Kumar IronUpdated
In this guide
Which binding wire
The common choice for tying TMT reinforcement is annealed, soft black wire of about 18 gauge (SWG), roughly 1.2 mm thick. It is soft enough to twist by hand or with a hook, and strong enough to hold bars in place while concrete is poured. Thicker 16 gauge is sometimes used for heavy bars and rafts. Check the gauge on the coil label.
Annealed wire is heat-treated to make it soft. Hard, springy wire snaps while twisting and ties loosely. Pull a short length: it should bend and twist fully without cracking.
How much wire per tonne of steel
As a rule of thumb, plan about 8 to 12 kg of binding wire per tonne of reinforcement. Closely spaced steel, many small bars and stirrups, and wasteful tying push the figure up. Large bars with wide spacing come in lower. This is an estimate, not a code figure.
For a slab, a rough planning figure is about 30 to 50 grams of wire per sq ft of slab at typical steel quantities. For a house, add the columns, beams and footings. Order a little extra, because the wire is used up in doubled loops and cutting.
| Steel on the job | Binding wire to plan |
|---|---|
| 1 tonne | 8 to 12 kg |
| 3 tonnes | about 25 to 36 kg |
| 5 tonnes | about 40 to 60 kg |
| 10 tonnes | about 80 to 120 kg |
Use the steel calculator or the how-much-steel guide to find your steel weight first, then multiply.
Rough wire length for the curious
At 18 gauge, one kilogram of wire is roughly 100 to 110 metres. A single tie with a doubled wire uses about 25 to 35 cm, so one kg gives you several hundred ties. That is why the total weight looks small but the job eats it quickly.
Twisting method on site
- Cut the wire into pieces of about 30 cm, or use a coil with a hook tool.
- Double the wire, loop it around the crossing, and twist the ends tight until it grips the bar. Do not over-twist, which weakens the wire.
- Tie alternate crossings on slabs and every crossing at corners and in columns and beams.
- Bend the tail inward so the cut ends do not stick into the cover and cause rust spots.
- Tie stirrups to main bars at every corner, and at the top of each stirrup in beams.
What to check when buying
- Even thickness along the coil.
- Soft, annealed wire that does not spring back.
- Minimal rust in the coil.
- The gauge stated on the label.
- Buy coils, not loose rolls with unknown origin, if you need consistent quality.
Tell the store your steel quantity and we will suggest the coil size. Rates vary, so call or WhatsApp for the current price.
Frequently asked questions
- What gauge binding wire is used for TMT bars?
- Usually 18 gauge annealed soft wire. 16 gauge is used for heavier bars.
- How much binding wire for one tonne of steel?
- As a rule of thumb, 8 to 12 kg. It varies with bar size and spacing.
- Can I use galvanised wire for binding?
- You can, but black annealed wire is the usual and more flexible choice for reinforcement.
- Why does binding wire snap while twisting?
- It is likely hard, not annealed, or it was over-twisted. Choose soft wire and twist just to grip.