Farm Fencing in Kenya: Why the Corner Carries the Whole Fence

Walk any farm fence more than two seasons old and you can read its history in thirty seconds. The line posts stand where they were put. The corner leans. Every wire out of that corner hangs in a soft curve, and the bottom strand is already touching grass.

That fence did not fail because the wire was cheap or the posts too far apart. It failed because one post was asked to hold back two hundred metres of strained wire with nothing to lean against.

A wire fence is a structure. Some members carry load and some carry almost none, and your money should follow that split. This is where the load goes, how to anchor it, and what to build the fence out of.

Only Two Posts in a Run Are Doing Any Work

Tension is what makes a wire fence work. A tight strand behaves like a spring: stock leaning on it meet resistance and the wire returns when they step back. That tension is anchored at the ends of the run and at every change of direction.

Those anchors are strainers, also called straining or end posts. A strainer carries the sum of the pull in every strand, all of it horizontal and all of it arriving near the top, where leverage against the post is worst.

Everything between is a line post, and it has one job: hold the wires at the right height. It takes almost none of the longitudinal load, because the wire passes it rather than ending on it.

A corner is harder than an end. The two runs pull in different directions and the combined pull points outward along the line that splits the angle. That is why a corner needs a stay down each fence line, not one.

Setting a Strainer So It Cannot Lean

A strainer does not fail by sliding through the soil. It fails by rotating: the top walks toward the fence, the bottom kicks back, and the pivot sits below the middle of the buried length. Once the top moves fifty millimetres, every wire in the run is slack.

Depth resists that rotation and matters more than anything else: soil resistance to overturning climbs steeply with depth, so another two hundred millimetres in the hole beats a bag of cement near the surface. Bury about a third of the post. A 2.4 metre strainer set 800 to 900 millimetres deep leaves roughly 1.5 metres of fence. Use 125 to 150 millimetre sections for strainers against 75 to 100 for line posts, and ram the backfill in layers, because loose backfill is the same as no backfill.

Then fit the stay. A stay is a shorter post running from a notch near the top of the strainer down to a block bedded in the ground, in line with the fence and on the side it pulls toward. It works in compression: the wires push the top over, the stay pushes back.

Two details decide whether it works. The stay must meet the strainer high, above the middle of the wire pull, or it has no leverage. And its foot must bear on something solid: a stay block, a flat stone, or undisturbed soil at the bottom of a cut seat. A foot in loose backfill drives itself into the ground, and so does a stay set too steep.

The alternative is a box brace, or H brace: two posts a couple of metres apart in the fence line, joined by a rail near the top with a tensioned diagonal wire between them. That diagonal must run from the bottom of the strainer to the top of the second post. Reversed, it helps the fence drag the strainer over.

One rule costs nothing: never strain wire against a strainer until the stay is fitted and any concrete has cured. Many corners are pulled out of plumb on the first day, before the fence has met an animal.

Strained, Not Just Pulled Tight

There is a real difference between a wire pulled tight by three people and a wire that has been strained. Strained means brought to a controlled, sustained tension with a mechanical tool: a chain or monkey strainer, or an in-line ratchet left in the wire.

Why it matters comes down to the wire. High tensile wire works in its elastic range: strained properly it stretches slightly, stores energy and springs back every time something hits it. Left slack it does nothing, because stock push it aside. Mild steel has a lower yield point, so it cannot be taken as high, and overdone it takes a permanent set and never recovers.

Work one wire at a time. Secure it at one strainer, strain from the other, and watch the anchor as the first two wires come up. If the strainer moves at all, stop and fix it.

Leave a margin. Steel changes length with temperature, and a fence strained bar tight at midday is noticeably tighter at four in the morning. Over-tensioned fences break at joints, pull staples and drag corners. In-line tension springs earn their cost on long runs: they gauge tension visually, absorb the shock of stock or a falling branch, and take up daily expansion instead of passing it to the strainers. Expect one re-tensioning a few months in.

Two things not to do. Do not tension with a vehicle: the load is uncontrolled, and a snapped strand travels fast enough to be dangerous. And do not drive staples home hard on line posts. A flattened staple pinches the wire and starts a fatigue break at that point. Drive them at a slight angle so the legs miss the same grain line, and leave them just off the wire. Fencing pliers and a proper strainer belong with your workshop tools.

Plain, Barbed and Chain Link Do Three Different Jobs

Plain wire is the structural member. It is what you strain, what carries tension and what holds the fence in shape. It does not injure stock, it takes tension hard, and with droppers between posts it gives the cheapest strong fence per metre.

Barbed wire is a deterrent, not a barrier. The barbs stop an animal leaning and rubbing; they do not stop a determined one. It cannot be strained as hard as plain high tensile wire, it damages hides, which is real money on beef and dairy cattle, and it is dangerous around horses. Its place is a top or bottom strand on an otherwise plain wire fence.

Chain link is a barrier and a screen, and the one installed wrongly most often. It is a fabric, not self-supporting, and it does not become a fence by being nailed to posts. It hangs on tensioned line wires, top, bottom and usually middle, strained between proper strainers exactly as a plain wire fence would be, then tensioned across its width against a stretcher bar. Stapled straight to posts over slack line wires it sags, bags out and rolls up along the bottom within a season. Weld mesh is stiffer where you need to hold poultry or small stock.

Droppers, or battens, change the economics. A dropper holds the wires at correct spacing without going into the ground. It carries no load, costs a fraction of a post, and lets you widen post spacing without the wires splaying.

Treated Timber, Concrete or Steel

Treated timber is the default, and its service life depends entirely on the treatment being real. Pressure treatment drives preservative into the sapwood to a specified retention. Dipping or brushing leaves a film, and a film is not a treatment: termites find the untreated wood behind it. Look at the end grain, where genuine treatment shows as a coloured band through the sapwood.

Concrete posts are immune to termites and rot, which in much of Kenya settles the argument. They come precast with holes for wire, since you cannot staple to them. They are heavy, brittle when dropped, and they snap rather than lean when struck, so keep them for line posts unless the strainers are reinforced for bending.

Steel posts, whether angle iron, Y posts or galvanised tube, are strong in bending, quick to drive and cannot be eaten. Their weakness is corrosion, concentrated in one place: the ground line, where the steel wets and dries and oxygen is plentiful. Painted angle iron rusts through there while the rest still looks new. Galvanising lasts far longer, and a bitumen coat over the buried section is cheap insurance, especially at the Coast.

One decision gets made carelessly: whether to concrete posts in at all. A well rammed post is often better, because it can be replaced, and because a collar finishing flush with the ground forms a cup that holds water against the post at the worst possible height. If you concrete, dome the collar and bring it above ground level.

Spacing, and Where the Strainers Go

Line post spacing on flat ground for a plain wire stock fence is commonly 3 to 5 metres with droppers between. Close it up on rough ground, on curves, where stock congregate at water and gates, and for chain link, which needs support at around 2.5 to 3 metres.

Strainers are a geometry question, not a spacing one. You need one at every end, change of direction, gateway and significant change of gradient. That last one gets missed. Where the fence crosses a crest the wires want to lift, so that post must be anchored against uplift; in a dip they pull down, so that post must be substantial. Skip either and the fence pulls itself straight between the high points, leaving a gap underneath.

On long runs, break the fence into strained sections rather than straining a kilometre in one go. Around 150 to 200 metres is sensible. Longer sections gather friction at every post, so the far end never reaches the tension you think you applied.

Wire spacing follows the animal. Cattle need fewer strands set wider apart, with the top strand high enough that they do not reach over. Sheep and goats need strands close together low down, because both go under before they go through. Where goats are involved, mesh is usually the honest answer.

Where Fences Fail First

Fences fail in a predictable order, which tells you where an hour of inspection is worth spending.

The corner, first and nearly always. An unstayed strainer leans, every wire in both directions goes slack, and the fence stops working while still looking like a fence from a distance. Sight along your corners once a year.

The ground line, second. Timber rots and termites attack in the top of the buried section where moisture and air are both available, and steel corrodes in the same band. A post can be sound at the bottom of the hole and gone at the surface.

Gateways, third. A gate hangs off one post and swings on it, taking a changing cantilever load no line post can handle. Gate posts must be strainers in their own right, and the fence anchored at the gate rather than run through it.

Water crossings, fourth. A fence strained across a gully collects debris in the first heavy rain and takes the run with it. Use a floodgate that can swing or break away.

Joints and the bottom wire, constantly. A badly made joint is the weak point in any strand, particularly on high tensile wire where a wrapped and twisted joint slips. Use a figure of eight knot or a crimped sleeve. And walk the bottom wire, the one that ends up buried in grass and rusting.

None of this is expensive. Wire, staples, strainers and fencing tools carry current prices on our price list, alongside the rest of our farm equipment. What separates a fence that stands fifteen years from one that sags in two is where the budget went, and whether anybody fitted the stay.

Frequently Asked Questions