16x16 Floating Dock Using 55-Gallon Barrels
Step-by-step guide made from Indy Farm Life's YouTube video.
Build a sturdy 16-foot by 16-foot floating dock for a pond or lake. This project uses pressure-treated lumber for the frame, composite decking for a maintenance-free surface, and twenty 55-gallon plastic barrels for flotation.
- Difficulty: intermediate
- Finished size: 16 ft x 16 ft
Safety
- Always use appropriate personal protective equipment (PPE), including safety glasses and gloves, when cutting and handling pressure-treated lumber.
- Exercise extreme caution when working with heavy equipment like tractors to move the dock frame.
- Be careful when working near and in the water, especially during the launching process.
Must know before you build
- Round barrels prevent ice crushing; dock floats up or pushes out of ice.
- Seal all PT lumber cut ends with water sealer to prevent premature rot.
- Trex composite decking needs 16" on-center joist spacing; 24" causes flex.
- Seal barrels on a cool day; hot-day sealing causes collapse as temps drop.
- 16x16 dock weighs thousands; plan heavy equipment like two tractors for launch.
- Dark composite decking gets extremely hot; lighter colors prevent bare foot burns.
Tools
- Tractor with loader (tractor with front-end loader, John Deere) (optional)
- Circular saw
- Cordless drill/driver
- Ratchet straps (27 foot) (optional)
- Tape measure
- Hammer (framing hammer)
- Bar clamps (bar clamp) (optional)
- Sledgehammer (optional)
- Paintbrush
- Caulk gun
Materials
- 55-gallon plastic drums (20, plastic drums, 55-gallon)
- Pressure-treated lumber (dimensional lumber, 2x12)
- Pressure-treated lumber (dimensional lumber, 2x10)
- Composite decking boards (composite decking, Trex)
- Pressure-treated post (6x6)
- Water sealer (1, Thompson's, 1 Gallon)
- Lag screws (1/2 in x 5 in)
- Joist hangers
- PVC Primer (1, purple PVC primer, Oatey, 8 oz)
- PVC Cement (1, Oatey, 8 oz)
- Silicone Caulk (DAP, 100% Silicone)
- Hidden Deck Fasteners (hidden clip fastener system)
- Pressure-treated lumber (2x4)
- PVC Cleaner (Oatey)
- 16 penny nails
- Shims
Step by step
Step 1: Cut and Assemble the Outer Frame
The 2x12 perimeter boards and 6x6 corner blocks are cut to size. The cut ends are sealed with a water sealer before the 16'x16' outer frame is assembled using lag screws.
- Cut Frame Lumber and Corner Blocks. Cut the 2x12 boards for the outer frame and the 6x6 post into corner blocks. Two of the 2x12s should be cut to 16 feet, and the other two should be cut 3 inches shorter to accommodate the thickness of the adjoining boards.
- Tip: A tractor with a grapple or forks can serve as a convenient, mobile workbench for cutting long, heavy boards.
- Seal Cut Ends. Apply a water sealer, like Thompson's WaterSeal, to all the freshly cut ends of the pressure-treated lumber to prevent water from wicking into the wood.
- Assemble the Outer Frame. Lay out the 2x12 boards to form the 16'x16' perimeter. Place the 6x6 blocks in the corners for reinforcement. Clamp the corners together, pre-drill holes, and secure them with 1/2" x 5" lag screws.
- Tip: After assembling the frame, measure the diagonals to make sure they are the same distance. This confirms the frame is square.
Step 2: Install Joists and Blocking
The 2x10 joists are installed using joist hangers, spaced 24 inches on center. Cross-blocking is then added between the joists to create a rigid grid structure for the dock.
- Install Joists. Install the 2x10 joists inside the frame using joist hangers. Space the joists to leave a 22-inch opening between them to snugly fit the 23-inch diameter barrels. (22.5 inches (24 inches on center) might be too loose)
- Tip: If your long runs are a little warped and the joists are not sitting quite tight, use a long ratchet strap to draw things up before securing them.
- Common mistake: The 24-inch on-center spacing may be too wide for some composite decking, which often specifies 16 inches. Check your decking manufacturer's recommendations.
- Install Cross-Blocking. Cut and install 2x10 blocking pieces between the joists. This creates a grid pattern that adds significant rigidity to the frame and defines the bays for the barrels.
Step 3: Prepare and Seal the Barrels
To ensure the barrels are completely watertight, the bungs (caps) are removed, and the threads are treated with PVC primer and then PVC cement before being tightened. A final layer of silicone caulk is applied for extra security.
- Seal Barrel Bungs. Remove the bungs from each barrel. Apply PVC primer to the threads of both the bung and the barrel opening, followed by PVC cement. Screw the bungs back in tightly. For extra waterproofing, apply a bead of 100% silicone caulk around the sealed bung.
- Tip: Set up an assembly line to efficiently seal all the barrels at once.
- Common mistake: PVC cement does not bond with polyethylene (the material of the barrels), so this step relies on the glue filling the threads and the existing gasket. A marine-grade sealant like 3M 4200 might be a more reliable alternative.
Step 4: Install Barrel Supports
2x4 boards are cut and installed between the joists. These act as cross-braces or 'gussets' that create a cradle to prevent the round barrels from slipping through the frame openings.
- Cut and Install 2x4 Barrel Supports. Cut pieces of 2x4 lumber to fit snugly between the joists within the barrel bays. Screw these supports into place to create a cradle that will hold the barrels and prevent them from falling through the frame.
- Tip: Position the barrels so the 2x4 supports catch the end without a ring. That narrower end can slip through the frame opening, especially if the barrel has collapsed slightly from temperature changes. The ringed end is wider and naturally stays in place.
Step 5: Launch the Dock Frame
The heavy dock frame is lifted using two tractors. The sealed barrels are then slid underneath into their designated bays, and the entire assembly is carefully pushed into the pond.
- Position Barrels and Lift Frame. Move the sealed barrels to the dock site. Using two tractors with loaders, carefully lift the entire dock frame.
- Insert Barrels and Launch. While the frame is lifted, slide the barrels underneath into the bays created by the joists and blocking. Once all barrels are in place, carefully push the dock assembly into the water until it is fully floating.
Step 6: Install Composite Decking
With the dock floating, the composite deck boards are laid out and attached. A temporary bridge is made with a trailer to easily access the dock. The boards are installed using a hidden fastener system for a clean, screw-free surface.
- Create a Work Platform. Back a utility trailer up to the floating dock frame to create a stable bridge and work platform. Tie the dock to the trailer to keep it from floating away while you work.
- Install the First Deck Board. Lay the first composite deck board along one edge of the frame. Secure it using starter clips that screw into the side of the frame and fit into the groove of the board.
- Install Subsequent Deck Boards. For the remaining boards, place hidden T-clip fasteners into the groove of the installed board over each joist. Slide the next board into place, ensuring the clips engage in its groove. Drive the provided screws through the clips into the joists to secure the boards.
- Tip: Lay out all the deck boards on the frame first to create a full walking surface, which makes the installation process safer and easier.
- Tip: Use a towel or knee pads to kneel on, as the dark composite decking gets very hot in the sun.
- Tip: Don't tighten the fastener screws all the way at first. Let them float so you can slide the next board into the clips, then cinch the screws down tight.