Wood, Concrete, Steel or Composite Pilings: What to Specify
By Ed Brannigan, Marine contractor. Reviewed by Dana Whitcombe, technical reviewer.
Pile Driving & Piling Repair | Boat Lift Installation Back in '94, I was driving 14-inch treated pine on a private dock in Fernandina Beach. The inspector walks up carrying a spec that said 'prestressed concrete, 16-inch square, 60-foot.' We'd already set eight sticks. That's how a lot of jobs go: the paper catches up to the tide. Thirty years on Gulf and Atlantic coasts taught me there's no universal answer. Wood, concrete, steel, composite — each one earns its spot under the right load, water, and budget. The question isn't 'which is the best piling.' It's 'which is the best piling for this cove, this soil, and this owner.'
Wood Pilings: The Old Standard
Treated southern yellow pine is what I grew up with. At twenty, I was setting fifteen-foot tail piles on Gulf beach houses, and we were done by lunch. A good SYP pile is straight, denser than people think, and about a third the weight of concrete. It needles and it squeaks when it drives, but you can feel it in the hammer. In freshwater and brackish water it'll outlive the owner more often than not. Old cypress used to be the spec, and I've seen cypress stumps still holding a dock in Georgia after sixty years. But you can't get cypress in grade anymore, not in quantity. The catch is saltwater marine borers. And the treatment matters more than the species. AWPA covers this in UC4B and UC4C, and those numbers matter. I specify ACQ or CA-B for private work; the quality depends on the plant, and that's the thing. A lot of that pine comes through Koppers plants, and I ask for the treatment certificate before it leaves the yard. A sloppy treatment charge can leave you with timber that worms love. For a 45-foot pile in a soft river bottom, give or take, I expect it to carry 30 tons in good sand. Maybe half that in mud. If the spec calls for saltwater and a long service life, I start looking at concrete.
Concrete Pilings: Heavy and Hard
Concrete is the workhorse when you need a heavy vertical load and a stiff deck. The ones I see most are prestressed square piles: 16-inch, 18-inch, or 24-inch. A 16-inch square is usually good for 100 to 150 tons axial, depending on length and soil. It's made in a plant with steam-cured strands, 270-grade, and 5,000 to 6,000 psi concrete. That's something you cannot generate on site, and the quality is consistent if the plant is honest. The big advantage in saltwater is that the prestressing compresses the concrete, so cracks stay hairline if they appear at all. That means chloride doesn't hit the strand as fast. Ordinary steel will corrode when it's exposed; a concrete pile just sits there with a pH over 12. But it's brittle. If the hammer is undersized or the cushion is wrong, you'll drive a crack through the head and never know until the pile starts rusting from the inside. One digression: I once saw a 24-inch concrete pile come off the truck with a horizontal crack ten feet from the tip. The crane had picked it with a spreader bar that was two feet short. The owner's inspector flagged it because another guy knew to look. That's a real thing: production crews will tell you it's fine, but a cracked prestressed pile is then a different animal. It won't break if you're lucky, but 'lucky' isn't a spec.
Steel and Composite: The Change-ups
Steel piles are what you need when wood and concrete won't drive, or when you have to design a batter pile that takes big lateral loads in a hurricane. HP shapes and closed-toe pipe piles can take a beating. I've driven HP 14x73 through dense sand and coral around Miami. They are not cheap, and they rot in the splash zone if you don't coat them or give them cathodic protection. In clean sand you might see 1/16 inch of corrosion in 50 years. In a marina with old fill and low oxygen, the same pile disappears on you. That water eats steel faster than people expect. Composite piling is the new kid on the block. I've used HDPE fender piles on a small marina fascia, and they're great for bump and bounce. Fiberglass reinforced polymer piling can carry real load, but it costs like a new truck and still has connection details that make me nervous. Composites are worth it where you need no corrosion and no marine borers. For a full dock foundation, I want to see a dynamic test before I believe the catalog.
Wood vs Concrete: How to Spec It
Here's the honest split. For a single-family dock in a high-tide river with soft mud and no hurricanes, wood is the sensible spec. You can drive it with a small excavator-mounted hammer, you can cut it with a saw, and if a boat hits it, the pile splinters but still takes the hit. A wood dock with a few braces will be decent for twenty-five to thirty years. You'll replace a couple of piles, but that's a maintenance job, not a salvage event. Concrete pays off when you're building something that cannot settle. A ferry slip, a fuel dock, a pier with a crane. A prestressed concrete pile does not bounce when the wharf deck works. It also handles high compressive loads with fewer piles, which can save you time on the water. Wood vs concrete pilings is not a one-size-fits-all; it's a load-per-dollar question. Pricing usually runs per linear foot plus delivery and crane time. A wood pile is cheaper per foot, no question. But I've seen jobs where two concrete piles replace four wood piles, and the per-foot price misleads. If the pile count drops from six to two, the labor and schedule can flip the comparison.
Don't Forget the Hammer and the Soils
Too many specs start with a pile and ignore what drives it. I've seen a big diesel hammer, call it 160,000 ft-lb, turn a small concrete pile into a Popsicle. You need a hammer energy that matches the pile weight and the soil resistance. That means a soil boring, not a guess. And if a pile foundation bid comes in crazy low, ask what they didn't drive. Finally, put quality control in the spec. Have the precaster certify the concrete, and have the driving contractor log blow counts. A crooked pile is a warranty problem; a cracked pile is a liability. Don't trust the plant, don't trust the hammer, don't trust the inspector. Verify. That's the one thing I've learned in thirty years.
Frequently Asked Questions
Are wood pilings still used in saltwater? Yes, if you specify the right treatment. AWPA UC4B or UC4C covers marine exposure. In tropical waters with heavy borer attack, concrete or steel is usually a better bet. How long do concrete pilings last? In good prestressed concrete with no major cracking, 50 to 75 years is a reasonable number. I've seen concrete piles outlast the dock they supported. Which is cheaper, wood or concrete pilings? Wood is cheaper per foot and cheaper to drive. But if soil conditions require long piles or heavy loads, concrete can be cheaper per ton of capacity. Compare the installed pile, not the sticker. Can I mix wood and concrete pilings on the same dock? Yes, but be careful. Concrete piles are much stiffer, so they'll attract more load and wood piles can slacken over time. Design the stiffness into the system, otherwise keep them in separate bents.