Why Reclaimed Timber Deserves a Place in Your Garden

A raised bed is one of the most useful things you can build in a small British garden. It lifts your growing area above heavy clay, gives you control over the soil, warms up faster in spring, and saves your back from endless bending. It also looks tidy, which matters when your plot is overlooked by next door's kitchen window.

Buying new timber for the job can be surprisingly expensive, and much of what's sold for raised beds has been pressure-treated with chemicals you may not want leaching into soil you're growing carrots in. Reclaimed timber sidesteps both problems. Old scaffolding boards, floorboards, decking joists and pallet collars are widely available, often free, and untreated timber is perfectly safe for edible crops. It will rot eventually, but a well-built bed lined with cardboard should give you six to ten productive years before anything needs replacing.

Choosing and Checking Your Boards

Not all reclaimed wood is suitable. Have a good look at anything you're offered before you commit.

• Avoid anything treated or coated. Old railway sleepers oozing tar, creosoted fence panels, and timber with a green or brown chemical tint are all best left alone for growing food.
• Look for sound, straight boards. Scaffolding boards are ideal at roughly 22cm wide and 3.5cm thick. Decking boards work well too, though you'll need two or three stacked to reach a decent depth.
• Reject rot and infestation. Soft, crumbly patches, live woodworm holes, or boards that snap when you flex them belong on the bonfire, not in your vegetable patch.
• Check for nails and screws. Run a magnet or a stiff brush along each board. A hidden nail will ruin a saw blade and can catch your hand badly.

Give everything a scrub with a stiff brush and let it dry. If the boards are filthy, a quick wash with warm soapy water is enough. There's no need to sand them smooth.

Working Out Size for a Small Space

The golden rule for a raised bed you'll actually use is this: you should be able to reach the middle from either side without stepping on the soil. That means a maximum width of about 1.2 metres. Length is flexible — 1.2m or 2.4m suits most small gardens — and a depth of 20 to 25cm is plenty for salads, beans, onions, chard and most herbs. Root crops like parsnips and maincrop carrots want closer to 30cm.

Before you cut anything, lay the boards out on the ground where the bed will sit. Check the space from every angle, including how it affects your path to the back door. Once it's filled with soil, moving it is a genuinely miserable job.

For a standard 1.2m square bed you'll need four boards of that length, plus four corner posts cut from 5cm x 5cm timber at roughly 40cm long — long enough to sit 10cm into the ground and still hold the full height of the boards.

Building the Frame

Mark out your rectangle with string and canes, then clear the ground of perennial weeds, especially couch grass and bindweed. There's no need to dig it over; the cardboard layer will deal with most of what's left.

Stand the corner posts at each corner, driving them into the ground with a mallet so they're firm and upright. It's worth checking with a spirit level at this stage — a bed that's noticeably out of true will bother you every time you look at it.

Fix the boards to the posts using 75mm galvanised screws, two per board end. Drill pilot holes first; reclaimed timber splits easily, particularly along old nail lines. If your boards are thinner than 3cm, pre-drill every hole without exception.

For a bed longer than 2.4m, add a central post on each long side to stop the boards bowing outwards once the weight of wet soil presses against them. Push the assembled frame down until the boards sit level with the ground, then firm the soil back around the posts.

Lining with Cardboard and Filling

Now for the layer that does the quiet, unglamorous work. Lay plain brown cardboard over the whole base of the bed, overlapping the sheets by at least 15cm. Remove any plastic tape and staples first. Damp it thoroughly with a watering can so it moulds to the ground.

Cardboard suppresses existing weeds, holds moisture, and slowly breaks down to feed the soil life beneath. It also slows the rot at the base of your timber. Avoid glossy printed card and anything waxy.

For filling, a roughly even mix works well:

• Two parts topsoil — bought in bags or borrowed from a healthy part of your own garden.
• One part well-rotted compost or manure, at least a year old.
• A handful of blood, fish and bone scattered through the top 10cm before planting.

Fill to within 3cm of the top, then water it well and let the whole thing settle for a week or two before sowing. It will drop by a few centimetres, and you can top it up with a little more compost.

Plant it up, mulch with a thin layer of grass clippings or leaf mould, and keep it watered through dry spells. Your reclaimed boards will silver with age, the cardboard will vanish into the soil, and by midsummer you'll have a bed that's earning its keep — built for almost nothing, and better for your plot than anything you could have bought flat-packed.