A floating dock can be useful year round, but is especially fun place in summer to hang out, swim, or launch boats. I tried to keep this instructable simple using mostly just a drill and no cutting. Okay, technically more than one tool since you will need to check square using a tape measure, but really just one power tool (the drill) and you can do it all!
Special shout out to Pilx who inspired this build with his awesome floating dock. Our variation of this uses 2x6's rather than 2x8's and 2x4's and has a different cross bracing method. We also used different decking, but that is entirely optional. Plix also used eye screws to attach the ropes while we simply drilled holes through our 2x6's and attached that way.
Step 1: Find the Parts
The materials you will need
4ea food safe, water tight poly barrels, these are often left over from various food manufacturing and can often be found cheaply on Craigslist
7ea 8' Pressure treated or cedar 2x6's
2ea 8' pressure treated or cedar 2x4's
Suitable decking material, could be cedar or in this case 18ea 8' composite decking boards AND appropriate exterior grade fastening screws
50' of rope suitable for water contact
4ea corner brackets (we used galvanized L brackets but this step is optional)
exterior grade screws for attaching boards, I used approx 75ea 3" #8 screws
A small amount of caulk to seal barrels
Step 2: Layout
Layout 4 ea of the pressure treated 2x6's, measure from corner to corner to make sure they are square and screw these together through the ends with about an inch of overlap on the inside corner. I also added some small corner brackets on the inside of these joints but I have a tendency to over build projects and I'm not sure this was necessary.
Step 3: Barrel Placement
Place your second row of 2x6 using a barrel as a marker. Barrels come on many different sizes so I can't give you an exact measurement for this, but the barrel should fit snug with a small space between the barrel and the ground. For my dock this meant about 17 1/2" on center. Screw boards into place using 2 screws through the end of each board.
I also took a moment to add some caulk around the barrel openings. This is probably not necessary, but I wanted to make double sure that no water leaked in.
Step 4: Continue Placement
Place the rest of the barrels appropriately in each corner and screw the cross sections in place using the same method. There should be enough space remaining at this point to attach the last 3 remaining 2x6's approx 16" on center across the remainder of the opening. Attach each end using 2 exterior grade screws.
Step 5: Securing With Rope and Turning Over
At this point I cut my 50' rope into 4 pieces and drilled pilot holes approx in the middle of the boards where they meet the barrels and tied on the barrels using a truckers hitch. This will keep the barrels in place in rough water. You will probably want a friend to help you flip it over at this time since its kind of heavy.
Step 6: Cross Bracing
I actually cut some cedar 2x4's at this point to add some additional bracing to the barrels. But in hind sight I realized that these were the only cuts I made for the project and it would have been better to just use uncut 2x4 going all the way across the bottoms of the deck as shown in the black and white drawing. My method here worked fine but adding whole boards would have given better cross bracing AND this would have truly been a one power tool project. We use a lot of recycled materials so sometimes we have to stretch our usage.
Pro Tip: Notice how close I am to the water? That will make launching this thing later a lot easier.
Step 7: Decking
Secure your decking material across the tops of your supports. You want to make sure you are located close to the edge of your body of water since its going to start getting pretty heavy at this point. I chose composite decking because it not only lasts long and is low maintenance, but it was on sale! You could also use 5/8" or 2 by cedar decking and that would work great.
Step 8: Enjoy!
There are various ways to use a floating dock, in our case we made a hinged section which sits on top of our floating dock and is also attached to our stationary dock. We also mounted various cleats for boating and might possibly add a swim ladder at some point in the future.