Replacing Fence Posts in Sydney: Repair or Replace?

Most fences in Sydney do not fail all at once. The palings or sheets are still sound, the rails are straight, and then one post starts to move. Push on it and the whole bay rocks. That is almost always where a fence's life ends - at ground level, in the posts - and it is where the repair-or-replace decision actually gets made.

How to tell it is the post, not the fence

Walk the line and push firmly near the top of each post in turn. A post that flexes a little and springs back is generally doing its job. One that moves at the base, taking the ground or the footing with it, has lost its grip and is not going to recover.

In timber, decay happens at and just below the ground line, where the post is both wet and exposed to air. The timber a hand-span higher can look perfect, and the end buried in concrete can still be sound, while a band in between has gone soft. Push a screwdriver into that zone: if it sinks in instead of biting, the post is finished, whatever the rest of it looks like. How quickly that happens depends a great deal on the timber and the treatment used, which is covered in our comparison of hardwood and treated pine for fencing.

In Colorbond-style and other steel posts, the equivalent failure is corrosion at the base - very often hidden by soil, mulch or a garden bed that has crept up against the post over the years. The post looks clean at eye level and has rusted through where nobody has looked.

Why bracket and spur repairs sometimes work, and often do not

The repair kits sold at hardware stores - drive-in anchors, mending plates, concrete spurs - are not a con. They work when the post above the damage is still structurally sound and the fence hanging off it is light enough for a splint to carry. They fail when the post is soft through a long section, when the footing has moved rather than the post having broken, or when a gate or a tall solid panel is loading that post. A splint fixed to timber that is soft for a few hundred millimetres will move again, and by then you have paid twice. If you are weighing up a patch against proper work, our guide to repairing a damaged fence sets out what is genuinely repairable, and our fence repairs service page explains how we approach it.

One post, a section, or the whole run

Posts along a boundary are usually the same age, the same material and in the same ground. If one has gone, the rest are on the same clock. That is the real question behind a post replacement: not whether this post can be replaced, but how many more are close behind it.

Replacing a single post on a fence that is otherwise sound is good value and worth doing. Replacing the third post in two years on the same run usually is not - at that point the money is better spent on the fence rather than on holding it up. Our guide to when a fence is worth replacing and our notes on how long a timber fence lasts both go into that call in more detail, and the main fencing page covers the full range of work we do either way.

The old footing is the part people underestimate

Pulling the post out is the easy half. Underneath it there is usually a concrete footing, and that footing has to come out too if the new post is going back in the same position - which it generally has to, because the rails and panels are set to it. Getting it out without wrecking the bays either side takes some care, and the lump of concrete and spoil then has to go somewhere. On a narrow Sydney site with no side access and no room for a barrow, that logistics problem can be a bigger part of the job than the carpentry.

Timber and steel posts come out differently

On a timber paling fence, the palings and rails on the affected bays can normally be taken off, the post replaced, and the same material put back, provided the palings are not themselves brittle. Expect some breakage on an older fence - old palings do not always survive being unscrewed.

On Colorbond-style fencing, the posts are slotted and the sheets sit inside them, so a post in the middle of a run cannot simply be lifted out. The sheets either side have to be released first, which means the work spreads further along the fence than the single failed post suggests, and the sheets need to be handled carefully if they are going back in.

Gate posts are usually the first to go

A gate post does a different job from a fence post: it carries a swinging weight, takes a shove every time someone goes through, and gets wet at the base more often because the ground there is disturbed. A few millimetres of movement in a gate post reads as a dropped, dragging gate, which is why so many gate problems turn out to be post problems. We have written separately about fixing a sagging timber gate, including how to tell the difference between tired hardware and a post that has let go.

If the posts are on a shared boundary

Posts failing along a dividing fence is a shared-fence conversation before it is a repair job, because the fence between two properties is generally the responsibility of both owners. The process for that in New South Wales, including how notices work and what happens if you cannot agree, is set out by NSW Fair Trading, and we have covered the practical side in our guide to who pays for a dividing fence in NSW. It is worth having that conversation before the work starts rather than after.

What we look at on site

On a post job we check every post rather than just the one you have called about, look at the ground line and whether soil or garden beds have built up against the posts, work out whether the footings have moved or the posts themselves have failed, assess the condition of the rails and fixings that will have to come off and go back, and find out where the old concrete and spoil can physically go. Those five things decide whether the honest answer is one post, a section, or a new fence - and we would rather say so up front. If cost is the main question, our guide to what drives fencing costs in Sydney explains what moves the number.

Frequently asked questions

Can you replace one post without taking the whole fence down?

Usually, yes. On a timber fence the work is normally confined to the bays either side of the post. On Colorbond-style fencing it spreads a little further because the sheets have to be released from the slotted posts, but it is still a localised job rather than a rebuild.

My posts are concrete. Can those be replaced?

They can, though the method is different and the old footing is generally harder to remove. Concrete posts tend to fail at the base or at a crack rather than rotting, and a cracked post that is still carrying a fence is not something to leave alone.

The post is leaning but it is not rotten. Is that still a post job?

Often it is a ground problem rather than a post problem. A sound post that leans has usually had its footing undercut by water, had soil built up or cut away on one side, or is being pushed by roots or a raised garden bed next to it. Resetting a sound post is a different and generally smaller piece of work than replacing a failed one - but the cause needs addressing, or it will lean again.

Is it worth replacing posts on a fence I plan to replace anyway?

If the new fence is a long way off and the current one is unsafe or likely to come down in the next decent blow, a post replacement buys you that time safely. If a new fence is close, the money is usually better held for it. We will tell you which of those two situations we think you are in.

Where the whole run is coming out rather than a few posts, the job changes shape again. Old fence removal and disposal in Sydney covers removing a full boundary fence, the old footings and where the different materials end up.

Retaining wall sleepers fail in much the same pattern, from the bottom up - our guide to concrete versus timber sleepers explains when sleepers can be swapped and when the posts are the real problem.

The same principle applies to decks, where the joists and bearers do the work the boards get the credit for. Our guide to deck repairs in Sydney covers how to tell which part has actually failed.

If posts along your fence are moving, rotting at the base or rusting out of sight, we can look at it and tell you honestly whether it is a post, a section or the fence. We work across Sydney - the Sutherland Shire, St George, the Inner West, the Eastern Suburbs, Canterbury-Bankstown and the surrounding areas. Get in touch for a quote and we will come and have a proper look.