Dock Flotation Calculations

It’s imperative that your floating dock is able to support a sufficient weight and can effectively keep afloat whatever design you have. A small, traditional dock pier may only need a few floats mounted to the ends and middle. More likely, however, you may need many more depending on the size and design of your dock.

Before installing a floating dock or adding more flotation to an existing wood- or aluminum-framed dock, spend some time running a few calculations so you know how many dock floats to get in order to create a safe and sturdy floating dock.

How to Calculate Dock Flotation Requirements

To start, you’ll want to calculate the total square footage of your dock. A typical residential dock float will support roughly 30 pounds per square foot. Larger marinas that experience more traffic should estimate 40 pounds per square foot when running dock flotation calculations.

For example, a standard 4’x10’ dock is 40 square feet. 40 square feet x 30 pounds per square foot = 1,200. That means you need 1,200 pounds of flotation to accommodate the dock design.

Next, you need to assess buoyancy. Our 2’x4’x12” Formex float is tank tested to support 446 pounds in freshwater. In running your calculations, you should always round up. For a 4’x10’ dock then, you would need a minimum of 3 floats of this size to adequately support the dock weight (1,200 / 446 = 2.7).

When running the numbers, you should also account for the weight of your decking as well. A lightweight dock frame and aluminum decking require less flotation support it.

Lastly, you need to decide which size float you want to use. In terms of height, most residential docks use 12” tall floats. Our 2’x4’x12” Formex float offers the versatility to meet most, if not all, dock designs. These polyflange dock floats consist of a solid block of expanded polystyrene foam, which is encased in a plastic shell and made of high molecular weight high-density polyethylene.

The Formex float can be added to dock sections that are 8 to 12 feet wide (and wider) to provide additional flotation. They can easily be attached to an existing wood or metal dock or used with a new dock construction.

To learn more about the specific dock hardware and flotation needs you should have for your dock design, contact us at RDS Dock Hardware to ask your questions.