Barbed Wire Tensioning

Before you start, make sure you know exactly where the boundary runs. If it is unclear, check your title documents or have the boundary surveyed. That costs far less trouble than a dispute with a neighbour later. Depending on height, location and type of fence, local building or planning rules may apply. Check with your local building authority before you begin. Also think about people passing by. Barbed wire next to a footpath, road or public space can injure someone, and as the owner you may be held responsible. In some places it is restricted or not allowed at low height next to public areas.

Tensioning only starts once the posts are set and any concrete has fully hardened. The usual method looks like this:

1. Anchor the start of the wire firmly to a corner or end post, preferably with several wraps and a clamp.
2. Run the wire out along the fence line and hang it loosely on the hooks or clips of the intermediate posts.
3. Fit a tensioner at the far end and tighten the wire gradually, without jerking it.
4. Check that the wire runs straight and does not catch anywhere, then fix it securely to every post.
5. With several strands, tension each strand separately and keep the same vertical spacing between them.

Why do corner and end posts matter so much? The whole pulling force of the wire rests on them. That is why they usually get diagonal struts, which stop the post from leaning into the run as the wire is tightened.

Barbed wire varies in core thickness, barb spacing and surface finish. For permanent fencing, galvanised wire is almost always used. Cheaper wire with a thin zinc coating rusts sooner and snaps more easily under tension. Plastic-coated wire is usually chosen where appearance matters.

• Tensioners let you tighten the wire in a controlled way and re-tension it easily when it slackens.
• Steel posts are a common choice for a sturdy, economical fence.
• Concrete posts are heavier and suit long runs and higher loads.
• Timber posts are typical for livestock fencing and temporary fences.
• Cranked arms, angled extensions on top of the posts, carry the wire at an angle and make climbing over harder. They are used where security of the property comes first.

Small fittings such as clamps, binding wire and clips are often overlooked. In practice, they are what keeps the wire in place.

The simplest case is level ground, evenly spaced posts and good access along the whole line. Posts are usually about two to three metres apart. With regular spacing, the wire tensions easily and evenly.

The job takes longer and costs more mainly because of:

• slopes or uneven ground, where the wire has to run in sections with extra anchor points,
• many bends and corners, because each corner is a separate straining point with its own strut,
• more strands, or fitting wire onto cranked arms at height,
• an overgrown strip along the fence, shrubs and poor access,
• removing old, rusty wire before the new wire goes up.

A few errors come up again and again:

• Too little tension. The wire waves about, rubs against the posts in the wind and is easy to get past.
• Too much tension. The wire has no slack to contract in frost and may snap or pull the end post out.
• Corner posts without struts, or set too shallow. Over time they lean and the whole run goes slack.
• Pulling the full length in one go instead of tightening gradually. The tension then ends up uneven.
• Working without gloves and safety glasses. A tensioned wire that springs loose can badly injure hands and eyes.

Temperature matters too. Wire tensioned on a hot summer day contracts in winter and gets even tighter. So it should never be pulled up as far as it will go.

If you have a low fence with firmly set posts, you can do the tensioning yourself. You need heavy-duty work gloves, safety glasses, a tensioner or wire strainer and wire cutters. Leave cranked arms and tall fences to a professional.

1. Put on sturdy clothing with long sleeves, gloves and safety glasses.
2. Check that the corner and end posts are solid and strutted.
3. Wrap the end of the wire around the end post and secure it with a clamp or binding wire.
4. Unroll the wire slowly, ideally with the coil on a bar, so it does not twist or tangle.
5. Hang the wire loosely on the clips of the intermediate posts at the same height.
6. Attach the tensioner at the far end and tighten the wire gradually in several short movements.
7. Test the tension by pressing with a gloved hand: the wire should give slightly but not visibly sag.
8. Fix the wire firmly to each post and cut off spare ends so nothing sticks out.
9. Check the tension again after a few weeks and re-tension if needed.

When you accept the work, walk the whole fence line and check these points:

• The wire is straight along its full length, with no waves or sagging
• It gives slightly when pressed but is not strained to breaking point
• Corner and end posts stand upright and have struts
• The wire is fixed to every post and does not slip anywhere
• Strands sit at consistent heights with even spacing
• Tensioners are accessible for re-tensioning later
• Wire ends are bent back and do not stick out
• The galvanising shows no damage from tools