Start underneath, not on top
Nearly every dock repair call starts the same way: a board has gone soft, or the whole walkway feels springy. The temptation is to pull the bad boards, put new ones down and move on. On a structure in brackish tidal water that is often the wrong move, because the decking is rarely the first thing to fail.
Pressure-treated decking sits in the sun, dries out between tides and is replaceable in minutes. The joists under it stay damp, sit closer to the splash zone and hold water in every joint and fastener hole. Marine borers work from inside the timber outward, so a joist can be structurally finished while still looking solid from three feet away. The useful inspection is the one done from below, at low tide, with something to probe with.
What fails, and in what order
Fasteners go first. Salt air and wet-dry cycling attack hardware harder than timber. Under-specified nails and bolts loosen, corrode and lose their hold. A dock that creaks and moves under foot is frequently a hardware problem rather than a timber problem.
Framing goes next, usually at connections — where a joist meets a stringer, where a stringer is bolted to a pile, anywhere water can sit.
Pilings last the longest but fail the most expensively. A pile rots at the waterline, is eaten below it, or loses embedment when the bottom scours out around it. Replacing one is real work: a new pile driven alongside, load transferred across, the old one cut out and removed.
Decking is usually the symptom, not the disease.
After a storm
Northeast Florida gets storm surge, and surge does particular things to docks. It lifts decking off the frame from underneath, because the water pushes up before it pushes sideways. It racks framing out of square. It scours the bottom around pilings and reduces their grip without anything looking wrong from the bank.
If your dock has been through a surge event, the things worth checking are whether the decking is still fastened down at every point, whether the structure is still square, whether any pile now stands at a slightly different angle, and whether the bottom around the pilings is noticeably deeper than it was. A dock can look entirely normal and have lost a meaningful share of its capacity.
When we will tell you not to repair
We would rather turn down a repair than take money for work that will not last. If the pilings have gone, if more than about a third of the framing needs replacing, or if the structure has moved as a whole, repair money is being spent on a foundation that cannot support it. In that case the honest recommendation is dock replacement, and we will show you the arithmetic rather than just assert it.