If you live on the water, a floating dock is a logical extension of your home's external structures. As docking space for your boat, it will rise and fall with the tide while providing an interesting exterior space for guests. It also expands your serviceable yard space into the water. Since the dock floats, selecting the correct amount of flotation is a key factor in building a floating dock. Construction can be accomplished on land, much like boat-building, and provides the excuse for a "launching party" for friends.
Commercially available floats filled with materials such as expanded polystyrene foam (EPS) or syntactic foam provide more efficient flotation than air-filled floats. Syntactic foam and EPS have similar flotation characteristics and are available in various sizes capable of supporting between 450 and 4,754 pounds. Generally, floats should be positioned where you would place support posts if the floating dock were a deck in your yard, rather than a floating extension of your yard.
The dock is just like any other outdoor decking and can be any shape or size that pleases you. Remember, though, that the primary purpose is as a dock. It will have to have bollards or cleats on the water side to which boats can be secured.
Using cleats (available from any boating store or outlet) provides the most flexibility for docking, since they can be installed anywhere along the perimeter of the floating dock.
Mooring the Dock
A floating dock must be moored to the land lest it simply float away. The best mooring for the dock will be to two bollards---thick poles set into concrete in the ground, like the supports for a deck. On the deck itself, cleats attached to the end nearest the shore are tied to the bollards. The choices for mooring lines to hold the dock include nylon line, which stretches and can absorb shocks; polypropylene line, which floats, but will burst rather than stretch; and chain. Position the dock and moor the dock to the bollards.