How to Build a Stock Fence: Posts, Netting, Tensioning and the Law

Ask any good fencer and they will tell you the same thing: a stock fence lives or dies at its ends. The netting in the middle does very little work. It is the strained end posts and their bracing that hold everything tight, and if those are solid, a well-built fence will shrug off leaning cattle and jostling sheep for twenty years. If they are weak, the whole run goes slack within a season. So most of the skill, and most of this guide, is about doing the ends properly and then tensioning the wire correctly between them.

This is a practical how-to, but it also has a legal side that catches people out. Keeping livestock brings a genuine duty to stop your animals straying, especially onto a road, and there are real rules about barbed wire next to a public path and about who is responsible for a boundary. Those parts are not just good manners, they are the law, so we have set them out carefully with the sources further down. Treat the legal section as general guidance, not legal advice, and check your own deeds and your local council before you rely on it.

Plan the fence line first

Before you order anything, walk the line. Decide where the straining posts, corners, gateways and any stiles will go, because that dictates how much material you need and stops you making a second trip to the supplier. Straining posts are the expensive, heavy ones and you want a strong one at every end of a run, at every corner, and at every marked change of direction or gradient. On a long straight run you need far fewer than people expect: the government fencing specification allows up to 150 metres between strainers on mild steel line wire and up to 300 metres on high-tensile wire.

Think about the ground too. Fencing into a pronounced dip pulls posts upward when you tension the wire, so a low point often wants a longer, deeper post to stop it jacking out. Follow the natural contours by eye and the finished fence will look right as well as hold.

Materials: posts, wire and netting

Posts and timber

Use pressure-treated softwood, fully peeled and treated. The one detail worth insisting on is the treatment rating: timber that goes into the ground must be rated for ground contact (look for UC4 or HC4). Cheaper UC3 or HC3 timber is not meant to touch the soil and will rot early. Creosote-treated posts are the traditional gold standard and last longest, and while creosote has not been sold to the general public since 2003, farmers and fencing suppliers can still buy pressure-treated creosote posts.

For a post-and-wire or netting fence, the government specification gives sensible minimum sizes:

• Straining posts: at least 125 by 125 millimetres square, or a 100 millimetre top diameter if round, and long enough to set at least 750 millimetres into the ground. A common contractor's choice is a round post roughly 150 to 180 millimetres across, driven deep, with around 1.15 metres standing proud for a cattle fence.
• Struts (braces): around 75 by 75 millimetres, mortised into the straining post.
• Intermediate (line) posts: around 75 by 75 millimetres square, or a 65 millimetre top diameter, set at least 600 millimetres into the ground and no more than 3.5 metres apart.

Wire: mild steel or high tensile

Stock netting comes in mild steel or high-tensile versions, and the choice matters more than it looks.

	Mild steel	High tensile
Tensioning	Does not need to be strained as tightly	Strains much tighter, springs back
Post spacing	Closer posts needed	Can space posts wider, so fewer of them
Best for	Lots of turns, or fences backed by a hedge	Long runs, maximum strength and longevity
Maintenance	More re-tensioning over time	Spring keeps the net tight, less upkeep

If the budget stretches to it, high-tensile netting is usually the better buy: it is stronger, lasts longer, can be pulled tighter and needs fewer intermediate posts to hold its shape.

Reading the netting code

Netting is sold by a code such as C8/80/22, and once you can read it, choosing the right roll is easy. The letter or letters tell you the wire type and knot (for example C is a heavier mild-steel hinge-joint net, HT is high tensile). The first number is the number of horizontal line wires, the second is the overall height in centimetres, and the third is the spacing in centimetres between the vertical stay wires. So:

• C8/80/15 is mild steel, 8 wires, 80 centimetres tall, stays every 15 centimetres. The close 15 centimetre stay makes a tighter mesh, often chosen for sheep and lambs.
• HT8/80/22 is high tensile, 8 wires, 80 centimetres, stays every 22 centimetres, a strong, economical general net.
• L8/100/15 is a lighter mild-steel net at a full metre tall.

As a guide, a closer stay spacing suits smaller and more determined animals, while a wider stay is cheaper and fine for cattle. Match the height and mesh to what you are keeping: sheep and lambs want a tight lower mesh, and goats, which climb and jump, want a taller net again, typically 1.05 to 1.2 metres or more.

Staples, top wire and tools

Buy galvanised barbed staples: they grip far better than plain ones and barely cost more. For a livestock-proof height, plan to run one or two strands of plain or barbed wire along the top of the net to bring the finished fence to at least 1.05 metres. For a cattle fence, two strands of barbed are usual; one is often enough over sheep netting. The kit you will want on the day is a post knocker (or a good maul), a spade, a fencing tool, quality wire cutters and a ratchet straining clamp with chains.

Building it, step by step

The order of work is what keeps a fence tight. Do the strained ends and their bracing first, get a bottom line to work to, drive the line posts, then hang and tension the net.

Putting up a stock fence, in order

1. 1

   Set the straining posts

   Drive a solid straining post at each end of the run, deep enough that it will not shift when you crank up the tension. Do the same at every corner and change of direction, using a proper turning post rather than trying to turn on a light line post.

2. 2

   Brace each strainer

   Cut a shallow notch into the straining post about 450 millimetres off the ground (too high and the strut jacks the post out; too deep and you weaken the post). Dig a small trench for the strut foot, set a short timber bearer in it, then wedge a diagonal strut tightly between the bearer and the notch. A diagonal strut set into the ground beats a strut simply braced against the next post, which will not last.

3. 3

   Run a bottom line

   Strain a single plain wire between the ends, about 25 millimetres off the ground. It gives you a line to set the posts to and cheaply adds height at the base.

4. 4

   Drive the line posts

   Space the intermediate posts no more than 3.5 metres apart (many people work to about 2.5 to 3.5 metres; experienced contractors on high-tensile wire go wider). Follow the ground contours and, in a dip, use a longer post so it will not lift when the net is tensioned.

5. 5

   Hang and join the net

   Wrap the net around the first straining post and tie it off with half-hitch knots, leaving long tails so it can slide and pull tight. Keep the wire centred on the post. To join two rolls, tie a neat run of half-hitch loops down one edge and thread the tails of the next roll through them, with no kinks.

6. 6

   Tension it

   Hook a ratchet strainer and chains onto the far end and crank slowly. Watch the crimps built into the wire: when they have pulled out by about two-thirds, stop. Pull them out completely and the net loses its spring.

7. 7

   Staple and top off

   Fix the net to each line post with barbed staples, driven almost home but not so far that they crimp the wire. Then run your top strand or strands: on a cattle fence, set the first barbed wire about 50 millimetres above the net to stop cattle pushing their noses under it, with roughly a 125 millimetre gap to the second.

Gates

The golden rule with gates is that you never strain a fence off a gatepost, because the pull will drag it out of line over the years. Instead, put a proper straining post about a metre away from the gatepost and fill the short gap with rails. Hang the gate from its own posts, set well in: at least 900 millimetres deep in a concrete surround (around 450 by 450 millimetres and 600 millimetres deep), or, without concrete, at least 1.1 metres deep with the soil rammed back in firm layers. Cap the tops so water runs off, and match the gate height to the fence beside it.

Electric fencing: the quick version

Electric fencing earns its keep for temporary paddocks, strip grazing and rotational systems, and as a "psychological" backup on a permanent fence. It works by teaching the animal to respect the line after a shock or two, so it does not have to be a physical barrier.

• Cattle are very sensitive: a single line at around 90 centimetres works for strip-grazing, though a herd with calves wants two lines.
• Sheep are well insulated by their wool, so they need more lines to feel it: three lines is normal for temporary work, five for a permanent fence. In a five-wire fence, leave the bottom wire un-energised so growing grass does not short it out.
• Pigs are controlled by two or three low lines. Poultry and pigs are often best protected from foxes with electric netting, which gives blanket coverage from the ground up.

Whatever the stock, keep vegetation off the bottom live wire, because grass touching it leaks the charge to earth and weakens the whole fence, and use an energiser rated comfortably above your fence length. A permanent electric fence still needs proper strained ends and a good earth stake.

Your legal duties as a stock keeper

This is the part that turns a fencing job into a legal one. None of it is complicated, but it is worth getting right. The rules below are for England, with Wales largely the same; Scotland and Northern Ireland have their own statutes, flagged at the end.

Nation by nation

The building techniques are the same across the UK, but the law is not. The Animals Act 1971 and the Highways Act 1980 apply in England and Wales. Scotland has its own arrangements, including the Animals (Scotland) Act 1987 for liability and separate roads legislation for matters like barbed wire, and Northern Ireland has its own animals and roads law again. The principles (keep your stock in, do not endanger people on the road, check your deeds for boundary duties) hold everywhere, but the exact statute and wording differ, so confirm the position for your nation before you rely on the detail above.

Maintenance

A fence is not "done" the day you finish it. Walk it after the first hard frost and again after a wet winter, because the ground moves and posts can heave. Re-tension any run that has gone slack, especially mild-steel netting, replace any staples that have popped, and keep the bottom line and any electric wire clear of smothering grass. Watch the strained ends most of all: a strut that has worked loose or a post starting to lean is the early warning that a whole run is about to go, and it is a five-minute fix now rather than a rebuild later.

Before you build: check these

1. Have you planned where every strainer, corner, gateway and stile goes, and ordered enough heavy posts?
2. Is your ground-contact timber rated UC4 or HC4, not UC3 or HC3?
3. Have you chosen a netting grade and height that suits your stock, and worked out your top-wire strands to reach at least 1.05 metres?
4. Will barbed wire be kept off the public side of any boundary next to a road, footpath or bridleway?
5. If you keep livestock, are your boundaries genuinely stock-proof, whoever owns each fence?
6. Do your deeds place any boundary-maintenance duty on you, and is the line clear with your neighbour?
7. Is the fence within the planning height limits, or do you need to check with the local planning authority?

For the legal points, always confirm the current position: the Animals Act 1971 and Highways Act 1980 on legislation.gov.uk, HM Land Registry Practice Guide 40 and your own title documents for boundaries, and your local council or a solicitor if a boundary or right-of-way question is genuinely in dispute.