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How to Make a Styrofoam Floating Dock

Peggy Epstein

Lot of materials are available for building docks, but none feature the buoyancy and ease of use as Styrofoam billets. One square foot of Styrofoam is enough to keep 55 pounds afloat. Styrofoam is made up of thousands of air chambers that act together to create an unparalleled floatation devise.


If you do not wish to use treated wood, use a wood such as cedar or redwood that is resistant to decay and insects. If you are going to attach ladders or grab bars, use aluminum or stainless steel.


Get some good strong help; this is not a one person job.

Docks floated on 55-gallon drums can not only develop leaks, but are unstable and can rock excessively with the wind and waves. Styrofoam will never leak and is completely free of the pounding noises made by hollow drums.

  1. Build the frame for your dock according to your plan using pressure-treated lumber. For the purposes of this article we will be building an eight-foot square dock, but you can adapt the directions to fit any size you desire.

  2. Turn your dock over so the bottom side is facing up.

  3. Measure the inside distance from side to side of the dock and cut your Styrofoam billets to that length with your hand saw. The under-side should be ten inches deep to hold the Styrofoam billet.

  4. Cut the Styrofoam to fit snugly inside the bottom of the dock’s frame. An eight-foot square dock will take four billets.

  5. Place a 1x4-inchx8-foot piece of pressure treated wood lengthwise over the first billet.

  6. Secure the Styrofoam billet by drilling holes through the 1x4 Styrofoam and frame. Bolt snugly together.

  7. Repeat step 6 with the remaining Styrofoam billets until all four are in place and return your dock frame to its upright position.

  8. Install the dock’s floor by nailing down 2x6-inch boards perpendicular to the direction of the Styrofoam billets.

  9. Attach chains and anchors to the underside of the dock and place the anchors on the dock’s deck. Push the dock into the water and sink the anchors when you have the dock in its desired location.