Your Quick Guide To Finding the Floating Dock Builder That’s Right For You

Floating docks also known as floating marinas are buoyant on the water, built using encapsulated foam flotation affixed to a frame structure. Floating boat docks remain at a constant height i.e. independent of the river or lake level fluctuations and generally protected from the wave motion making them adaptable to most types of waterway environments. There are differences in the engineering and design of small private floating docks vs larger commercial installations. Here we’ll address the commercial applications for floating docks. There are some helpful things to know before deciding on a floating boat dock builder for your waterfront area.

What is The Best Type of Floating Dock?

There are many factors to consider in choosing the best type of floating dock. Depth of water, measure of water level change, exposure to wind and waves, budget, time, and resources that you can invest in maintenance, the material used, the life of the dock, etc. are some of the prime factors that help in determining what suits your business, your location and your customers.

What Type of Structure is Used for Floating Docks?

Floating boat docks typically have four main components for the structures used in the floating dock industry: the framing or support structure, flotation, decking, roofing and anchoring:


Some dock manufacturers offer multiple framing options. Others have found one to be the best fit for their customers.

Galvanized steel truss
A properly designed and engineered galvanized steel truss system is the most popular in freshwater locations. Its layout flexibility, strength, ease of assembly, repairability and long life are strong advantages.

Wood structures are aesthetically pleasing, but wood exposed to water and weather over time can deteriorate more rapidly than other materials and become a more costly option due to maintenance and replacement. Wood framing should be used in more protected and less fluctuating water environments. Saltwater has a less corrosive effect on wood than metals, but requires special treatment against the elements.

Corrosion-resistant aluminum will last against the elements, but the required gauge to support the demands on the structure make it a more costly option.

Pre-stressed concrete is formed to house the dock flotation. Designs employ waler beams to connect and support the modular concrete dock sections, or they can be bolted together. Concrete properly designed, installed and maintained can be a long lasting, functional option. Makers invest millions in plant and manufacturing facilities to produce concrete docks, which are popular solutions for saltwater environments.

Galvanized steel
For durability, longevity and flexibility, galvanize metal truss frames are functional and economical solution for all freshwater floating marina systems. The right engineered design of the truss is the most important aspect of this solution. All environmental factors must be considered to insure strength and long life. Like concrete, galvanized metal framing is created in modules bolted together and easily rearranged as needed for repair or expansion. Flotation is securely attached to the frame and also easily replaced if necessary. Properly designed, constructed and galvanized, these frames can last up to 60 years.


In the early days, floating boat dock builders used sealed steel drums for flotation, similar to a pontoon. In the late 1950s and early 1960s, expanded polystyrene blocks replaced the metal drums. Today, most floating boat docks use expanded polystyrene flotation in various forms.

Exposed (open) polystyrene blocks
Uniformly sized blocks are molded and attached under the wood or metal structures as flotation. Exposed polystyrene is more vulnerable to the elements, fuels, impact and saturation over time, but may be a low cost alternative to more lasting applications. Because it is almost always white, wear, grime and algae are more visible.

Encased polystyrene
Polystyrene that is expanded into molded polyethylene cases is currently the most popular floating dock flotation among dock builders, marina operators, and owners. It provides uniformity and structural strength; ease of replacement or relocation; resistance to fuels, aquatic life and impact; and longer life. Because the color is usually black, it provides a uniform, clean appearance for many years.

Concreted-encased flotation
This type of flotation is most simply described as a precast, prestressed concrete shell with an inner core of expanded polystyrene. These floats are manufactured at the dock builder’s plant, then delivered and assembled on-site using various systems of metal pipes, bolts and cables. The offer stable but more costly dock construction. While impervious to fuels, weather and aquatic life, they can be cracked by heavy impact, but will not lose buoyancy. The concreted encasement can also serve as the deck.


The most common options for floating dock decking are concrete panels, pressure treated wood and composite wood-look decking.

  • Treated Wood: Wood decking dates back to the original fixed boat docks used centuries ago. Today’s treated wood offers a classic wood look that is much more durable. It can last up to 20 years subject to annual maintenance. It requires regular or alternate water sealing to keep the water from saturating the wood. But eventually, wood deck panels will need replacement.
  • Composite Dock Material: Composite decking panels have the look of real wood, and are also popular for outdoor residential decks and stairs. They are often advertised as maintenance-free, but in the elements, nothing is maintenance-free. These synthetic composite materials generally hold up well and have a good lifespan with minimal maintenance. Higher traffic areas can experience a shorter lifespan.
  • Molded concrete panels: A variety of patterns, surfaces and colors are possible with concrete panels. Similar to swimming pool decking, the concrete can be colored and cast to provide a cooler touch for bare feet. The surface can be brushed, smooth or patterned


Boat slips can be open, meaning no roof, or covered. Roofing should be engineered and designed to specific aesthetic and environmental requirements dictated by location, dock structure, boat and slip sizes, dock design and local laws.

Corrugated metal roofing is the most popular and practical option for floating boat docks. It offers light weight, strength, stability, long life and aesthetically uniform appearance. Varying roof heights can accommodate large and small boat sizes.

How long Do Boat Docks Last?

The life span of boat decks depends upon the type of dock, the material used, etc. Floating docks can last up to 20-75 years while stationary docks can last around 25 to 35 years.

How Much Does It Cost To Build A Floating Dock?

The cost of building a dock depends on many factors, including the location, number, types and sizes of slips; type of structure used, groundwork, permits required, etc. Each floating dock builder has their own system for quoting a dock installation.

How Should I Select the Right Dock Builder?

Your selection should be based on some important factors. All floating marina builders are not the same. The one you choose should offer the following:

  • Experience
    Often individuals will launch a new dock building company after having worked for another builder. Be careful. They may offer what sounds like a great price, but will they be there for you when you need them. You need a expert. A company with a proven track record over many years.
  • Reputation
    The best dock builders can provide many good references to vouch for their work. Ask for them.
  • Resources
    Does the company have the material, capacity and personnel to do what they say they will do, now and in the future
  • Product
    The finished product should not only meet your current goals, but also your future needs. These qualities include proven engineering solutions, beauty, strength, stability, expandability, repairability and value.
  • Dependability
    Will the dock builder stand behind their product and support their customer for years to come?

MDI has a 60-plus year reputation for engineering excellence, product superiority and unsurpassed customer service. Our “On time, on budget. Guaranteed.” Promise is one we have upheld from our beginning as pioneers in the marina industry. Let’s discuss your plans and see if we can help you with them.

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