Why sloping ground changes the rules

A fence on flat ground is forgiving. A fence on a slope is not. Gravity, water and livestock all work against you, and the steeper the ground, the more quickly a loose wire or a shallow post reveals itself. On a 1 in 4 slope you are not just building a barrier, you are building something that must resist animals leaning downhill, soil creeping, and rainwater running along the wire line.

The first decision is the line itself. Resist the temptation to run a boundary straight up and down the hill simply because it looks tidy on a plan. A fence that climbs directly up a slope ends up with long, sagging spans, and stock will test the low side where the wire lifts off the ground. Where you can, follow the contour in gentle dog-legs, or run diagonally so the fence sheds water rather than damming it.

Getting the strainers right on soft, sloping ground

Everything downstream depends on the strainers. On slopes, the pull on a corner or end post is greater and rarely square to the ground, so bracing needs to be generous. Set strainers at least 750–900mm deep in firm subsoil, deeper in peat or sandy ground, and use posts of 125mm diameter or more.

• Use a box brace or double angle brace at every corner, end and change of direction.
• Brace downhill-facing posts from the uphill side, where the ground naturally supports the strut.
• On steep ground, add a diagonal stay or a ground anchor rather than relying on a single strut.
• Cut a drainage notch in heavy clay so water does not sit around the post base and rot it.

If you are fencing a long slope, put a strainer every 100–150 metres. It costs extra posts but saves you from endlessly retensioning a single over-stretched run.

Post-and-rail: handsome, but demanding

Post-and-rail suits the boundaries people actually look at — roadside frontages, public footpaths, gateways. On slopes it works well provided you accept that each bay needs to be set individually. Rails can follow a gentle gradient, but on anything steeper than about 1 in 8 you will be cutting rails at angles or stepping the fence in short flights, which is time-consuming and uses more timber.

Aim for intermediate posts every 2.5–3m rather than the 3.5m you might get away with on the flat. Keep the bottom rail no more than 250mm off the ground so sheep and youngstock cannot push underneath, and use half-round or square rails of at least 87mm to resist leaning cattle. Treated softwood gives a decade or more if the cut ends are properly dipped.

Stock netting: the workhorse for sheep and mixed grazing

Woven stock netting is usually the most cost-effective way to hold sheep and lambs on uneven pasture, but it is unforgiving of hollows. The classic failure is a gap under the net in a dip, which lambs find within a day.

• Use 1.05m netting for sheep, 1.2m or more where deer or larger stock are present.
• Space intermediates at 3m on slopes, closer in soft going and at every pronounced change of level.
• Drop a post into each hollow so the net follows the ground rather than bridging it.
• Fix netting to the strainers with staples and tension it in stages, working from both ends towards the middle.

On very broken ground, a single line of netting can be backed up with a strand of plain wire at the top to discourage leaning and to take some of the strain off the net itself.

Electric fencing: the flexible answer for awkward terrain

Electric fencing copes with slopes better than anything else because the wire does not need to be dead straight or drum-tight to work. It is also the cheapest way to subdivide a hillside for rotational grazing.

Two or three strands will hold cattle; sheep need at least three, with the bottom strand 150–200mm up and the top at about 750mm. On steep ground, keep spans short — 4–5m between posts — so the wire cannot bow away from the animal's nose. Plastic posts with a foot plate hold better than plain spikes in stony or peaty soil.

Power is where most systems fail. Damp grass, long runs and dry summer ground all sap voltage. Aim for at least 4–5kV at the far end of the fence, and drive earth stakes into permanently damp soil, never into a dry bank. On a sloping site, place the earth system at the lowest, wettest point you can reach; one stake per joule of energiser output is a sensible starting rule. Keep vegetation off the bottom wire with a strimmer or a dose of glyphosate under the line.

Gates, corners and keeping it standing

Gateways on slopes are the classic trouble spot. Hang the gate so it swings uphill and away from the strain, use a heavier gate post with extra bracing, and consider a concrete footing where the ground is soft. A gate that droops within a season is almost always a bracing problem, not a hinge problem.

Finally, walk the fence after the first hard rain and again after the first frost. Ground movement on slopes is constant, and tightening a stray staple or resetting a lifted net in October is far easier than catching a lame lamb in February. Good fencing on uneven land is less about brute strength and more about reading the contours and working with them.