Measure the Opening Before You Buy Anything

It is tempting to order the gate first and worry about the gap later, but a wooden side gate only works if it fits the opening you actually have. Take a tape measure and record the width at three points: near the top, at the middle and near the ground. Openings are rarely parallel, especially in older British properties where a wall may have shifted or a fence line has settled. Use the narrowest measurement as your working width, because anything that catches will rub for years.

Do the same vertically on both sides. If the ground slopes, note the difference between the highest and lowest point, as this will decide your ground clearance. Then check what lies beneath before you dig. A quick probe with a stout screwdriver or a cane will usually reveal a drain cover, an old brick footing or a hidden irrigation pipe. Hitting a water main with a post hole digger is an expensive way to spend a Saturday.

As a rough rule, allow around 25mm of total clearance between the gate and the posts — roughly 12mm on the hinge side and 12mm on the latch side. This gives the timber room to swell in a wet winter without jamming.

Set the Posts Properly and the Rest Follows

The posts carry the whole gate, so they need to be substantial. For a gate up to 1.8m high, use 100mm x 100mm pressure-treated posts, ideally sunk at least 600mm into the ground. A hole roughly three times the post's width gives enough concrete to resist leverage.

• Dig the holes, then add 100mm of gravel or hardcore for drainage before the post goes in.
• Line up the face of the post flush with the opening, not the centre of the post, so the gate sits neatly within the frame.
• Check plumb with a spirit level on two adjacent faces, then brace the post with timber battens pegged into the ground.
• Check the diagonals between the two posts — if they match, your frame is square.
• Use a fast-setting post mix or a dry 1:4 cement and ballast mix, tamped firm and crowned slightly above ground level so water runs away.

Leave the concrete to cure for at least 24 hours before hanging anything, and longer in cold weather. Sites in the north or west of the UK often face more driving rain, so a slightly higher crown on the concrete and a generous treatment of the post's buried end will both pay off.

Hang the Gate So It Swings Freely

Once the posts are solid, position the gate with the clearance allowances you calculated earlier. Many people find it easiest to rest the gate on timber offcuts or wedges while the hinges go on, which holds it at the right height and stops it wandering.

• Set the bottom of the gate around 50mm above the ground — a little more over gravel or an uneven threshold.
• Fit three 75mm tee hinges for a standard 900mm gate, spaced roughly at the top, middle and bottom of the hanging stile.
• Pilot drill every screw hole. Oak and some dense softwoods split easily, and a split stile is a permanent problem.
• Use galvanised or stainless screws — 60mm is a sensible length into a decent post.

Check the diagonal brace before you commit. On a braced gate, the brace should rise from the bottom of the hinge stile to the top of the latch stile. Fitted the other way round, the gate will sag in a season or two.

Test the Swing Before You Tighten Everything

Open and close the gate through its full arc while the screws are still snug rather than fully torqued. It should move without scraping, catch the latch cleanly and settle back against the post under its own weight. If it drags at the far end, the post has likely moved out of plumb, or the gate itself is slightly out of square.

If the ground slopes along the swing, rising butt hinges are the traditional answer — they lift the gate as it opens, giving clearance where a fixed hinge would scrape. Where a gate binds only in wet weather, resist the urge to plane the edge. Wait for it to dry out and check again; over-planing a swollen gate leaves a permanent gap in summer.

Protection and Simple Yearly Care

Treat the gate before you hang it, not after. Every face, and especially the end grain at the top and bottom of each stile, will soak up water and rot first. Two coats of a good wood preservative or exterior stain, applied to all six sides, will add years to the life of the timber. Recoat cut ends and any fresh drill holes as you work.

Once a year, in early autumn, give the gate a few minutes of attention: oil the hinges, clear leaves and soil from around the base of the posts, and check the screws are still tight. A light sanding and a fresh coat of treatment every two or three years keeps the whole assembly in good order. A well-fitted gate, hung with a little patience, will swing sweetly for a decade or more.