated spruce or pine, or treated with a copper or boron-based preservative that is fine in a garden — ask the seller which it is.
- Aim for boards around 225mm wide and 3.6m or 2.4m long. Long boards cut down neatly into two sides of a 2.4m bed.
- Reject anything with deep splits, rot along the lower edge or large knot holes. A few surface shakes are harmless.
- Reclaimed engineering bricks are ideal. Avoid crumbly, painted or heavily mortared bricks, and steer clear of anything salvaged from a site that handled chemicals or fuels.
- Knock old mortar off with a bolster chisel and club hammer. Wear gloves and eye protection — brick fragments are sharp.
Building the frame
Keep the bed no wider than 1.2m. That way you can reach the middle from either side without ever stepping on the soil, which is the whole point of the exercise. A bed 1.2m by 2.4m suits most plots, with a 600mm path around it — 900mm if you want to push a wheelbarrow comfortably.
For height, two boards stacked gives roughly 450mm, which is kind to backs and deep enough for carrots and parsnips. One board is plenty if you are simply improving thin soil over decent ground.
Set 100mm square posts at each corner, driven about 300mm into the ground, and screw the boards to them with exterior-grade screws of 60–75mm. Always drill pilot holes first; scaffold board is dense and splits easily. Three screws per board per corner is about right. If you would rather use bricks at the corners, build a pier two bricks square, either dry-laid and capped or set in mortar, and fix the boards to timber battens bedded into the pier.
A fully brick bed works well too. Lay the bricks dry in a staggered bond, two or three courses high, and sit the bottom course on a shallow trench of compacted hardcore. Dry-laid beds drain beautifully and can be dismantled if you move house.
Siting and lining
Pick the sunniest spot you have — six hours or more in summer for tomatoes, courgettes and beans. Level the ground first; a bed that rocks will pull itself apart. If the site is on concrete or paving, you will need to fill the base with a shallow layer of gravel and accept that drainage is slower.
Line the inside faces with a woven landscaping membrane. It stops soil trickling out through the gaps and keeps damp earth off the timber, which noticeably slows rot. Do not line the base — you want worms and drainage. A layer of plain cardboard over the ground before filling will smother weeds and rot down within a season.
Filling it without breaking the bank
A 1.2m by 2.4m bed at 450mm deep takes roughly 1.3 cubic metres of material, so filling it entirely with bagged compost is a costly mistake. Build it in layers instead:
- Bottom 100mm: logs, prunings, twiggy brash and woody garden waste. This rots slowly, holds moisture and saves a fortune in fill.
- Middle 150mm: half-rotted compost, spent grow-bag contents, grass clippings mixed with shredded paper.
- Top 200mm: the growing layer. Roughly 40% good topsoil, 40% well-rotted compost or manure, and 20% sharp sand or horticultural grit for drainage.
Water each layer as you go, then leave the bed to settle for a fortnight before planting. It will sink by 50mm or so — top it up with compost rather than more soil.
Planting up and keeping it going
Start with salads, radishes and dwarf French beans while the fill settles properly. Rotate crops between beds each year, and mulch with a 50mm layer of compost every autumn to feed the soil and keep weeds down.
Check the screws each spring and tighten any that have worked loose. If you want to protect the boards, brush the outside faces with linseed oil or a water-based wood preservative — never creosote, and never treat the inside faces. A sunken plastic bottle with pinprick holes by each thirsty plant gets water straight to the roots, which matters more than ever in a dry July.
Looked after this way, a bed built from other people's cast-offs will quietly outlast most of the shiny kits on the garden centre shelf.
