Start with the Slope, Not the Gate

Gates on the level are forgiving. Gates on a slope are not. Before you buy anything, take a good look at the ground you are working with: how steep is the fall, and does it run along the fence line or away from it? A gentle one-in-twenty gradient is straightforward. A drop of 200mm across a 900mm opening is a different problem altogether, and it will dictate your hinge choice, your latch and even the shape of the gate itself.

Run a string line between the two post positions and check it with a spirit level. Measure the fall at the gate opening, not somewhere vaguely nearby. Note also whether the ground continues to fall beyond the gate — if a path slopes away sharply, the bottom of the gate may need extra clearance so it never scrapes when the ground swells in winter.

The single most common mistake is ordering a rectangular gate for a sloping opening and then fighting it for years. As a rule of thumb: if the fall is under about 50mm, a standard rectangular gate with the bottom rail cut to follow the slope will do. Anything more and you want a gate built with a raked or stepped bottom rail, made to the actual measurements of the opening.

Setting the Posts Properly

Hinges can only correct so much. If the posts move, the gate will follow. On sloping ground the temptation is to leave the lower post short, and this is where trouble starts.

• Dig each post hole to a minimum of 600mm deep, or a quarter of the post length, whichever is greater. On clay or ground that holds water, go deeper and wider.
• Use a post that is at least 100mm square for a gate up to 1.2m wide, and 125mm square for anything heavier. Oak, sweet chestnut or pressure-treated softwood all work well.
• Set the bottom of the post on a bed of compacted hardcore, not bare soil, so water drains away rather than pooling around the timber.
• Concrete both posts in, and check them for plumb with a level in two directions, not one. Slope does not excuse a leaning post.
• Bring the tops of the posts to the same height if you want a level head, or follow the slope if that suits the garden better. The important thing is that the hinge post and the latch post sit in the same plane, so the gate closes squarely rather than twisting.

Leave the concrete to cure for at least 48 hours, and preferably a week, before hanging anything on it. Hanging a heavy gate onto green concrete is a reliable way to shift the post and undo your careful work.

Adjustable Hinges Do the Heavy Lifting

This is where sloping ground becomes manageable. Adjustable hinges let you raise, lower, tilt and swing the gate after it is on the post, which is exactly what you need when the geometry is awkward.

Look for hook and band hinges with a threaded adjustment, or cranked band hinges that offset the gate from the post. Cranked hinges are particularly useful where the ground falls across the opening, because they let you set the gate slightly proud of the post and swing clear of rising ground. Rising butt hinges, which lift the gate as it opens, are excellent on a slope, though they need a gate light enough for their capacity.

Fit three hinges rather than two on anything wider than 900mm or heavier than about 25kg. Hang the gate on temporary blocks first, packed to the height and angle you want, then mark the hinge positions and fix them with galvanised or stainless steel screws. Aim for 10–15mm clearance at the bottom and around the sides; on sloping ground, err on the generous side.

Choosing a Latch That Still Catches

A latch that works perfectly on flat ground can miss entirely when the gate sits at an angle. Two things matter: the latch must tolerate a bit of vertical movement, and it must be easy to reach from both sides.

• Adjustable catches have a slotted backplate so you can slide the keep up or down to meet the latch bar precisely.
• Spring-loaded gate latches with a generous throat cope better with a gate that drops slightly when it swings.
• Drop bolts into a socket set in a concrete pad work well on the low side of a sloping gate, where a conventional catch would have nothing solid behind it.
• Double-sided handles save a lot of walking round, and on a steep drive that matters more than you might think.

Set the latch last, once the gate is hanging and swinging correctly. Fit it in the closed position and let the gate tell you where the catch belongs.

Timber Care on Uneven Ground

Gates on slopes tend to sit closer to damp ground at one end, and that is exactly where rot begins. Keep the bottom rail at least 50mm clear of the soil, and if the ground is permanently wet, set a concrete pad or gravel apron beneath the swing.

Treat any cut ends and drilled holes with a brush-on preservative straight away — end grain soaks up water faster than any other surface. Give the gate and posts a coat of a breathable wood stain or oil every 12 to 18 months, and check the fittings at the same time. Rusting screws and hinges loosen, and a gate that starts to sag is harder to correct than one that never did.

Finally, watch the seasons. Timber swells in a wet British winter and shrinks in a dry summer, so a gate that rubs in January may clear perfectly by June. Set your clearances with that in mind, and you will spend far less time out there with a plane and a spanner.