How to Strain Wire Properly — Getting the Tension Right

If there's one skill that separates a fence that lasts from one that sags within a year, it's proper wire straining. Get the tension right and your fence will stand straight and true through summer heat, winter cold, stock pressure, and the odd kangaroo impact. Get it wrong and you'll be out there re-straining before you know it.

Here's how to do it properly.

WHY TENSION MATTERS

Wire expands in heat and contracts in cold. High tensile wire has some elasticity built in, but it still needs to be strained to the correct tension to perform properly. Too loose, and stock will push through or under. Too tight, and you risk snapping the wire or pulling your strainer posts out of the ground — especially in summer when the wire contracts further as temperatures rise. Wait, it's the other way around — wire expands in heat, so if you strain too tight in winter, summer expansion will cause it to sag. Strain too tight in summer, and winter contraction could snap it.

The sweet spot for high tensile wire is generally around 100-120kg of tension for a single strand. You want the wire firm with a bit of spring to it — if you push it sideways, it should spring back, not stay where you pushed it.

TOOLS YOU'LL NEED

  • Chain strainer (also called a fence strainer or monkey grip) — the most common manual tool
  • Wire spinner for unrolling wire without tangles
  • Fencing pliers — the multi-purpose fencing tool
  • Wire cutters
  • Permanent wire strainers (in-line strainers) for long runs
  • A good pair of gloves — wire will cut you up if you're not careful

THE STRAINING PROCESS

1. SECURE ONE END: Attach the wire to your first strainer assembly. Wrap it around the post at least three times, then use a wire clip or tie it off with tie wire. Some people use gripples or permanent strainers at the post — either method works.

2. UNROLL THE WIRE: Using a wire spinner, unroll the wire along the fence line. Keep it on the ground for now. Never let a roll of high tensile wire uncoil uncontrolled — it'll spring everywhere and someone will get hurt.

3. PULL IT THROUGH: Thread the wire through or along your pickets at the correct height. If you're adding wire above or below mesh, this is straightforward. If you're running plain wire fencing, use the appropriate lug position on your star pickets.

4. STRAIN FROM THE FAR END: At the far strainer assembly, attach your chain strainer to the wire and to the post. Slowly ratchet the tension on. This is where feel matters — you want to see the wire lift off the ground between pickets and come up straight, but not so tight that the pickets start leaning toward the strainer.

5. CHECK YOUR TENSION: A rough field test is to push the wire sideways at the midpoint between two pickets. It should deflect about 50-75mm with moderate hand pressure and spring back cleanly. If it stays deflected, it's too loose. If you can barely move it, it's too tight.

6. TIE OFF: Once you're happy with the tension, secure the wire to the strainer post. Wrap it around the post, pull it back along itself, and use tie wire or a gripple to lock it off. Cut the excess, but leave at least 300mm of tail — you might need to re-strain later.

7. CLIP TO PICKETS: Work along the fence line and secure the wire to each star picket using clips. This keeps the wire at the correct height and prevents it from being displaced by stock.

COMMON MISTAKES

Straining in the heat of the day: Wire is at its longest when it's hot. If you strain to correct tension at 40 degrees, it'll be overtight in winter. Best practice is to strain in the morning or on a mild day. If you must strain in summer heat, back off the tension slightly.

Not enough wraps on the post: One wrap around a strainer post isn't enough. Three wraps minimum. The friction of wire on timber is what holds the tension — more wraps, more friction.

Straining through corners: Never strain wire around a corner. Each straight run should be strained independently, with the wire terminated and re-started at each corner strainer.

Joining wire mid-run with knots: Use proper wire joiners or gripples, never knots. A knot is a weak point that will fail under tension.

Forgetting in-line strainers: On runs longer than 300 metres, install permanent in-line strainers so you can re-tension the wire in future without pulling the whole lot out.

HIGH TENSILE VS MEDIUM TENSILE

High tensile (HT) wire holds tension better and is stronger, but it's stiffer and harder to work with. Medium tensile (MT) is more forgiving and easier to handle. For main boundary fences and anything holding cattle, go HT. For internal paddock divisions and lighter applications, MT is fine.

We stock HT 2.5mm wire in 1500m rolls at $200 and MT 2.5mm at $190 per 1500m roll. That's a lot of fencing per roll, which keeps your cost per metre down.

If you're unsure about anything, come and have a chat with us at Outback Fencing Supplies in Orange. We've been through all the mistakes so you don't have to.

Back to blog