Attaching a concrete edging strip to a garden path is a satisfying weekend DIY project that most homeowners can tackle confidently. The key is good preparation — a stable, well-compacted base and the right bedding mix will keep your edging upright and in place for years to come. No building consent is required for standard garden edging work, but always check with your local council if you're unsure about any earthworks or drainage implications on your property.
What You'll Need
Before you start, gather your materials and tools:
- Concrete edging strips (available in various lengths and profiles from Bunnings or Mitre 10)
- Dry-mix concrete or a bagged mortar/bedding mix (e.g., a sand-and-cement mix at roughly 4:1 ratio, or a pre-mixed product)
- Builders sand
- Pegs and string line
- Rubber mallet
- Spirit level
- Spade and hand trowel
- Tape measure
- Safety gloves and eye protection
Step 1 – Plan and Mark Out Your Line
Start by marking the line of your edging with pegs and a string line. This gives you a straight (or smoothly curved) guide to work to. For curved paths, use a garden hose laid on the ground to find a pleasing shape before you dig.
Measure the total length so you know how many edging strips to buy. Most concrete edging strips come in lengths of 600 mm to 1 m — factor in a small gap (around 5–10 mm) between each piece to allow for slight ground movement.
Step 2 – Excavate the Trench
Dig a trench along your marked line. The trench needs to be:
- Deep enough so the top of the edging strip sits at your desired finished height (usually flush with or just above the path surface)
- Wide enough to fit the edging strip plus a small amount of bedding mix on each side
As a rough guide, most standard edging strips are 50–75 mm wide and 150–200 mm tall, so your trench will typically be around 200–250 mm deep. Remove any loose soil, roots, or debris from the base.
Step 3 – Prepare the Bedding Base
Compact the base of the trench firmly with your foot or a hand tamper. Loose soil will cause edging to sink or lean over time.
Mix up a semi-dry bedding mix — a stiff sand-and-cement mortar (approximately 4 parts builders sand to 1 part cement) works well. It should hold its shape when squeezed in your hand but not be sloppy. Pre-mixed products from PlaceMakers or your local building supplier are a convenient option.
Spread a 50–75 mm layer of bedding mix along the base of the trench.
Step 4 – Set the Edging Strips
Press each concrete edging strip firmly into the bedding mix, tapping it down with a rubber mallet. Work along your string line, checking frequently with a spirit level to keep the top edge consistent.
Key tips:
- Keep a small expansion gap (5–10 mm) between strips
- Adjust the depth of bedding mix under each strip to maintain a level, even top edge
- For curves, you may need to angle adjacent strips slightly — concrete edging can crack if forced into too tight a radius, so choose a profile suited to curves if needed
Step 5 – Backfill and Haunch
Once the strips are set and level, haunch (support) them by packing more of your bedding mix firmly against both sides of the edging. This is the most important step for long-term stability — without good haunching, edging strips will lean or topple.
Use your trowel to press the mix tightly against the strip and slope it away from the edging at roughly 45 degrees on the garden side. On the path side, bring the mix up to just below the finished path surface.
Leave the haunching to cure for at least 24–48 hours before backfilling with soil on the garden side or laying any path surface material.
Step 6 – Finishing Up
Once cured, backfill the garden side with soil and firm it down. Clean any mortar smears off the face of the edging strips with a damp cloth before they fully harden.
For a neat finish, you can point the gaps between strips with a thin mortar mix, or leave them open to allow minor movement — both approaches are common in NZ conditions.
NZ Climate Considerations
New Zealand's varied climate — from wet, frost-prone winters in the South Island to humid summers in the North — means ground movement can be an issue. In areas with heavy clay soils or significant frost, allow slightly larger expansion gaps between strips and ensure drainage is adequate so water doesn't pool behind the edging. BRANZ has useful guidance on soil and drainage considerations for outdoor construction.
When to Call a Professional
Concrete edging is generally a safe DIY task, but consider hiring a qualified concreter if:
- You're edging a large area or a driveway where significant earthworks or drainage changes are involved
- The ground is very uneven, unstable, or on a slope
- You need edging integrated with a new concrete path or slab (formwork and poured concrete work is best left to an experienced concreter)
- You're unsure about any drainage implications near your home's foundation
You can find qualified local concreters on tradedirectory.co.nz to get the job done right.
Safety note: Always wear gloves and eye protection when working with cement-based products — wet cement is caustic and can cause skin irritation or burns with prolonged contact. Check WorkSafe NZ for general safe handling guidance.
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