A raised bed made of Corten steel combines two things that rarely come together in the garden: a look that becomes more beautiful every year, and a construction that lasts for decades without any maintenance. In this guide we explain what really matters when it comes to planning, choosing dimensions, sheet thickness, filling and planting – with the practical knowledge from our own production and the questions our customers ask most often.
Why Corten steel is the ideal material for raised beds
Corten steel (material no. 1.8965 / 1.8946) is a weather-resistant structural steel alloyed with copper and chromium. Unlike ordinary structural steel, under weathering it forms a firmly adhering noble 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.
- Safe for food crops: The patina consists of natural rust compounds and releases no 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, swell or rot – unlike wood.
It is important to distinguish it from plain „structural steel with a rust look“: untreated S235/St37 keeps rusting porously until it has rusted right 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 decides about 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. On lawn or garden soil, a raised bed without a base is ideal – rainwater drains away, and 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 must remain within reach. These guide values have proven themselves:
- Width: 60–100 cm if the bed is accessible from both sides; against a wall, a maximum of 70 cm is better.
- Working height: 80–90 cm for back-friendly gardening while standing; 40–60 cm for a terrace, a balcony or as a low bed edging.
- Length: as much as the space allows – from around 150 cm in length, growing fruiting vegetables such as tomatoes and zucchini really pays off.
With a made-to-measure product you do not have to settle for standard sizes: our Corten steel raised bed made to measure is available in over 1,200 combinations – length 40–240 cm, width 40–120 cm, height 40–110 cm, each in 10 cm increments. We also produce special shapes such as L-shaped beds or intermediate dimensions on request.
Customer photo: a large made-to-measure raised bed shortly after installation – the patina is already starting to develop along the edges.
Sheet thickness and structural design: what really matters
Soil is heavy. One cubic meter of moist substrate quickly weighs more than a ton, and this soil pressure acts permanently on the side walls. 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 we automatically size the material thickness of our raised beds according to the length: 40–70 cm are made in 2 mm, 80–140 cm in 3 mm, 150–190 cm in 4 mm and 200–240 cm in 5 mm. For comparison: many kit raised beds from the hardware 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 plug-in connections, by contrast, are weakest exactly at the corners – precisely where the forces are greatest. In addition, our design features 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 braces 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 30 × 20 mm, 3 mm then 40 × 25 mm, 4 mm 45 × 35 mm and 5 mm 60 × 40 mm (width × height). This is not cosmetic but structural: a larger folded profile has a higher section modulus and therefore braces the longer, more heavily loaded wall correspondingly better.
Filling the raised bed: the right layer structure
The classic build-up from coarse to fine ensures drainage, nutrients and active soil life:
- Drainage layer (bottom, 20–30 cm): coarse tree and shrub cuttings, branches, wood chippings. Provides aeration and water drainage.
- Green layer (15–20 cm): upturned turf sods, leaves, green waste, straw.
- Compost layer (15–20 cm): semi-mature to mature compost as a nutrient reservoir.
- Planting layer (top, 15–20 cm): high-quality garden or raised bed soil.
The lower layers decompose over the years, releasing nutrients and warmth while slowly settling – simply top up with compost and soil each spring. On a terrace or balcony, a drainage layer of expanded clay or gravel is sufficient for low beds, with a separating fleece and potting soil on top.
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, squash, cabbage and celery. In the second year come the medium feeders (lettuces, carrots, onions, peppers), and from the third year light feeders such as herbs, radishes and peas also thrive.
- 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 worth sowing in midsummer: summer radishes, cut-and-come-again lettuce, arugula, spinach and lamb’s lettuce deliver fresh harvests into the fall.
- Use mixed cultivation: basil between tomatoes, onions next to carrots – good companions help prevent pests.
Watering in summer: how to keep the raised bed from drying out
Raised beds warm up faster than ground-level beds – this extends the season but increases the water demand 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.
An internal dimpled membrane or polystyrene panel also acts as a buffer: it insulates the soil in winter and in summer keeps the heat of the south-facing side away from the roots.
Combining Corten steel in the garden
The warm rust patina harmonizes with almost every material used in modern garden design: ornamental grasses such as fountain grass and Chinese silver grass provide soft contrasts to the crisp steel edge, light gravel and chipping surfaces make the patina glow, and wooden decking and exposed concrete underline the modern line. Used 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
- Delivery condition: steel-gray or partly rusted. The patina develops solely through weathering.
- Duration: after about 1.5 to 3 years the noble rust layer is fully formed.
- Rust water: in the early phase, running rainwater can leave marks. On sensitive surfaces a mat or a strip of gravel helps at first; on lawn, gravel and dark stone slabs nothing is needed.
- Winter: Corten steel is completely frost-proof. The bed stays outside and the soil life keeps working – in spring simply top it up and plant it anew.
- Maintenance effort: none. No painting, no oiling, no sanding.
Speeding up the patina: how it works
If you do not want to wait 1.5 to 3 years for the full noble rust look, you can deliberately kick-start the patina: with a rust accelerator such as the RustIT+ rust activator, the warm rust layer develops within 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 and cover sensitive floors and adjacent surfaces.
- Apply: Spray the rust activator evenly onto all visible surfaces. Wear gloves and safety goggles.
- Let it work: The 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 on their own.
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 secured with lashing straps to a sturdy wooden pallet, fully wrapped in cardboard and stretch film, and marked with warning tape against additional loading. That way it reaches you without transport damage – scratch-free and dimensionally stable.
Fully welded and steel-gray ex works: the bed is secured to the pallet with straps – the noble 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 two to four people for setting up large beds. The bed is always carried empty and only filled at its final location.
Frequently asked questions, briefly answered
Is Corten steel safe for vegetables?
Yes. The patina consists of natural iron oxides and releases no 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, and the bed is always carried empty.
Does the raised bed need a base?
No – the open contact with the ground is intentional: water drains away and soil organisms move in. On terraces, a drainage layer ensures water runoff.
Do I have to assemble the bed?
Not with a welded raised bed: it arrives 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 every year. What matters is choosing the right dimensions for your location, a sheet thickness that matches 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 desired size? Our Corten steel raised bed made to measure is welded all round, made in Germany and delivered ready to install – you choose length, width and height in 10 cm increments, and the matching sheet thickness is included.
