What to Specify Before Ordering Edging
Corten steel edging is supplied as straight strips, typically 1.5 m to 2.5 m long, with a folded top lip and either welded ground spikes or separate stakes. Weathering grades such as SPA-H to JIS G3125, Q355NH to GB/T 4171 or S355J2W to EN 10025-5 are the normal supply, in 1.5 mm, 2 mm or 3 mm thickness.
Spikes: integrated spikes of 100-150 mm make setting fast and keep the line true after frost movement. Separate 8-10 mm pins are an alternative on stony ground.
Height: a 100 mm strip buried to about 40 mm leaves roughly 60 mm exposed, which holds mulch and gravel without obstructing mowing.
Gauge: 2 mm holds a crisp line on straight runs; 3 mm resists point loading beside driveways and steps. Thin 1.5 mm strip is adequate only for decorative borders.
Jointing: a slide-together or overlap detail without separate clips produces a continuous line, and matching corner pieces avoid mitre gaps.
Standard fabrications are delivered in flat bundles with a mill certificate to EN 10204 type 3.1, a burr-free folded edge and a surface free of scale pockets that would later flake.
Tools and Ground Preparation
The work needs a half-moon edger or pointed spade, a tape measure, string line and stakes, a rubber mallet, a spirit level, a hacksaw or abrasive cutter, and gloves. Mark the line with string at the required offset, then cut a trench 100-120 mm deep with a flat base so the strip stands vertically. Remove roots and stones from the trench, and work when the soil is moist but not saturated, since a wet base will not hold a level line. On a slope, step the trench to follow the fall or set the strips to a constant exposed height.
Step-by-Step Installation
Cut the trench along the marked line and compact the base.
Place the first strip so the fold faces the planting bed and the spike points down.
Drive the strip with a rubber mallet or a block of timber, checking verticality and exposed height as you go.
Push the strip down until the top edge sits 50-60 mm above finished soil level.
Butt the next strip against the previous one and slide the joint together so the two sections overlap in line.
Backfill both sides with excavated soil, tamping in 50 mm layers, and firm the ground immediately behind the strip.
Check level and alignment along the full run before final compaction, and water the backfill to settle it.
Curves, corners and joints
Curves are formed by bending the strip progressively rather than at a single point. Short panels of 300-500 mm with a shallow relief cut on the inside of the bend allow a smooth radius without kinking, and an inside radius of at least 2-3 times the plate thickness avoids cracking. External corners are made with two cuts and a welded or folded return, and internal corners are formed by overlapping strips and pinning both ends.
Containing Gravel, Mulch and Corners
Where edging retains loose material, the back of the strip must be supported by compacted fill and, on soft ground, by a concrete collar of 100-150 mm width placed below the top of the strip. This stops the strip bowing outward under the weight of gravel. At gateways and path crossings, use a 3 mm section and pin the ends, since these are the points that receive foot traffic and mower wheels. A small drainage gap at the lowest point of a run prevents water trapped behind the edging from pushing soil over the top.
Stabilising the Patina and Aftercare
New edging begins to weather within weeks, and the surface reaches a stable, dark oxide within roughly 6 to 18 months of natural wet and dry cycling, depending on rainfall and airborne chloride. During that period rust-coloured water may run onto adjacent paving, which can be limited by pre-weathered supply or by a temporary protective strip. Before the patina stabilises the steel should not be painted; a clear matt sealer may be used later in coastal settings if runoff or salt load becomes a concern. Routine care consists of removing soil and debris from the exposed face with a soft brush, checking alignment after the first winter and re-tamping any section disturbed by frost.
Frequently Asked Questions
Q: How deep should Corten steel edging be buried?
A: A 100 mm strip is normally set with about 40 mm below finished soil level and 60 mm exposed. Deeper burial of 60-80 mm suits higher gauge edging on driveways, while decorative borders can be set shallower.
Q: Will the edging rust through and need replacing?
A: Not in normal service. The weathering grades form a protective oxide of about 50-100 micrometres, which limits further attack to a small fraction of the loss seen on plain carbon steel, and 2-3 mm sections last for decades in garden exposure.
Q: Can the edging be bent on site for curved borders?
A: Yes, using gradual bending or shallow relief cuts along the inside of the bend. Keep the inside radius at two to three times the plate thickness so the strip does not kink or crack at the fold.
Q: Do the strips need a concrete footing?
A: Only where loose material is retained or where traffic crosses the edge. In those locations a 100-150 mm concrete collar under the strip prevents bowing and keeps gravel behind the line.
Q: How soon does the rust colour appear?
A: A visible colour change starts within two to six weeks of exposure, and the surface settles into a stable, uniform patina after roughly 6 to 18 months of natural weathering. Supply can be pre-weathered when an even colour is needed at handover.
Q: Can edging be installed where lawn already exists?
A: Yes. Cut a narrow trench alongside the existing edge, lift the turf strip back, set the edging and re-lay the turf tight against it. Watering the reinstated strip settles the soil and closes the joint.
