How to Add a Concrete Border Around an Existing Gravel Driveway

Adding a concrete border (also called a mow strip or edging kerb) around a gravel driveway is a satisfying weekend project that keeps gravel contained, defines the driveway edge, and reduces maintenance. Most homeowners with basic DIY skills can tackle this job, though larger or more complex driveways may benefit from a professional driveway layer.

What You'll Need

Before you start, gather your materials and tools:

• Timber formwork (typically 100 mm × 25 mm DAR pine or similar)
• Timber stakes (300–400 mm long) and screws or nails
• Concrete – either bagged ready-mix (e.g., 20 MPa general-purpose bags from Bunnings or Mitre 10) or a ready-mix truck delivery for longer runs
• Reinforcing mesh or bar (optional but recommended for driveways subject to vehicle loads)
• Compactable gravel or AP20 for the sub-base
• Spade, mattock, string line, spirit level, float, edging tool
• Concrete sealer (optional, for a neat finish)
• Safety gear – gloves, safety glasses, and waterproof boots (wet concrete is caustic)

As a rough guide, a border around 100 mm wide × 100 mm deep will use approximately one 20 kg bag of concrete per 0.3–0.4 linear metres, though this varies by brand and mix. Check the bag for coverage details.

Planning and Consent Considerations

For most residential concrete edging work, a building consent is not required under Schedule 1 of the Building Act 2004. However, rules vary by council and site, so always confirm with your local council before starting. If your driveway crosses a legal road boundary or connects to a public footpath, you may need a vehicle crossing permit from your council — this is separate from building consent.

Check MBIE Building Performance for general guidance on what work requires consent, and contact your local council directly to confirm your specific situation.

Step 1 – Mark Out the Border

Use a string line and pegs to mark the inside edge of your new concrete border along both sides of the driveway. A typical border is 100–150 mm wide and 75–100 mm deep, though you can go wider for a more decorative look. Keep the border consistent in width for a tidy result.

Step 2 – Excavate the Trench

Dig a trench along each marked line to the required depth. You want at least 75 mm of concrete sitting on a 50 mm compacted gravel sub-base (AP20 or similar). Remove any grass, roots, or soft material. Compact the base firmly — a hand tamper works for small jobs, or hire a plate compactor for longer runs.

Tip: Keep excavated soil away from the gravel driveway to avoid contaminating it.

Step 3 – Set Up Formwork

Cut your timber to length and fix it along the trench edges using timber stakes driven into the ground every 600–900 mm. Use a spirit level to ensure the top of the formwork is at your desired finished height — typically flush with or just above the existing gravel surface. Screw or nail the boards to the stakes securely; concrete is heavy and will push formwork out if it isn't well braced.

For curved sections, use thinner ply (6–9 mm) or make a series of short straight sections to approximate the curve.

Step 4 – Add Reinforcing (Recommended)

For a border that will be driven over or sits in an area with vehicle loads, lay SL62 or SL72 mesh or a single 10 mm deformed bar along the centre of the trench. Support it on small stones or plastic bar chairs so it sits roughly in the middle of the concrete depth — this is called cover and protects the steel from corrosion. BRANZ has useful guidance on concrete best practice for residential work.

Step 5 – Mix and Pour the Concrete

For small jobs, bagged concrete mixed in a barrow or hired mixer is practical. Follow the manufacturer's water-to-mix ratio exactly — too much water weakens the concrete significantly. For runs longer than roughly 15–20 metres, consider ordering ready-mix concrete (specify 20 MPa, 20 mm aggregate) from a local supplier, as this saves time and ensures a consistent mix.

Pour the concrete into the formwork in sections, rodding or tamping it down to remove air pockets. Strike off the top with a straight-edged board, then finish with a wooden or magnesium float for a smooth surface. Use a concrete edging tool to round off the top edges — this reduces chipping over time.

Step 6 – Curing and Finishing

Curing is critical. Cover the fresh concrete with plastic sheeting or damp hessian for at least 3–7 days, especially in hot or windy NZ summers. Avoid letting it dry out too fast, which causes cracking. Do not allow vehicle traffic on the border for at least 7 days, and ideally 28 days for full strength.

Once cured, remove the formwork carefully. You can apply a concrete sealer to protect the surface and improve appearance — products are available from Bunnings, Mitre 10, or PlaceMakers.

Step 7 – Backfill and Tidy Up

Once the formwork is removed, backfill any gaps on the outside of the border with soil or lawn mix and compact lightly. Top up the gravel on the inside edge if needed to bring it level with the new border.

When to Call a Professional

Consider hiring a qualified driveway layer or concreter if:

• Your driveway is long (over 20–30 metres of edging) and ready-mix logistics become complex
• The ground is unstable, on a slope, or has poor drainage
• You need to tie into an existing concrete driveway, footpath, or kerb
• You're unsure about sub-base preparation or reinforcing requirements

A licensed tradesperson will also be required if any stormwater drainage work is involved — drainlaying is restricted work under the Plumbers, Gasfitters, and Drainlayers Act and must be carried out by a licensed drainlayer registered with the PGDB.

You can find experienced local driveway layers and concreters on tradedirectory.co.nz.

Sources & Further Reading

• MBIE Building Performance – Building Consent Exemptions
• BRANZ – Concrete and Construction Guidance
• Plumbers, Gasfitters and Drainlayers Board – Restricted Work
• Bunnings – Concrete and Driveway Products
• Mitre 10 – Concrete and Landscaping
• PlaceMakers – Concrete and Building Supplies