There are a number of factors to ask before you figure flotation requirements. If it is a homeowner’s dock with a couple of people, we use about 30# per square foot to calculate flotation. A marina with more people needs about 35# per square foot. It isn’t easy to get this exact number but you can come close. The lower the dock is to the water, the more stable it will be. The more footprint in the water (the amount of surface water covered by floats) the more stable it will be.
Next, you should figure the height of the float. We have 12”, 16”, 20” and 24” high floats in most models. The lower the float, generally the more stable the dock will be. The example is a homeowners dock 6’ wide and 20’ long. The amount of square feet of dock is first determined by multiplying 6’ x 20’ = 120 square feet. We then use 30 pounds per square feet and multiplying 30 x 120 = 3600 pounds of flotation needed. Next figure out what size float you would like to use.
We will show two examples:
1. A large float (FC-4612) 4’ x 6’ x 12” floats 1390# each. Divide 3600# by 1390# = 2.58 floats – 3 would be needed.
2. A small float (FC-2412) 2’ x 4’ x 12” would be a good choice it floats 450# each. Divide 3600# by 450# = 8 floats. For a commercial application, do the same calculation except use 35# per square foot. Keep in mind, that these are rough calculations. The dock weight, material, decking, and etc. will affect the actual amount of flotation you need.