Tying steel reinforcing bars (rebar) correctly is essential for strong, durable concrete work that meets the NZ Building Code. Done right, it keeps your steel mesh or bar cage in the correct position while concrete is poured, ensuring the finished slab, footing, or wall performs as designed. While basic rebar tying is a skill a capable DIYer can learn, any structural concrete work — especially for foundations, retaining walls, or anything requiring a building consent — should be designed by a qualified engineer and inspected before the pour.
What You'll Need
Before you start, gather the right gear:
- Rebar (reinforcing bar) — typically deformed (ribbed) bar in grades and sizes specified on your engineer's drawings
- Tie wire — standard 1.6 mm annealed (soft) steel wire, sold in coils at most hardware stores
- Rebar tying pliers (also called hook pliers or rebar tying tool) — a purpose-made tool with a hooked end that twists wire quickly and cleanly
- Wire cutters or side-cutters
- Bar chairs or spacers — plastic or concrete supports that hold rebar off the ground at the correct cover distance
- Tape measure and chalk line
- Safety gloves and eye protection — cut wire ends are sharp
You can find tie wire, bar chairs, and basic rebar tying tools at Bunnings, Mitre 10, or PlaceMakers.
Understanding Cover and Spacing
Before tying anything, check your plans. Concrete cover — the distance between the rebar and the concrete surface — is critical for corrosion protection and fire resistance. Your engineer's drawings will specify minimum cover, which is commonly:
- 40 mm for slabs on ground in normal conditions
- 50–75 mm for exposed or coastal environments
- More for structural elements — always follow your specific drawings
Bar spacing (the gap between parallel bars) is also specified on your plans. Typical slab mesh or bar spacing is 200–300 mm centres, but this varies. Never guess — use the engineer's drawings.
How to Tie Rebar: Step-by-Step
1. Position Your Bars
Lay out the bars according to your plans, checking spacing with a tape measure. Place bar chairs or spacers underneath to achieve the correct cover from the ground or formwork.
2. Cut Your Tie Wire
Cut lengths of tie wire approximately 300–350 mm long. With practice, you'll judge the right length for a neat, tight tie. Many concreters pre-cut a bundle before starting.
3. Wrap the Wire Around the Intersection
Fold a length of wire in half to create a loop. Place the folded wire diagonally under the intersection of two crossing bars, then bring both ends up and over the top, threading them through the loop.
4. Twist with Your Hook Tool
Insert the hook of your rebar tying pliers into the two loose wire ends and rotate the tool — typically 3–4 full twists — until the wire is snug and firm against both bars. The bars should not rattle or shift. Don't over-twist or the wire will snap.
5. Bend the Tail Down
Bend the twisted wire tail flat against the bar or inward, away from the concrete surface. Protruding wire ends can cause rust staining or corrosion paths if they reach the surface.
6. Repeat at Every Intersection (or as Specified)
For most structural work, tie every intersection in the perimeter zone and alternate intersections in the interior field — but follow your engineer's specification. In high-wind or seismic zones (common in NZ), more ties may be required.
Common Tie Wire Patterns
| Tie Type | When Used |
|---|---|
| Snap tie (simple loop) | General slab and footing work — most common |
| Saddle tie | Tying bars at an angle or where extra grip is needed |
| Figure-eight tie | Corners and laps where bars cross at odd angles |
| Wrap-and-saddle | Heavy bar (HD16 and above) where extra security is needed |
For most residential work, the snap tie is all you'll need.
Key Tips for Good Results
- Keep rebar clean — remove mud, oil, or loose rust before tying and pouring
- Check cover constantly — bar chairs can shift; recheck before the pour
- Don't stand on tied cages — walk on boards laid across the bars to avoid displacing them
- Lap lengths matter — where bars overlap (laps), the lap length is specified by your engineer; never shorten laps
- Seismic requirements — NZ sits on the Pacific Ring of Fire. Structural concrete must comply with NZS 3101 (concrete structures standard) and your regional seismic zone requirements. This is why engineer-designed reinforcement is so important here
Building Consent and Inspections
Many concrete projects in NZ — including new foundations, retaining walls over 1.5 m, and structural slabs — require a building consent from your local council. Even some Schedule 1 exempt work (minor projects that don't need consent) must still comply with the NZ Building Code. Always check with your council before starting. MBIE Building Performance has clear guidance on what requires consent.
If your project requires consent, a council inspector will typically need to inspect the reinforcing before the concrete is poured. Don't pour until you have that sign-off.
When to Call a Professional
Rebar tying on a small garden path or non-structural slab is manageable for a competent DIYer. However, you should engage a qualified concreter or structural engineer for:
- Any work requiring a building consent
- Foundations, footings, or retaining walls
- Anything in a high-wind or high-seismic zone
- Complex bar bending, lapping, or cage construction
- Situations where you're unsure about the engineer's drawings
Poorly placed or tied reinforcing can lead to structural failure — a risk not worth taking. A licensed concreter will also know how to read structural drawings and meet inspection requirements. You can find qualified local concreters on tradedirectory.co.nz.
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