A raised bed made of Corten steel combines two things that rarely come together in the garden: a look that becomes more beautiful with every year, and a construction that lasts for decades without maintenance. In this guide we explain what really matters in planning, choosing the dimensions, sheet thickness, filling and planting – with the practical knowledge from our own production and the most frequent questions from our customers.
Why Corten steel is the ideal material for raised beds
Corten steel (material no. 1.8965 / 1.8946) is a weather-resistant structural steel with copper and chromium content. Unlike ordinary structural steel, under weathering it forms a firmly adhering rust patina that permanently protects the material underneath from rusting through. The result: no coating, no paint, no maintenance – and a warm, natural surface that blends harmoniously into any garden.
- Long-lasting: decades of service life without rusting through, because the patina acts as a protective layer.
- Food-safe: The patina consists of natural rust compounds and does not release any harmful substances – vegetables and herbs can be grown without concern.
- Sustainable: 100 % recyclable, no film, paint or chemical layers.
- Dimensionally stable: steel does not warp, does not swell and does not rot – unlike wood.
It is important to distinguish it from simple "structural steel with a rust look": untreated S235/St37 continues to rust porously until it has rusted through. Why this is a technical and not a visual difference is explained in our article Corten steel vs. structural steel St37: the difference that determines rust.
Planning: location and the right dimensions
The location
For vegetables the rule is: as sunny as possible, ideally with the long side facing south. Plan for access from at least two sides so that you can work comfortably. A raised bed without a base stands ideally on lawn or garden soil – rainwater drains away, earthworms and soil life migrate in from below. It works just as well on a terrace or balcony, as long as excess water can drain off.
The right dimensions
The most important rule: the middle of the bed has to remain within reach. These guide values have proven themselves:
- Width: 60–100 cm if the bed is accessible from both sides; against a wall, better no more than 70 cm.
- Working height: 80–90 cm for back-friendly gardening while standing; 40–60 cm for a terrace, balcony or as a low bed edging.
- Length: as much as the space allows – from a length of about 150 cm, growing fruiting vegetables such as tomatoes and zucchini really pays off.
With a made-to-measure product you do not have to stick to standard sizes: we manufacture our made-to-measure Corten steel raised bed to the exact centimeter – length 40–240 cm, width 40–200 cm, height 40–120 cm. For your dimensions, the configurator shows you a sketch, the empty weight and the fill quantity per layer. We also produce special shapes such as L-shaped beds on request.
Customer photo: a large made-to-measure raised bed shortly after installation – the patina is already starting to develop at the edges.
Sheet thickness and structural design: what really matters
Soil is heavy. A cubic meter of moist substrate quickly weighs more than a ton, and this soil pressure acts on the side walls permanently. Two design features determine whether a raised bed still has straight walls after years:
1. The right sheet thickness for the length
The longer the side wall, the larger the area on which the soil pressure acts. That is why, with our raised beds, the length determines the minimum thickness: up to 70 cm in length 2 mm, up to 140 cm 3 mm, up to 190 cm 4 mm, above that 5 mm. You can select a thicker sheet in the configurator at any time. For comparison: many raised bed kits from the DIY store use 1–1.5 mm throughout – regardless of the size.
2. Welded instead of bolted
A body welded at all four corners distributes the soil pressure across one connected system. Bolted and slot-together connections, by contrast, are weakest at exactly the corners – where the forces are greatest. In addition, our construction has a double-folded top edge turned inwards, which stiffens the upper rim and forms a pleasant, safe resting edge, a folded bottom edge for a secure stand, and a horizontal stiffening profile on the inside that supports the side walls against bulging.
The top edge grows with the sheet thickness – the thicker the sheet, the wider and higher the fold: 2 mm gets at least 30 × 20 mm, 3 mm then 40 × 25 mm, 4 mm 45 × 35 mm and 5 mm 60 × 40 mm (width × height). A wider resting surface of up to 100 mm can be set in the configurator. This is not cosmetics but statics: a larger folded profile has a higher section modulus and therefore supports the longer, more heavily loaded wall correspondingly better.
Filling the raised bed: the right layer structure
The classic structure from coarse to fine provides drainage, nutrients and an active soil life:
- Drainage layer (bottom, 20–30 cm): coarse tree and shrub cuttings, branches, wood chips. Provides ventilation and water drainage.
- Green layer (15–20 cm): upturned turf sods, leaves, green cuttings, straw.
- Compost layer (15–20 cm): semi-mature to mature compost as a nutrient reserve.
- Planting layer (top, 15–20 cm): high-quality garden or raised bed soil.
The lower layers decompose over the years, releasing nutrients and warmth and slowly settling – simply top up with compost and soil every spring. On a terrace or balcony, a drainage layer of expanded clay or gravel is enough for low beds, with a separating fleece and planting soil on top. The configurator calculates how many liters you need per layer for your dimensions.
Planting: what grows when in a Corten steel raised bed?
A freshly layered raised bed is particularly rich in nutrients in the first year – ideal for heavy feeders such as tomatoes, zucchini, pumpkin, cabbage and celery. In the second year come the moderate feeders (lettuces, carrots, onions, peppers), and from the third year light feeders such as herbs, radishes and peas also do well.
- For hot summers: heat-loving species such as tomatoes, peppers, eggplants, rosemary, thyme and sage benefit from the warm microclimate of the metal bed.
- Still sowable in midsummer: summer radishes, leaf lettuce, arugula, spinach and corn salad deliver fresh harvests into the fall.
- Use mixed cultivation: basil between tomatoes, onions next to carrots – good neighbors help prevent pests.
Watering in summer: how to keep the raised bed from drying out
Raised beds warm up faster than ground-level beds – that extends the season, but increases the water requirement in midsummer. Three measures keep the moisture in the bed:
- Water in the morning instead of in the midday heat – the water reaches the roots before it evaporates.
- Mulching: a layer of grass clippings or straw reduces evaporation by up to half.
- Drip irrigation: a drip hose under the mulch layer supplies the bed evenly – even while you are on vacation.
A dimpled membrane or polystyrene panel on the inside also acts as a buffer: it insulates the soil in winter and in summer keeps the heat of the south side away from the roots.
Combining Corten steel in the garden
The warm rust patina harmonizes with almost all materials of modern garden design: ornamental grasses such as fountain grass and Chinese silver grass set soft contrasts against the clean steel edge, light gravel and chipping surfaces make the patina glow, wooden decks and exposed concrete underline the modern line. As a low bed edging, as a privacy screen or in combination with further raised beds, this creates a consistent overall design.
Patina and care: what you should know
- Condition on delivery: steel-gray or partly rusted. The patina develops purely through weathering.
- Duration: after about 1.5 to 3 years the rust patina is fully formed.
- Rust water: in the early stage, run-off rainwater can leave marks. On sensitive surfaces a mat or a gravel strip helps at first; on lawn, gravel and dark stone slabs nothing is needed.
- Winter: Corten steel is completely frost-proof. The bed stays outside, the soil life keeps working – in spring simply top it up and replant.
- Maintenance effort: none. No painting, no oiling, no sanding.
Speeding up the patina: here is how
If you do not want to wait 1.5 to 3 years for the full rust patina look, you can deliberately kick-start the patina: with a rust accelerator such as the RustIT+ rust activator, the warm rust layer develops in a few days instead of years – and the protective effect of the patina is fully retained.
- Prepare: The steel surface must be dry and free of grease and dust. Wipe off fingerprints with a little methylated spirit, cover sensitive floors and adjacent surfaces.
- Apply: Spray the rust activator evenly onto all visible surfaces. Wear gloves and safety goggles.
- Let it work: First rust forms after a few hours; for an even, rich patina, repeat the application after 24 hours. Rain and sun then deepen the color tone by themselves.
Packaging and shipping: how your raised bed arrives
A welded raised bed travels as a single, finished component – and is prepared for freight shipping with corresponding care: the bed is fixed to a sturdy wooden pallet with lashing straps, completely wrapped in cardboard and stretch film and secured with warning tape against additional loading. That way it reaches you without transport damage – free of scratches and dimensionally stable.
Fully welded and steel-gray ex works: the bed is fixed to the pallet with straps – the rust patina develops later in your garden.
Ready for shipping: protected all round with cardboard, stretch film and warning tape on the pallet.
The freight forwarder delivers the pallet to you – allow for two to four people when setting up large beds. The bed is always carried while empty and only filled at its final location.
Frequent questions answered briefly
Is Corten steel safe for vegetables?
Yes. The patina consists of natural iron oxides and does not release any harmful substances into the soil.
How heavy is a Corten steel raised bed?
Depending on the dimensions and sheet thickness, between around 13 kg (40 × 40 × 40 cm) and 336 kg (240 × 120 × 110 cm). Delivery is by freight forwarder on a pallet; the bed is always carried while empty.
Does the raised bed need a base?
No – the open contact with the ground is intentional: water drains away, soil organisms migrate in. On terraces, a drainage layer takes care of the water run-off. If you would still like a base, you get it firmly welded in and with drainage holes – it keeps voles and foreign roots out.
Do I have to assemble the bed?
Not with a welded raised bed: it comes as one finished component – unpack, align, fill.
Conclusion: planned properly once, enjoyed for decades
A Corten steel raised bed is a purchase for life: maintenance-free, dimensionally stable and with a look that gains character with every year. What matters is choosing the right dimensions for your location, a sheet thickness that suits the size and a clean layer structure when filling. Sun, rain – and your plants – take care of everything else.
Would you like your raised bed in your preferred size? Our Corten steel raised bed made to measure is welded all round, manufactured in Germany and delivered with no assembly required – you choose length, width and height to the exact centimeter, and the necessary minimum sheet thickness is included in the price.
