Considerations for Building a Floating Dock

With Summer and cabin season right around the corner, it might be time to start your next metal project: building a floating dock. In this article, we lay out a few planning steps to consider before and during construction of your floating dock.

What Metal Should Be Used to Build the Dock Frame?

Deciding what type of wood, metal or polymer you want on your dock’s walking surface is important aesthetically. But structurally, another important decision is what type of metal to use for the frame. Since it will be placed in contact with water, it should be a corrosion-resistant metal.

It is recommended that a marine grade aluminum be used to construct the frame. 5XXX series or 6XXX series aluminum is recommended for marine service. Stainless steel could also be used, but it could be quite expensive, so it is only recommended if the environment demands it (e.g. high strength requirements, chlorine-rich surrounding).

You definitely want to avoid plain carbon steel unless it has a special coating, such as being galvanized. However, even galvanized steel is not ideal as it can be dangerous to weld. It also must be re-galvanized if welded or cut, which can be difficult for a hobbyist. Even if properly coated or galvanized, damage or degradation of a coating over time can still cause plain carbon steel to corrode in a marine environment, so it is not an ideal material to use.

Do Welds for a Dock Need to be Airtight?

Since the dock will be partially submerged in water (certain parts are completely submerged), do the welds being made for the dock need to be airtight? While it depends on the application, for most residential docks the answer is no. While it is encouraged that the welds on the dock frame be made with the highest possible quality, airtightness is generally not a requirement for the frame.

Airtightness would be a concern if the flotation components are made of metal and being welded, but most docks use materials other than metal for their flotation devices. Common examples of this include plastic drums or other hollow shapes made from a polymer. These polymer flotation devices are held in place by the welded metal frame, and the welds on the metal frame do not need to be airtight for them to still do their job.

How Do I Anchor My Floating Dock?

Without some sort of anchoring device, all your hard work building your floating dock could literally float away. Depending on the type of dock, anchoring can come in several forms. The most common anchoring technique is using metal poles and brackets.

Aluminum brackets are fastened or welded to the frame. The brackets have a round collar on the end that is not attached to the frame. This collar is placed overtop of an aluminum pole that is driven deep into the earth beneath the water. The pole should be quite a bit higher than where the top of the frame is floating (roughly 50-100 cm) to accommodate for waves and changes in water level. The collar is slightly loose fitting, allowing the bracket and the frame to move vertically along the length of the pole while still keeping the floating dock from moving laterally. This pole and bracket anchoring combination should be done throughout the dock. As a rough guideline, the poles should be spaced every few feet and for every pole placed there should be one placed symmetrically on the other side of the dock.

While there are many other items to think through when building a metal dock, such as length, shape, and budget, these are a few of the most important. With the proper material selection for the frame, quality fabrication practices, and adequate anchoring, building a floating metal dock is well within reach.