If you are thinking of building a residential dock this summer, one of the first questions to figure out is how many floats are needed for a floating dock.
Generally speaking, 3-6 per floats are needed per residential dock section. This amount can differ dependent on the size of your dock, the dead + live weight, and the free board desired.
In this article we will be going in depth of what you will need to begin your DIY Journey.
Note: For this entire article, we will be discussing residential docks specifically.
In this Article:
Sizing your Dock
The great thing about DIY projects like a floating dock is the flexibility to make it your very own. The biggest constraint we see with floating docks in terms of sizing is budget.
Lumber can very quickly drive up the price of dock when considering the framing, cross members, stringers and decking that is required to complete a floating dock. If price is a concern, I suggest checking out aluminum floating docks, if you are not in an area where water freezes over winter.
Once a budget has been set out, sizing your own DIY dock becomes easy. Most docks consist of two parts: the walkway and the platform.
Walkway & Platform Sections
If you went with aluminum floating docks, the sizing of each section is pre-determined, and you can move on to the next step. For wooden floating docks, you generally want one or two walkway sections, and one platform section.
Again, this is completely up to you, and we recommend checking out different examples for inspiration.
Walkways are the piece of the dock that is anchored to land & extensions, A.K.A the entrance to your dock. We generally recommend sizing these in the same width as floats are long. We go into further detail in the "Placing your Floats" section of this article.
For quick reference, this measurement is usually 4', 5', 6', or 8' as that is the standard length of our floats. As for the length of your walkway, it will depend on how far out into the lake you are wanting to go. This can be one or more sections, with the most common recommended being one or two 20 ft. sections, attached together with outside male/female corner brackets. One section will be semi-floating, and the second fully floating.
The length of each section is defendant on the length of a single lumber piece, as this ensures stability within each section.
Platforms are the main area of a dock where lawn chairs, ladders, safety cleats and other accessories are kept. On-boarding of PWCs and smaller boats also happen here.
Generally, these are much larger and heavier than walkway sections, which ultimately will affect how many and what size of floats you will require, so keep that in mind. Sizing varies completely on your preference, but keep in mind the larger the platform the more reinforcement is needed for the extra weight.
For reference, our most common platform size is 10' by 20' which is also shown as an example in the "Placing your Floats" section of this article.
Custom Wooden Dock Shapes
So far, we have only talked about rectangular shaped docks. This is for good reason.
An important note for new builders is the importance of symmetry. Keeping your walkway & platform sections either rectangular or square in shape will greatly simplify the process of figuring out how many floats you need for your floating dock.
Additionally, supporting the weight evenly across the entire platform becomes tricky with custom shapes. If this is your goal, we strongly recommend employing a professional to design your dock.
Once you have your walkways & platforms sized up, it is time to figure out the dead & live weight of your dock.
Dead Weight vs Live Weight
The most important part of a floating dock is keeping it afloat. We do this by calculating the weight of each section of the dock.
Dead weight refers to the weight of the dock and all permanent fixtures. This includes but is not limited to floats, lumber, hardware, decking, dock side & corner edging, ladders, safety cleats, etc.
Live weight refers to the variable factors of weight such as people, gear and any other accessories that may go on top of the dock structure.
The dead weight added with the live weight is the total weight we will be using for our calculating buoyancy section.
IMPORTANT NOTE: These calculations are done per section, not the entire dock.
Walkway sections do not usually bear as much live weight as platforms, but this is incredibly important to keep in mind if transporting heavy gear across the walkway sections.
Calculating Buoyancy
Again, before continuing on to this section, it is crucial to understand the dead & live weight per section of your dock.
Calculating Buoyancy requirements can be tricky as to begin, you need to add in the weight of the floats to the entire section, before you even know which floats you need.
The easiest way narrow down which floats are appropriate are by looking at your section sizing.
You want to spread the buoyancy capabilities evenly throughout the entire section. Again we will be separating walkways from platforms as the float positioning will be slightly different.
Walkways
For walkways, if you followed our sizing guidance, the width should be the exact same as our floats i.e. 4', 5', 6' or 8' if you are using our floats. It's easiest if all your floats you use per section are the same size, so keep that in mind.
As an example, we will be using the max size of walkway we recommend; an 8' wide, 20' long walkway.
Two floats are minimum, one at each end of the walkway. Three or more is recommended to ensure even support in the middle of the walkway.
From our example, we have 20' of length to evenly distribute buoyancy across. This platform design is more than wide enough to accommodate for multiple floats outside of the two mandatory floats. Next step is to figure out which we need.
There are three separate float sizes we commonly stock that are 8' (96") in length: the 2' (3 options), 3' (4 options) & 4' (5 options) wide series.
If we take the largest width (4') to reduce installation time, and choose the shortest float for cost savings (12"), we come to the float size of 48" width, 98" length, & 12" height with a buoyancy rating (from our website) of 1,834 lbs. per float. Between all three floats, this walkway section can support a maximum of ~5502 lbs. With that, each float weighs 110 lbs, for a total of 330 lbs of flotation.
In total, these three floats can support ~5172 of total (dead + live) weight, with the floats being fully submerged.
IMPORTANT NOTE: Our buoyancy ratings are calculated with the float fully submerged, meaning your lumber would be touching the water & total height above water will be the height of your lumber + height of your decking. Please read our "Freeboard Desired" section to learn why this rating is only for reference and should not be used as a final calculation.
Platforms
Platforms are a similar concept as walkways, with much more flexibility in terms of the float you choose.
For almost all platforms, 6 floats are recommended.
If you have a much larger platform (larger than 10' x 20') we recommend contacting a professional as this platform will be incredibly heavy and requires more floats spread out evenly through out the entire platform.
The 6 floats should be spread out 4 in each corner and 2 in between length wise. Check out the "Placing your Floats" for an example.
Since platforms almost always require 6 floats, we have a standard float we recommend: our 48" (4') x 60" (5') series floats, that can be installed length or width wise, depending on the placement of your cross members & stringers.
All that is left for buoyancy calculation is to determine the height required, again for this example we will be using the shortest float we offer, 12". For 6 floats of 48" width x 60" length x 12" height sizing, your total buoyancy rating (fully submerged) is 7140 lbs. and all together the floats weigh 378 lbs.
The maximum weight this configuration can hold is 6762 lbs.
IMPORTANT NOTE: Our buoyancy ratings are calculated with the float fully submerged, meaning your lumber would be touching the water & total height above water will be the height of your frame + height of your decking. Please read our "Freeboard Desired" section to learn why this rating is only for reference and should not be used as a final calculation.
To wrap this section up, the sizing/design of your dock will heavily impact the float choice. When creating your design, its a good rule of thumb to include 3 floats for walkways and 6 floats for platform designs. For simplicity, we are assuming the floats are under full load, A.K.A fully submerged.
Freeboard Desired
Moving on to our last section, freeboard.
Freeboard refers to the vertical distance between the water level and the top of the dock, including framing and decking.
The first thing to go over, dock floats are not designed to be fully submerged. This rating is in place for reference only. Using the calculations above without freeboard considerations will create an incredibly unstable dock.
We wrote this part last as desired freeboard can be subjective, and overall can cause confusion if you begin calculating this aspect along side the length & width of each float. We are going to be using the same two examples as above, now focusing on freeboard or in simpler terms, the height of a dock's deck above the water.
Walkways
Lets look back at our above example. We have an 8' x 20' walkway, with 3 floats attached, that have sizing of 48" width, 98" length, & 12" height and are evenly spaced out.
Total buoyancy rating after taking away the weight of the three floats, is 5172 lbs. fully submerged.
Like we mentioned earlier, the floats in this configuration can not effectively handle this weight or heavier. So what weight rating does it truly have?
This is where the subjective aspect of freeboard comes in. "Low-profile" docks are very popular amongst docks that often have people on & off boarding in canoes or kayaks.
If you are new and don't see a need for a shallow freeboard, we recommend 12-14 inches of freeboard for most residential applications. This ensures stability and extra room if you need to load the dock with un-expected heavy items.
Remember the height of the frame and decking is included in this measurement. The float will itself will have a height above water of about 8" in this example.
With that in mind, our 12" height float from our example would have to be ~67% above water to reach the above water float height measurement of 8". Therefore, the float could only sink ~33% to reach the desired freeboard.
Taking this to our previous buoyancy calculation of 5172 lbs. we see that the effective weight rating for this float configuration is actually only 1724 lbs. of total (dead + live) weight.
If you require more buoyancy, all you would need to change from here is the height of the float, which won't impact your design plans. You would then do the same calculations as above to ensure you have enough buoyancy at the desired freeboard.
Platforms
Using the same method, lets check out the effective weight rating for our 10' x 20' platform. This configuration has 6 floats, measuring 48" width x 60" length x 12" height.
Total effective buoyancy rating for this platform is 6762 lbs. after taking the weight of the floats into account. Again, this rating is calculated at full submersion of our floats.
If we assume we want the same desired freeboard of 8" (12" total with framing and decking), we can find out the effective rating of this floating dock configuration is ~2231 lbs.
If we wanted to increase this rating, we would increase the height of the float.
Placing your Floats
Next, we wanted to give you some design examples and where to place your dock floats once you have done all your calculations.
For walkways, the width of the walkway should be the same as the length of the float. If you are using our dock floats, the width options are 4', 5', 6' or 8' wide walkways.
Once the width is figured out, next making sure the floats are spread out evenly through the walkway ensures stability and constant buoyancy ratings across the entire design. For this example, we will be using our widest walkway design, an 8'x 20' model.
Just to emphasize one last time, the width of the walkway should be the same as the length of the float.
Similar to the platform designs, the size of float can change depending on weight of your treated lumber, decking used, live-weight variants, and the free-board desired.
In general, for platforms, floats should cover the perimeter of the platform as best as possible. For this example, we will be using our 10' x 20' platform design.
Keep in mind the sizing of the floats can change depending on the weight of your treated lumber, decking used, live-weight variants, and the free-board desired.
For almost all platforms, we recommend using a 6 float configuration like the one shown above. If you are going bigger, we would recommend talking to an expert to build your platform section. Float placement is very important to ensure proper and even buoyancy ratings across the entire platform.
Free Floating Dock Plans
As you can tell, there are a variety of aspects that need to be considered when building your own floating DIY dock.
If you are looking for quick and easy plans, we have free plans on our website, for both walkway and platforms that you can use to base your dock design from. Click on "Part #/ Model" to view them.