How to build a raised border: materials, height and planting

Why build a raised border?

A raised border is the Swiss army knife of garden design. It adds depth to a flat plot, saves your back when gardening, and gives you full control over soil quality. Waterlogged clay? Raised border. Free-draining sand? Raised border. I'm a fan, admittedly.

Tools like GardenWorld let you visualise how a raised border would look in your garden before you order materials. Getting the position and proportions right on screen saves costly mistakes in reality.

Comparing materials

Corten steel

The most popular choice right now. Corten starts shiny and develops that distinctive rust-brown patina within months. Available in 2 mm (decorative) to 3 mm (structural) sheets. Budget £35–70 per linear metre at 50 cm height. Garden suppliers and specialist online shops stock standard sizes.

Natural stone

Dry stone walls, flagstone stacks or slate give a cottage or Mediterranean feel. Expensive (£70–130/m²) but virtually indestructible. Perfect next to period properties.

Timber

Oak or larch sleepers are affordable (£18–35/m¹) but not forever. Even treated timber in ground contact lasts 10–15 years maximum. Always line the inside with a damp-proof membrane.

Brickwork

Brick-built raised beds are classic and long-lasting. The cost is in the labour-intensive bricklaying. Budget £90–180 per linear metre depending on height.

Getting the height right

Most people underestimate this. A 20 cm border is really just a raised edge — it doesn't feel like a proper feature. At 40–50 cm you get visual impact, easier gardening and enough soil volume for deep roots.

Go above 60 cm and you need stronger construction as soil pressure increases significantly. 3 mm corten handles this fine, but thinner materials may bow outward. Plan accordingly.

Drainage: don't skip it

The mistake I see most often in DIY raised borders: no drainage. Water needs somewhere to go, otherwise roots drown. Lay a 10 cm base of coarse gravel or lava rock. Add drainage holes in the sides for sealed constructions.

The ideal soil mix

Above the drainage layer, fill with:

• 50% good topsoil
• 30% compost
• 20% sharp sand

RHS partner gardens sell ready-made border mix, but mixing your own is cheaper and you know exactly what's in it.

Planting for raised borders

The elevated position means soil dries faster and gets colder in winter. Choose plants that cope:

• Grasses: Stipa tenuissima, Pennisetum
• Perennials: Salvia nemorosa, Echinacea, Nepeta
• Structural: Yew balls, Ilex crenata, clipped box (if box moth isn't an issue in your area)

Plant the edges so they spill slightly over the rim — trailing plants soften the hard line of the material.

Practical tips

Don't place your raised border flush against a fence. Leave at least 10 cm for air circulation, or the fence timber will rot. And remember that a filled border at 50 cm high and 1 metre wide weighs roughly 750 kg per linear metre. On a roof terrace or balcony, that's a non-starter.

Curious how a raised border would look in your garden? Upload your photo on GardenWorld and receive a custom design within a minute.