Yes, laying concrete edging around your garden beds is absolutely something most NZ homeowners can tackle themselves. It doesn't require a building consent (it's well within Schedule 1 exemptions — though always confirm with your local council if you're unsure), and with a bit of preparation and patience, you can achieve a clean, long-lasting result that keeps lawn and garden neatly separated.
What You'll Need
Before you start, gather your tools and materials:
- Spade and edging spade – for cutting a clean trench
- String line and pegs – to keep your edging straight or evenly curved
- Timber formwork (e.g. 25 × 100 mm pine boards) – to hold the wet concrete in shape
- Concrete – either bagged pre-mix or site-batched (see mix guide below)
- Float and trowel – for finishing the surface
- Spirit level – to keep the top edge consistent
- Wheelbarrow and mixing trough or electric mixer
- Safety gear – gloves, safety glasses, and waterproof boots (wet concrete is caustic)
You'll find most of these at Bunnings or Mitre 10, and bagged concrete mix is widely stocked at both.
Planning Your Edging
Decide on the width and depth of your edging first. A typical garden bed edge is:
| Dimension | Recommended range |
|---|---|
| Width | 75–150 mm |
| Depth | 75–100 mm |
| Height above ground | 25–50 mm |
For curved garden beds, use flexible hardboard or thin plywood as formwork rather than rigid timber. Mark out your line with a hose or rope before you dig — this helps you visualise the shape.
Preparing the Trench
- Mark your line using string or a garden hose.
- Dig a trench to your chosen depth plus 25–50 mm for a compacted gravel base.
- Compact the base — a 25–50 mm layer of compacted AP20 (all-purpose) gravel helps with drainage and prevents the edging from sinking over time. NZ's variable soils, particularly in wetter regions like Northland or the West Coast, make this step especially important.
- Set your formwork on both sides of the trench, secured with timber stakes. Check it's level along the top edge.
Mixing and Pouring the Concrete
For edging, a standard 1:2:3 mix (1 part cement : 2 parts sand : 3 parts aggregate) works well, or use a bagged general-purpose concrete mix and follow the manufacturer's instructions. Keep the mix on the stiffer side — too wet and it will slump and crack as it cures.
- Pour the concrete into the formwork in sections.
- Rod or tamp it down to remove air pockets.
- Strike off the top with a straight-edged piece of timber.
- Finish with a steel float for a smooth surface, or a wooden float for a slightly textured finish that's less slippery when wet.
Tip: In hot, dry NZ summers, dampen the trench before pouring and cover the finished edging with damp hessian or plastic sheeting for at least 3–4 days to slow curing and reduce cracking.
Expansion Joints and Cracking
Concrete expands and contracts with temperature changes — a real consideration in NZ's climate. Cut or form expansion joints every 1–1.5 metres using a piece of hardboard or a trowel cut while the concrete is still green (partially set). This controls where any cracking occurs and keeps your edging looking tidy.
Removing Formwork and Finishing
Leave the formwork in place for at least 24–48 hours before carefully removing it. Avoid walking on or disturbing the edging for at least 7 days. Full strength is reached at around 28 days.
Once cured, you can leave the concrete natural, paint it with a masonry paint from Resene or Dulux, or apply a concrete sealer to protect it from staining and weathering.
Safety Notes
Wet concrete is caustic and can cause serious skin burns with prolonged contact. Always wear:
- Waterproof gloves
- Safety glasses
- Waterproof boots
- Long sleeves
Wash any concrete off skin immediately with clean water. Refer to WorkSafe NZ for guidance on safe handling of construction materials.
When to Call a Professional
While concrete garden edging is DIY-friendly, consider hiring a qualified landscaper if:
- You have a large or complex project with significant levels changes or retaining elements (note: retaining walls over a certain height may require a building consent — check with your council for the applicable threshold — check with your council and see MBIE Building Performance for guidance).
- Your soil is unstable, waterlogged, or on a slope where drainage design matters.
- You want a decorative or exposed-aggregate finish that requires specialist technique.
- You simply don't have the time or tools to do it properly.
A professional landscaper will get the job done efficiently and with a guaranteed finish. You can find qualified local landscapers on tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
