Boat dock and marina construction field guide

What dock construction is, and why it is the hardest place to build

A dock or a marina is a structure built in the water, and the water is the harshest place a contractor ever works. Everything on land that lasts thirty years lasts a fraction of that at the waterline. Steel corrodes, wood rots and feeds marine borers, ice grips a piling and lifts it, and waves, boat wake, and current pound the structure from every direction at once. Then you add electricity. The moment shore power reaches a powered dock, you have created the risk of electric shock drowning, where alternating current leaking into the water paralyzes a swimmer who then cannot swim and drowns.

So two things govern every decision on a dock. The water makes everything harder, and the electricity makes it deadly. Build for the water by choosing fixed or floating to suit the level, founding the structure on proper pilings or encapsulated floats, and using marine-grade lumber, composite, and fasteners that survive immersion. Treat the marina electrical as a life-safety system under NEC Article 555, with ground-fault protection and bonding, not as ordinary site power. And understand that none of it is legal until the waterfront permits are in hand.

This guide covers the dock types, the foundations, the materials, the electrical, the gangway, anchoring, and the permitting that wraps all of it. The structural design, the electrical, and the permits each belong to a qualified party, the engineer, a marine-qualified electrician, and the permitting agencies, not to a rule of thumb. For the screw-in foundations that often carry these structures, see the helical pier and screw pile guide. For the shoreline grading and the legal outlet behind the bulkhead, see the drainage and grading guide.

Why the water makes it harder and the electricity makes it deadly

Hold both framings in your head at once, because they pull the design in different directions. The water attacks the materials and loads the structure. Salt and moisture corrode every metal, the wet-dry cycle and fungi rot the wood, gribbles and shipworms bore into untreated timber, ice heaves the pilings in cold country, and the combined push of wave, wake, current, and wind tries to move or break the whole thing. That is a materials-and-structure problem, and it is solved with marine-grade materials, corrosion-rated hardware, and an engineer who sizes the structure for the real loads.

The electricity is a different kind of problem, because it does not damage the dock. It kills people. Alternating current that leaks from faulty boat wiring or dock wiring into the surrounding water can pass through a swimmer's body and paralyze the muscles. The current is often too small to be felt and leaves no visible sign on the water, yet it is enough to stop a person from swimming. They go under and drown a few feet from a ladder. This is electric shock drowning, and it is the deadliest hazard on any powered dock.

The mistake is treating one framing and ignoring the other. A beautifully engineered dock with sloppy electrical can still kill a child. A perfectly wired dock built of the wrong steel rusts into the lake. Both have to be right, and the electrical, because the failure mode is death rather than a callback, is where you hedge hardest to NEC 555, the AHJ, and a qualified marine electrician.

What is electric shock drowning?

Electric shock drowning, ESD, is death by drowning that happens when alternating current leaking into the water passes through a swimmer and paralyzes the muscles, so the person cannot swim and goes under. It is the single most dangerous hazard at a powered dock, and the worst part is how quiet it is. There is usually no shock you can see, no spark, no sound. A swimmer simply loses the ability to move and drowns, often within reach of help.

The current usually comes from a fault on a boat or on the dock, not from the obvious bare wire. A frayed conductor, a wiring error, or a damaged grounding system can put current into the water when a battery charger, a water heater, an air conditioner, or even a light switch cycles on. The level needed to paralyze muscles is far below what trips a standard breaker and often below what a person feels. ESD is most documented in fresh and brackish water, where the body conducts current more readily than the surrounding water, but the safe assumption is that any powered dock can be lethal.

Three defenses matter, and all belong to a qualified marine electrician working to NEC Article 555 and the adopted code: ground-fault protection that opens at a low leakage threshold, equipotential bonding that ties the metal together so a fault cannot build a voltage difference in the water, and listed marine equipment installed correctly. The blunt operational rule that closes the gap the wiring cannot is simple. No swimming in, on, or near a marina or a powered dock. Post it, mean it, and de-energize the dock before anyone is allowed in the water.

NEC Article 555: the marina electrical as a life-safety system

Marina and dock electrical lives under NEC Article 555, Marinas, Boatyards, Floating Buildings, and Docking Facilities, and it is written to do one job above all others: keep leakage current out of the water so ESD does not happen. Read it that way. The ground-fault protection in Article 555 is not there to protect equipment the way an ordinary breaker is. It is there to trip on the small leakage current that can kill a swimmer.

The shore-power pedestals are the visible piece, the posts at each slip with the receptacles, breakers, and metering. Recent editions of the code require ground-fault protection on those receptacles set to open at a low threshold, with feeder and branch protection set higher to coordinate, so a single boat's fault trips its own slip rather than the whole pier. The exact trip values, the 30 mA class on receptacles and the 100 mA class commonly cited on feeders, and the rules on leakage-current measurement where several boats share power, are set by the adopted edition. Confirm the numbers and the layout with the AHJ and a marine-qualified electrician, because the article has changed across recent cycles.

Equipotential bonding ties all the metal of the dock, the pilings, the ladders, the rails, the equipment, together and to the grounding system, so a fault cannot create a voltage gradient in the water around the structure. Use listed equipment rated for the wet, corrosive marine location, not ordinary site-grade gear. This is the part of the job to over-document and never value-engineer. The cost of getting it wrong is a body.

What is the difference between a fixed and a floating dock?

A fixed dock is built on pilings driven into the bottom, with the deck held at a set height above the water. A floating dock rides on flotation and rises and falls with the water level, held in position by piles or anchors. The choice is driven first by how much the water level moves. Where the level is stable, a fixed dock on pilings is simple and stiff. Where the level swings, with tide, with a reservoir drawdown, or with seasonal flooding, a floating dock that tracks the surface keeps a usable freeboard and a workable gangway all year.

Get this decision right before anything else, because it sets the foundation, the access, and much of the cost. A fixed dock in tidal water leaves you climbing a ladder at low tide and stepping off a submerged deck at high. A floating dock in shallow, stable water with a hard bottom is often more structure than the site needs. Match the type to the water, then design within it.

The table below is the starting frame. The site conditions, the design water levels, and the engineer's judgment decide the actual call.

The fixed dock

A fixed dock carries the deck on pilings driven or screwed into the bottom, with the framing and decking set at a chosen height above the high-water line. It is the right answer on water that holds a steady level, a lake with controlled elevation, a river reach without much swing, or protected water where the range from low to high is small. The structure is stiff. It does not move underfoot, it takes a boat lift and heavy gear well, and the pilings carry the load straight down into firm soil.

Deck height is the design decision that bites later. Set it for the highest water you will see, including storm surge and flood stage where they apply, plus freeboard, or the deck goes under and the planks float off. Set it too high and you are climbing to the boat in normal conditions. On water that swings more than a foot or two, the fixed dock stops working and the floating dock takes over. The pilings, their embedment, and the framing above all belong to the engineer, sized for the loads in a later section.

The floating dock

A floating dock sits on flotation and rises and falls with the water, so the deck stays the same height above the surface whatever the level does. That is its whole advantage. On tidal water, a reservoir that draws down, or any surface that swings through the season, the floating dock keeps a constant freeboard, the short distance from the water to the deck, so stepping aboard a boat is the same task at any level.

Freeboard is a real design number, not a guess. Too little and the deck wets and feels tippy under load. Too much and it rides like a wall and is hard to board from a low boat. The flotation is sized to carry the dead weight of the structure plus the live load of people and gear at the target freeboard. Because the dock moves, every connection has to tolerate motion: the gangway hinges at the shore end and rolls or slides at the dock end, and the dock is held in plan by guide piles or by an anchor and cable system covered later. The flotation itself is the next section, and modern rules govern what it can be made of.

The flotation

The flotation is what holds a floating dock up, and the modern standard is the encapsulated float: a closed-cell foam core sealed inside a thick polyethylene shell. The shell resists impact, sun, fuel, and abrasion, and because the buoyant core is sealed in, a punctured float keeps floating instead of sinking the dock. Encapsulated billets and foam-filled poly drums are the workhorses.

Bare foam is the thing to keep out of the water. An exposed expanded-polystyrene block under a dock breaks down under sun, wave, and boat impact, sheds polystyrene beads that pollute the shoreline, and soaks up water and fuel until it loses buoyancy and the dock lists. Loose-foam flotation is banned or restricted in many jurisdictions for exactly that reason, and several permitting agencies now require encapsulated flotation as a condition of approval. If a float is not encapsulated, assume it does not pass and confirm with the AHJ.

Size the buoyancy for the dead load plus the live load at the design freeboard, and watch the level the dock rides at over time. A dock that sits lower than it did when new is a float taking on water, and that is the early sign of a flotation failure before a section goes under. Distribute the floats so the dock rides level under uneven load, not just empty.

The pilings

The pilings are the foundation of a fixed dock and the anchors of a floating one, and they come two ways. Driven pilings, timber, concrete, or steel, are pushed or hammered into the bottom until they reach the embedment and bearing the engineer calls for. Helical pilings are steel shafts with helical plates that are turned into the bottom like a screw until the torque proves the capacity, which makes them workable from a small barge in tight water and useful where driving is impractical. For how helicals carry load and how installation torque correlates to capacity, see the helical pier and screw pile guide.

Embedment is everything. A piling that is not driven or screwed deep enough into firm material will not hold against the lateral loads, the wave and current pushing sideways and the ice pushing in cold country, and lateral load is usually what governs a dock piling, not the weight on top. The engineer sets the embedment, the size, and the spacing from the soil borings and the load case. In cold climates the same piling has to survive ice jacking, the next section, which adds an uplift load that a warm-water design never sees.

Match the piling material to the water and the design life. Timber needs the right marine treatment to resist borers, steel needs a corrosion allowance or coating and often a sacrificial detail, and concrete needs the right cover and mix for the exposure. None of that is a field call. It comes off the engineered drawings.

Ice jacking

Ice jacking is the cold-climate failure that ruins pilings, and it works by grip. Ice freezes around a piling, and as the water level rises, with snowmelt, rain, or a managed reservoir, the sheet of ice lifts and drags the piling up with it. The piling ratchets a little higher each cycle and does not come back down, so over a few winters the dock heaves out of alignment and the pilings stand proud of where they were driven. It is the same physics as frost heave on a foundation, applied to a post the ice has a death grip on.

The defenses are design and management. Drive the pilings deep enough that the soil holding them down beats the ice trying to pull them up, a number the engineer sets for the site. A smooth sleeve or jacket around the piling at the ice line can let the ice slide instead of grip. In a marina the common tool is a de-icer or a bubbler, a submerged unit that pushes warmer bottom water to the surface or pumps air to keep an ice-free ring around the pilings and the boats. Many cold-country docks sidestep the problem entirely by being floating systems that are pulled out or de-iced for the winter. If the water freezes, ice is a design load, not an afterthought.

The loads the structure has to survive

A dock is loaded from more directions than a building, and the engineer designs for the combination, not for each force alone. The live load is people and gear on the deck. The wind pushes on the structure and on the moored boats, which act like sails. Waves and boat wake slam the underside and the sides. Current drags steadily on everything in the water. Mooring and berthing add the pull of tied-up boats and the impact of one coming in. In cold country, ice adds both a crushing horizontal push and the uplift of ice jacking.

The point that catches people is that these loads stack and arrive together. The worst case is not the biggest wave or the strongest wind by itself, it is the realistic combination on a bad day, and a structure sized for the average condition fails on the day all of it shows up at once. Wind and snow loads reference ASCE 7, while the wave and current loading comes from a site-specific analysis of the water, and coastal flood zones add their own requirements. None of this is a rule of thumb. The marine structural engineer runs the load cases and sizes the pilings, the framing, and the connections, and the dock builder builds to that. Where the water gets rough, wave attenuation, a breakwater or a wave fence, becomes part of the design rather than an upgrade.

What materials hold up on a dock?

On a dock, ordinary building materials fail fast, so the framing and decking are marine-grade or composite, and the choice is driven by what the water does to each one. Pressure-treated lumber rated for ground and water contact, with a treatment and retention meant for immersion, resists the rot fungi and the marine borers, the shipworms and gribbles, that eat untreated wood at the waterline. Composite decking sheds the rot and borer problem and the maintenance that comes with wood, at a higher material cost, and it still rides on a treated or steel frame.

Borers are the wood failure people underestimate. In salt and brackish water they can hollow out an untreated timber piling from the inside in a few seasons, leaving a shell that looks fine until it snaps. The defense is the right marine treatment for the exposure, confirmed against the project's design life, not whatever treated stock the yard had on the truck.

Corrosion is the metal failure, and it is so central it gets its own section next. The short version: everything metal on a dock is either rated for the marine environment or it is a future failure. Pick the lumber treatment, the decking, and the hardware as a matched set for the water you are in, fresh, brackish, or salt, because salt is far more aggressive than fresh and the material that survives a freshwater lake will not survive a tidal bay.

Fasteners and corrosion

Fasteners and connectors are the number one material failure on a dock, because they are small, highly stressed, and surrounded by the most corrosive thing on site. Regular zinc-plated or bright steel hardware rusts out in months to a couple of years in the water, and when the fastener goes the connection goes, even if the lumber is fine. In salt and brackish water the standard is 316 stainless steel, the grade with molybdenum that resists chloride attack. Hot-dip galvanized is the practical minimum for freshwater service, but it degrades in salt within a few years, so it is not a saltwater answer.

Two traps put holes in good intentions. First, the copper-based preservatives in modern treated lumber are themselves corrosive to fasteners, so the hardware has to be rated for treated wood, hot-dip galvanized at minimum or stainless, never plain steel. Second is galvanic corrosion: put two dissimilar metals together in salt water and the less noble one becomes a sacrificial anode and eats itself. If the screws are 316 stainless, the joist hangers, bolts, and structural connectors have to be 316 stainless or compatible too. Mix stainless screws into galvanized hangers in salt water and you have built a battery that destroys one of them.

Specify the whole hardware package as one corrosion class for the water you are in, and write it on the drawings. The fastener is the cheapest part of the dock and the first thing that fails when somebody substitutes to save a few dollars.

The decking and the framing

The framing carries the deck and ties it to the foundation: stringers and joists in marine-treated lumber, steel, or aluminum, sized by the engineer for the live load and the marine load cases. The decking is the walking surface, marine-grade treated lumber or composite, and the details that matter are the gap and the slip. Leave a drainage gap between boards so water sheds and the deck does not trap a wet, slick film, and choose a surface with enough texture to walk on when it is wet, because a dock is wet by definition and a slick deck over cold water is a real fall hazard.

Fasten the decking with the corrosion-rated hardware from the previous section, and keep the connection details consistent so the inspector and the next crew can read the structure. The framing and the connections are engineered, not eyeballed, especially on a floating dock where every joint flexes with the motion and a connection that would last forever on land works itself loose over the water.

The gangway

The gangway is the ramp from the fixed shore or pier down to a floating dock, and it is the hardest accessibility detail on the whole job because its slope changes every time the water moves. At high water the gangway is nearly flat. At low water the same ramp gets steep. An accessible gangway has to meet the slope target under the design conditions, and the federal accessibility standards for recreational boating facilities set a target of 1:12, about 8.33 percent, with the practical relief that the gangway is not required to be longer than 80 ft to chase that slope on a fluctuating surface.

Three details make it work. The gangway hinges at the shore end so it can pivot as the float rises and falls, and it rolls or slides at the dock end so its length can take up the change without binding. A transition plate bridges the end of the gangway to the deck, and where that plate slopes more than 1:20 it needs a landing and the ramp details that go with it. Width, handrails, edge protection, and a slip-resistant surface round out the accessible design. Confirm the accessibility requirements that apply to the facility with the AHJ, because a private residential dock and a public marina are not held to the same standard, and the design water levels drive the geometry.

Anchoring the floating dock

A floating dock has to rise and fall freely and still stay put against wind, wake, and current, and there are two common ways to hold it. Guide piles are vertical piles the dock is captured to with rollers, brackets, or hoops, so the dock slides up and down the pile with the water but cannot drift away. This is the stiffer, more positive method and it shines where the level swings a lot, because the dock tracks the pile through the full range.

The other method is an anchor-and-cable, or chain, system: weights or embedded anchors on the bottom, connected to the dock by cables or chain with enough slack to let it rise to the highest water and enough tension to hold it against the loads. It suits deeper water or sites where driving guide piles is impractical, and it takes more design to get the scope and the tension right so the dock neither goes slack and wanders nor pulls tight and submerges at high water. Either way, the holding system is engineered for the same wind, wake, and current loads as the structure. A dock that breaks loose in a blow becomes a battering ram against every boat and dock downwind of it.

Do you need a permit to build a dock?

Yes. You cannot just build in the water. The waterfront is among the most heavily regulated places to build anything, and a dock almost always needs federal, state, and sometimes local approval before a single piling goes in. Building without it risks a stop-work order, fines, and an order to remove the structure at your own cost.

At the federal level, a structure in navigable water of the United States falls under Section 10 of the Rivers and Harbors Act, administered by the U.S. Army Corps of Engineers. If the work puts dredged or fill material into the water, including some kinds of bottom disturbance, Section 404 of the Clean Water Act applies as well, and that usually pulls in a state water-quality certification under Section 401. Many areas are covered by a general permit that speeds the approval of small residential docks, but coverage and conditions vary by district, so the Corps decides what applies, not the builder.

At the state level, the bottom you are building on is often public submerged land, and you typically need a lease, an easement, or authorization to occupy it, tied to the riparian or littoral rights that come with the upland property. State environmental agencies add their own review. The honest summary is that the permits are project-specific and stacked across agencies, and the way you avoid an expensive mistake is to confirm the full set with the Army Corps, the state, and the local AHJ before design is final, not after the barge is booked.

The environmental review

The environmental side of waterfront permitting is real work, not a formality, because a dock changes a living system. Decking shades the bottom, and the shaded strip loses the submerged aquatic vegetation that fish and shellfish depend on, which is why many permits limit deck width, require grating that lets light through, or set the height and orientation to reduce shading. Any dredging or filling stirs sediment and clouds the water, so a turbidity curtain to contain the plume is a common permit condition during construction.

Protected species and sensitive habitat can drive the whole design and the schedule. Seagrass beds, oyster reefs, spawning areas, and the presence of listed species can force the alignment to move, the work to pause for a seasonal window, or the method to change. The reviewing agencies set these conditions, and they are enforceable conditions of the permit, not suggestions. Plan the environmental controls and the in-water work windows into the schedule from the start, because finding out about a seasonal restriction after mobilization is how a project loses a season.

The installation

Building over water changes the logistics of every task. Material and crew reach the work by barge or from the shore end, and a pile driver or a helical drive head works off a barge or a crane with the water under it the whole time. The sequence usually runs foundation first, set the pilings or place the anchors, then build outward from shore so each new section is supported by the last, then assemble and float the deck sections for a floating system, then hang the gangway, then the electrical and the finishes.

Weather and water level run the schedule more than the calendar does. You drive pilings and set floats in workable water, not in a blow or a strong current, and on tidal water the level dictates when certain steps can even happen. A barge is a moving, unstable platform, and the margin for a dropped tool or a misstep is a person in the water, so the work plan accounts for the water level, the forecast, and the in-water work windows from the permit. Build the sequence around the water, because the water does not adjust to the schedule.

Safety on the water

The hazards on a dock job are different from land work, and two of them kill. The first is the water itself: a fall from a barge or an open deck, especially in cold water that saps strength and coordination in minutes, is a drowning risk. Personal flotation devices for anyone working over or near the water are not optional, and a means of self-rescue and a thrown line have to be within reach. Cold-water immersion shortens the time a person can help themselves to a matter of minutes, so the rescue plan is in place before the work starts.

The second is the electrical, and it has two faces. For the crew, lockout/tagout the dock power before working on it and verify it dead, the same discipline as any energized system. For everyone in the water, electric shock drowning is the standing hazard whenever the dock is powered, so no one swims near an energized marina or dock. Add the mechanical hazards of pile driving, the suspended hammer, the moving leads, the pinch points, and the unstable barge underfoot, and the dock job earns a real, water-specific safety plan rather than a land plan with a life jacket stapled on.

Maintenance

A dock lives in a system that is trying to take it apart, so maintenance is the difference between a structure that lasts its design life and one that fails early. The electrical comes first because it is the life-safety item. Test the ground-fault protection on the shore-power pedestals on a schedule, confirm the bonding is intact and not corroded through, and have the marina electrical inspected by a qualified party against NEC 555. A bonding connection eaten by corrosion has quietly removed the protection against ESD, and nothing on the surface shows it.

Then the structure. Check the pilings for corrosion, rot, borer damage, and movement, watching for ice-jacked pilings standing higher than they were set. Watch the floats for a dock riding lower than it used to, the early sign of a flooded float. Inspect the hardware and connectors for rust and for galvanic attack at any spot where metals meet, because the fastener fails before the lumber does. An annual marine inspection that covers the electrical, the foundation, the flotation, and the hardware catches the slow failures while they are still repairs and not replacements. For keeping a maintenance and inspection record that holds up over the life of the structure, the documentation section is next.

What to document

A dock outlives the memory of who built it and how, and the record is what answers the questions that come later: was the bonding ever right, what holds the floating dock in a storm, which permit conditions govern the next repair. Keep the permits, the engineered drawings, the electrical design and inspections, the piling and flotation specifications, and the inspection history together where the operator and the next contractor can find them. A field platform such as FieldOS keeps the photos, the inspection logs, and the as-built records tied to the structure instead of scattered across trucks and inboxes.

The table is the short list of what to capture and why it matters down the road.

The failures that show up on docks

The failures repeat across docks, and they sort into the deadly and the expensive. The deadly one is electrical: a dock with no NEC 555 ground-fault protection, missing or corroded bonding, and the electric shock drowning risk that comes with it. That is the one that ends in a fatality, and it is the one to chase first on any existing dock.

The expensive ones come from fighting the water and losing. Regular steel fasteners that rust out and drop connections. Exposed-foam flotation that breaks up, pollutes, and sinks a section. Pilings not designed for ice jacking that heave the dock out of line over a few winters. A gangway that is not accessible at the high-water condition. And the one that can erase the whole job: building without the waterfront permits, then facing fines and a removal order. None of these is bad luck. Each is a known mechanism with a known defense, and the defense is on the drawings before the work starts.

Common mistakes

• Ignoring electric shock drowning and skipping NEC 555 ground-fault protection and bonding on the marina electrical.
• Using regular steel or plated fasteners that rust out in the water instead of 316 stainless or hot-dip galvanized.
• Mixing dissimilar metals in salt water and setting up galvanic corrosion that eats the hardware.
• Specifying exposed-foam flotation that breaks up, sheds beads, soaks up water, and sinks a section.
• Driving pilings that are not designed for ice jacking, so the ice heaves them out over a few winters.
• Building without the Army Corps, state submerged-land, and environmental permits in hand.
• Designing a gangway that meets the slope at high water but becomes too steep and inaccessible at low water.

Field checklist

Standards and references

The electrical framework lives in NEC Article 555, Marinas, Boatyards, Floating Buildings, and Docking Facilities, part of NFPA 70, which sets the ground-fault protection, the bonding, and the listed-equipment requirements that exist to prevent electric shock drowning. Fire protection for marinas and boatyards is covered by NFPA 303, and the American Boat and Yacht Council, ABYC, publishes the marine electrical standards used for boats and shore power. The trip thresholds and bonding details have changed across recent code cycles, so confirm the exact requirements against the adopted edition and the AHJ, and have a marine-qualified electrician do the design.

The structure is the marine structural engineer's responsibility. Wind and snow loads reference ASCE 7, the wave and current loading comes from a site-specific analysis, and coastal flood-zone construction carries additional requirements. The pilings, the framing, the connections, and the anchoring are engineered to the combined load cases, not to a rule of thumb.

The permits are federal, state, and local. Structures in navigable water fall under Section 10 of the Rivers and Harbors Act through the U.S. Army Corps of Engineers, dredge-and-fill work falls under Section 404 of the Clean Water Act with a Section 401 state water-quality certification, and state agencies regulate the submerged land and the environmental review. Accessible gangways and boarding follow the federal accessibility standards for recreational boating facilities. The three things to hedge hardest, every time, are the electrical to NEC 555 and a qualified marine electrician, the structure and pilings to the engineer, and the permits to the Army Corps, the state, and the AHJ.

Units and terms

Dock work borrows vocabulary from foundations, marine trades, and the electrical code, so the same structure gets described in several languages across a drawing set, a permit, and an electrical inspection.

The terms below are the ones that carry the most weight on a dock job.

Fixed dock

A dock built on pilings with the deck at a set height above the water, suited to a stable water level

Floating dock

A dock that rides on flotation and rises and falls with the water, suited to tidal or fluctuating levels

Electric shock drowning (ESD)

Drowning caused when AC leakage into the water paralyzes a swimmer's muscles so they cannot swim; the deadly hazard at powered docks

NEC Article 555

The National Electrical Code article governing marina and dock electrical, written to keep leakage current out of the water

Equipotential bonding

Tying all the metal of the dock together and to ground so a fault cannot create a voltage difference in the water

Encapsulated flotation

A closed-cell foam core sealed in a polyethylene shell, which stays buoyant if punctured and does not shed foam; bare foam is restricted

Driven vs helical piling

Driven pilings are hammered into the bottom; helical pilings are screwed in until torque proves capacity

Ice jacking

Ice freezing around a piling and lifting it as the water rises, ratcheting the piling out of the ground over winters

Marine-grade fastener

Hardware rated for immersion, 316 stainless in salt water or hot-dip galvanized for fresh, matched to avoid galvanic attack

Gangway

The hinged ramp from shore to a floating dock, whose slope changes with the water level

Freeboard

The height of a floating dock's deck above the water surface, set by the buoyancy and the load

Waterfront permit

The federal, state, and local authorizations required to build in the water, including Army Corps and submerged-land approvals

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