Why Metal Edging Is Specified on Commercial Landscapes
Decorative metal edging has largely replaced timber and plastic on exposed sites because it holds a straight or shaped line indefinitely, resists mower contact and soil compression, and needs no annual maintenance. The weathering grades used for the purpose, including SPA-H to JIS G3125, Q355NH to GB/T 4171, S355J2W to EN 10025-5 and A606 Type 4 to ASTM A606, develop a dense oxide layer of roughly 50 to 100 micrometres within about 6 to 18 months of natural exposure. That oxide consumes the surface but limits further section loss to a small fraction of the rate measured on plain carbon steel, so 2-3 mm material gives a long service life in domestic and municipal landscaping.
Edging Types, Section and Fixing Options
| Type | Typical section | Fixing method | Best use |
|---|---|---|---|
| Spike-and-strip | 1.5-2 mm, 100 mm high, welded spikes | Drive spikes into compacted subgrade | Lawn and bed separation |
| Pinned heavy strip | 2-3 mm, 100-150 mm high | Separate 8-10 mm stainless pins at 500-600 mm centres | Driveways, mower edges, sloping ground |
| Concrete-backed | 3 mm, 150-200 mm high | Bedded in concrete haunch | Gravel retention, steps, planters |
| Bent profile | 2-3 mm folded section | Overlap folding or welded return | Pergolas, raised beds, seating surrounds |
Panels are normally supplied 1.5-2.5 m long with a folded top edge, burr-free cut ends and a mill certificate to EN 10204 type 3.1, with thickness tolerance referenced to EN 10029 or ASTM A6.
Excavation and Base Preparation
Set out the line with stakes and string at least one panel length ahead of the work. Excavate a trench 100 mm wide and 100-150 mm deep, with a flat compacted base. Where the edging retains gravel, extend the trench to about 200 mm and place a 100-150 mm concrete collar or a compacted granular bed, because unsupported edging bows under the lateral pressure of loose aggregate. The base of the trench must drain: a 20 mm fall towards a low point, or a small weep gap at the panel joint, prevents hydrostatic pressure from pushing the line out of alignment. On sloped ground, step the trench rather than following the fall continuously, so each panel keeps a constant exposed height and the top edge stays parallel to the surface.
Installation Sequence and Joint Alignment
Set and level the base, then mark the panel length along the string.
Position the first panel, check verticality with a spirit level and drive it down.
Fix with spikes or pins at 500-600 mm centres, keeping fasteners clear of the folded top edge.
Join the next panel with a sliding overlap so the two sections share one plane.
Check the top edge for line and level with a string line before backfilling.
Backfill in 50 mm compacted layers on both sides, watering each layer to settle it.
Recheck alignment after compaction and after the first heavy rain.
Tolerances and inspection points
A centre-line deviation of about 5 mm over a 2 m length and a top-edge level difference under 3 mm between adjacent panels are reasonable acceptance limits for landscape work. Inspection should also cover burrs on cut ends, uniformity of overlap, correct depth of burial and firmness of the backfill.
Corners, steps and interface details
External corners are formed by folding or welding a return; internal corners are formed by overlapping two strips and pinning both ends so neither can rotate. Where edging meets paving, the metal should finish 5-10 mm below the paving surface so that the mower and wheel loads pass over it without lifting the edge. At steps, a short return or a heavier 3 mm section prevents the edge being pushed off line by foot traffic. Joints between edging and planting must be sealed with compacted soil, not loose fill, or the first watering will wash material over the top.
Surface Condition and Aftercare
New material should be left unpainted so that wet and dry cycling can build the oxide layer; coatings applied too early block this process and trap moisture underneath. Handled carefully during installation, the folded top edge and the exposed face remain uniform, and colour variations between panels even out within the first year. Routine care means brushing off soil and cut grass, re-tamping any section disturbed by frost, and checking pin fixings after the first winter. On coastal sites, salt deposition lengthens the time needed for the oxide to stabilise, so a pre-weathered supply or a clear matt sealer over a matured surface is worth specifying at the outset.
Frequently Asked Questions
Q: Should Corten edging be painted after installation?
A: No. The surface needs wet and dry cycling to build its protective oxide, and paint interrupts that process while hiding the material's colour. Leave the edging bare and simply keep it clean.
Q: How far apart should fixing pins be placed?
A: Pins or spikes are normally set at 500-600 mm centres, with additional fixings at every joint, corner and slope change. Heavy 3 mm edging used for gravel retention should be fixed at 400 mm centres.
Q: How is edging kept straight along a gravel path?
A: Set a string line, use a concrete collar or compacted granular bed behind the panel, and backfill in thin compacted layers. A short weep gap at the lowest point relieves any water that collects behind the edging.
Q: Can metal edging be installed on a slope?
A: Yes. Step the trench so each panel is vertical and the exposed height stays constant, rather than bedding the edging along the fall of the slope. Stepping also reduces soil wash-out underneath the panels.
Q: What thickness is suitable for a driveway edge?
A: Use 2.5-3 mm material approximately 150 mm high, fixed with stainless pins and set below the paving surface. Thinner decorative sections deform when they take wheel loads and mower contact.
Q: Does the edging need maintenance once the patina has formed?
A: Only light care. Brush off soil and debris, re-firm any backfill loosened by frost, and check fixings after the first winter season; no repainting or surface treatment is required.
