Before You Reach for the Tape

A made-to-measure driveway gate is a sizeable investment, and the measurements you take in the driveway decide whether it hangs sweetly or fights you for years. Being 30mm out can mean a gate that won't latch, one that looks gappy and rattles in the wind, or worse — one that simply won't fit between the piers. The good news is that measuring properly takes about twenty minutes and a second pair of hands.

You'll need a steel tape measure (cloth ones stretch), a spirit level, a pencil, a notepad and something to mark the ground. Work in millimetres throughout. Gate makers and timber merchants quote in millimetres, and converting at the last minute is where mistakes creep in. Write everything down as you go, take photographs from both sides of the opening, and include close-ups of any walls, kerbs or drains that might get in the way.

Measure the Width at Three Heights

Driveway openings are rarely a perfect rectangle. Brickwork is uneven, old piers have shifted, and rendered walls can bulge in the middle. Measure the gap between your fixing points at the top, in the middle and near the bottom, then repeat the exercise from the other side. If the figures differ, the narrowest one matters most — that's what the gate has to pass through, and possibly swing through.

• Fitting between walls or piers: take the narrowest reading as your working width, and note whether the wall faces are flat or whether there's a plinth or ledge that will foul the gate frame.
• Fitting new posts into the ground: measure the existing opening, then decide whether the posts sit inside that gap or outside it. A post set outside the opening gives you more gate; a post set inside it reduces the clear width by its full thickness.
• Double gates: measure the full opening, then mark where the centre line falls. The two leaves only need to be identical if you want them to be; the gate maker just needs to know where they meet.

Height, Ground Level and Slope

Height is measured from the ground at the gate's closing position up to the top of the opening, and it should be taken at each side and in the centre. Note which reading you're using as your reference, and be honest about the ground — gravel, block paving and decking all move over a season or two. A gate set 20mm above a gravel drive can end up dragging after a wet winter.

Then walk the swing arc before you commit. A gate needs clearance to open, typically 25 to 50mm above the surface at its lowest point, but if the drive slopes up towards the road the gate will catch as it swings unless you allow for it or raise the hinge side. Check the ground beneath the gate too, as a drainage channel or a change in surface level at the threshold is very common and needs accounting for.

Check the Opening Is Square Using Diagonals

Width and height alone won't tell you whether an opening is square. Measure the diagonal from the top of one side to the bottom of the other, then take the opposite diagonal. If the two readings match within about 10mm, you're reasonably square. If they differ by much more than that, the opening is out of true.

This matters because a perfectly rectangular gate in a leaning opening will either jam on one corner or leave a wedge-shaped gap down the side. Tell the gate maker the diagonal difference and which way it leans. They can often adjust the frame or advise on packing, and it's far cheaper to solve at the drawing stage than on your driveway.

Allow for Posts, Hinges and Latch Clearance

This is the part that catches most people out. The gate's width is not the size of the opening.

• Posts: if new posts go inside the opening, subtract their combined thickness. Around 100mm square is typical for lighter gates, 150mm square for heavy hardwood or framed driveway gates.
• Hinges: allow roughly 10 to 20mm between gate frame and post, depending on the hinge type. Adjustable hinges give a little slack; bolt-through or weld-on fittings give you almost none.
• Latch and meeting gap: on double gates, leave 10 to 15mm where the leaves meet, and check the latch or drop bolt has room to work.
• Ground clearance: plan on 25 to 50mm, and more on sloping or loose surfaces.

A useful rule of thumb: opening width minus posts minus 30 to 40mm of total clearance gives you a sensible maximum gate width. When in doubt, order slightly under rather than over. A gate with a 15mm gap can be packed out; a gate that's 15mm too wide cannot.

Recording Everything Before You Order

Bring it all together on one page so nothing gets lost between the driveway and the order form.

• Width at top, middle and bottom, plus the narrowest figure.
• Height at each side and centre, with the reference point clearly noted.
• Both diagonal measurements and the difference between them.
• Whether posts are included, their size, and whether they sit inside or outside the opening.
• Ground surface, slope direction and the direction the gate will swing.
• Any obstructions — downpipes, meter boxes, kerbs, planting, drains.

Then, if you can, measure it all a second time on a different day with a fresh eye. An extra ten minutes with a tape and a notebook is the cheapest part of the whole project, and it's the part that decides whether your gate still swings freely in twenty years' time.