Dock Decking Materials Compared: Wood, Composite and Aluminum

By Ed Brannigan, Marine contractor. Reviewed by Dana Whitcombe, technical reviewer.

Dock & Pier Repair | Boat Lift Installation Last spring I spent a morning in Biloxi tearing up a ten-year-old wood dock that a homeowner had just paid to have "refreshed." The top boards looked fine from the driveway, but the fastener heads were rusted to nubs and the stringers had dry rot where water had pooled. I've built and repaired docks on the Gulf and Atlantic for thirty years. Wood, composite, aluminum—I've installed all three on everything from a twelve-foot kayak launch to a two-hundred-slip marina. And the honest truth is there's no single "best" material. It's a trade-off between upfront cost, lifespan, maintenance, and what you can live with. Here's a straight comparison to help you decide. I'll give you the good, the bad, and the ugly, and I'll tell you where I'd put my own money.

Pressure-Treated Wood: The Workhorse

Most residential docks are pressure-treated southern yellow pine. It's cheap, it's easy to cut, and every contractor knows how to work it. For the decking alone, you're looking at maybe half the material cost of composite, and in some cases a third. But that's just the ticket price. Lifespan? In saltwater, think ten to fifteen years. Freshwater might stretch it to twenty, give or take. Modern treatments like ACQ and Copper Azole do a better job than the old CCA, but the wood still checks, warps, and splinters. And the fasteners are the weak link—I've seen stainless screws pull out of soft, waterlogged stringers when the decking outlives the structure. You've got to seal it every couple of years, or it grays out and cracks. But if you use a sealant that traps moisture, you'll speed up the rot. There's a reason I tell people wood is "inexpensive now, costlier later." If you're on a budget and you're willing to keep up with it, it's fine. Just don't expect it to be the last dock you'll ever buy.

Composite: The Low-Maintenance Promise

Then there's composite decking—brands like Trex, Fiberon, and the capped stuff from TimberTech. The big selling point is no painting, no sealing, no splinters. And that's partly true. You'll never have to stain it. But you will have to wash it. The last composite dock I pulled out—twenty-year-old uncapped boards—was still structurally solid, but it had black mold in the grain and a surface slicker than a wet tile with algae on it. We pressure-washed it and it still looked like a decade of swamp. Capped composite is better; it has a plastic shell that resists moisture and staining. But it costs more, and it loves to expand and contract. In July in the South, that stuff can move a quarter-inch over a sixteen-foot board. You have to leave the right gaps and use hidden fasteners that let it slide. And the "zero maintenance" claim is marketing, not reality. You'll still need to sweep off leaves, rinse off bird droppings, and watch for mold in the shade. Figure two to three times the material cost of treated pine. If you hate staining, it's worth considering. Just don't treat it like a miracle.

Aluminum: The Marine-Grade Option

Now, aluminum is what I'd choose for a commercial dock or a house that sits in the path of every hurricane that comes across the Atlantic. Extruded aluminum decking—like you get from ShoreMaster or AlumiDock—is light, rot-proof, and it doesn't feed termites. It’s also incredibly durable in salt air. I've seen aluminum docks that were still working after thirty years. But it's not all sunshine. You'll pay more up front than wood or composite. You need a carbide blade to cut it, and you have to use stainless steel fasteners or you'll set up galvanic corrosion that eats through the aluminum in a few seasons. It also gets hot. In the middle of a July afternoon, a barefoot step on an unpainted aluminum plank will make you yelp. Most manufacturers powder-coat it, which helps, but if you choose a dark color, you're in trouble. Installation is faster and lighter than it sounds. But every brand has its own clip or screw system. And you need to think about the rest of the dock—aluminum decking on a wooden frame doesn't always play nice. The expansion rates are different and the fasteners want to work loose. Aluminum shines when the whole structure—stringers, frame, all of it—is built to match.

The Part Everyone Screws Up: Fasteners and Structure

Here's the hard truth: the decking is only as good as what's under it. You can spend thousands on high-end boards and still have a wobbly, rotten dock if your stringers and fasteners are wrong. For treated wood, use hot-dipped galvanized or stainless steel screws. Not electrogalvanized—that's just a light rinse and it'll rust in one season. For composite, most brands require their own concealed clips, which are often stainless. For aluminum, stainless is non-negotiable, but you also need to avoid bimetallic corrosion where the screw touches the aluminum. Basically, do your homework. And don't ignore spacing. Composite boards need gaps for expansion. Wood needs room to swell. Aluminum has specific requirements based on the section weight. If you jam boards together, they'll buckle or pop. If you space them too wide, you'll catch a heel. I've seen contractors skip the joist tape and then spend a fortune fixing rot on the stringers. A good dock is a system, and the structure carries the load. The decking is just the face.

My Call After 30 Years

So what would I do on my own dock? Depends on the plant, as my old foreman used to say. If I had a saltwater place with a budget, I'd go with capped composite. It's not perfect, but it gives you the best balance of cost, looks, and a decade of low-maintenance service. I'd use a light gray or tan color to keep the heat down, and I'd plan on washing it twice a spring. If I were building for a marina or a commercial operation, I'd go aluminum. It's the most reliable in a storm, and when downtime costs money, you don't want to be patching boards. And for a simple freshwater dock on a cabin budget? Pressure-treated pine, stainless screws, and a plan to replace the top someday. That's the honest trade-off. No material is the answer to everything. There's no free lunch in the marine environment. Ask your contractor what he'd put on his own dock, then ask him why. If he gives you a straight answer, you've got the right guy.

Frequently Asked Questions

Which dock decking is cheapest over the long run? Pressure-treated wood is cheapest up front. But when you figure in sealant, replacement, and labor, a capped composite can even out over 20 years. Aluminum costs the most up front, but with no staining or rotting, it can last 30 or more. Is composite decking slippery when wet? Yes, especially in saltwater where algae grows. Capped composite with a brushed or grooved surface is better, but you still need to clean it. Aluminum with non-skid is least slippery when clean, but it can get oily. Can I use regular lumber screws on a pressure-treated wood dock? No. Use hot-dipped galvanized or stainless steel. Regular steel screws rust out in a couple of seasons, and then you're pulling out heads and fixing damage. Does aluminum decking heat up in the sun? It can. In a summer afternoon, bare feet will know it. Powder-coated aluminum in a light color helps, but if you want barefoot-friendly, composite or wood is more forgiving.