The most cost effective way to build a dock and boathouse is with a barge. This is the case not only for island properties. Even on the mainland shores, bringing the materials via barge to the project is significantly more efficient than having the materials delivered by truck and then carried by hand, often down significant slopes, to the dock. In some cases the beams are to too large to even carry. The barge is loaded up at the closest boat launch by crane and stays at the dock as the workers build the boathouse. Important to load the materials you need first at the top! The barge is also used as a working platform. We own our barges and this allows us to leave them at the projects. It costs well over $100/hour to rent a barge so your boathouse construction costs will increase significantly if your builder is reliant on others to get the materials to your shoreline.
See our website home page