What the parts are called, what the symptoms usually mean, and what to write down before you ring anybody.
Get a Quote →Most people who ring about a jetty start with an apology for not knowing what anything is called. It genuinely does not matter — “one corner has dropped” tells a contractor more than a part name would. This page runs the other way round: the symptom first, in the words people actually use, and the part name second so you have it if you want it.
The vertical posts driven into the lake bed. Owners usually say pylons; the trade says piles; they are the same thing. They carry everything. On a private jetty these are usually treated hardwood — H6 is the Australian hazard class for timber in marine waters — and they are the most expensive part to replace, so they are the part worth catching early.
The horizontal timbers spanning between piles that the deck sits on. Bearers run the long way and take the load to the piles; joists sit across them under the boards.
The boards you walk on. The most visible part and the cheapest to replace, which is why a jetty can look tired and still be structurally fine — or look freshly decked and be sitting on failing piles.
Diagonal members tying piles together so the structure resists sideways movement — wind across the lake, and the shove of a boat coming alongside.
Bolts, coach screws and brackets. In salt water these are consumable. The standard answer for marine work is grade 316 stainless, and it needs to be electrically isolated from any dissimilar metal it touches. Mixing metals is how good timber ends up held together by nothing: corrosion rates “can be greatly accelerated when two or more dissimilar metals are in contact with each other and exposed to a corrosive environment”. Ask whoever quotes what grade they are using and how the connections are isolated.
A floating deck held by guide piles, reached by a hinged gangway that rides up and down with the water. The floats underneath are either a sealed air chamber or a foam core inside a shell — both are in service. Either way, when one loses its buoyancy that corner sits low, and a corner sitting low is the thing to report.
Usually pile settlement — a pile sinking further into the bed than the others, taking that corner of the deck down with it. It is progressive, not sudden, so a small step in the deck is worth a look before it becomes a slope. How soft the bed is at your own frontage is a question for someone who has driven piles on that shore, not something to read off a map.
Bounce is a span problem, not a board problem. Either a joist under those boards has failed, or a bearer has, or a fixing has let go and the timber is no longer being carried where it was designed to be. Replacing the boards on top of a failed joist looks like a fix for about a season.
Sideways movement points at bracing or at the fixings holding it. A jetty is designed to be stiff against exactly that load, so movement that has appeared recently is a change worth reporting rather than living with.
That band is the splash zone, and it is where timber piles — pylons — fail first. Two things are eating them. Marine borers are the main one: shipworm, and the crustaceans that work the tidal band and leave a pile waisted like an hourglass. Wet-and-dry decay does the rest. The bridge inspectors' own guidance puts the worst of the borer damage between about 300 mm above and 600 mm below low tide, and warns that “while the interior of a pile may be practically eaten away, only a few small holes may be visible on the surface”. That is the point: a pile can look sound from the outside and be hollow. It is the reason poking at the timber with a screwdriver tells you more than looking at the deck does.
Where a jetty meets a rocky or rock-protected shoreline, movement in that rock is a foundation question rather than a timber one. What is actually happening varies by property, and it is not something to diagnose from a description or a photo alone — but it does change the job. A pile standing in disturbed ground is a different piece of work from the same pile in stable ground, and it is worth flagging to whoever quotes so the quote covers the real job.
Fixings at end of life. On its own this is the cheap end of the work. It matters because the timber it is holding may still be perfectly good, and because corroded fixings tend to be found alongside the reason they corroded — the wrong metal, or a coating that has been breached.
A float has taken on water. Sealed floats do not usually leak evenly, so a list is the first sign, and it gets worse rather than better. Guide piles and the gangway hinge are checked at the same time because a listing pontoon loads both unevenly.
Either the pontoon is no longer floating at the height it should, or the gangway hinge or rollers have worn or seized. Lake Macquarie’s tidal range is small — restricted by Swansea Channel, the lake’s only marine entrance — so a gangway that has started fouling at low tide has usually changed rather than been marginal all along.
The honest answer is that it turns on the piles. Decking, bracing and fixings are all replaceable in place, and a jetty on sound piles can be brought back a long way. Once multiple piles have gone in the splash zone or settled out of line, the arithmetic changes, because getting plant to the site is a large part of the cost either way and doing it twice is the expensive outcome.
That is a contractor’s call made on site, not a call to make from a website. What is worth knowing before the conversation is that “how many piles” is the question that decides it, and that a jetty which looks bad on top is often in better shape than one that looks fine.
Restricted tidal exchange through Swansea Channel means water sits longer against timber than it does in an open harbour. And a long wind fetch across a lake of 114 square kilometres loads bracing harder than the size of a private jetty suggests. How soft the bed is varies shore to shore, and that decides whether piles settle. A crew that works the lake knows which of those it is looking at before it gets out of the boat.
Five minutes with a phone saves a site visit, and it is what any contractor will ask for first:
Waterfront licence photographs have their own specification — whole frontage, high tide and low tide, from the water and from the land — and there is a right order to do the work and the photos in. That is set out on our Crown Lands waterfront licence page.
Tell us what you need and where the property is.