Build a Floating Home or Boathouse, What You Need

At HarborWare we get hundreds of calls throughout the week with questions about how to build a boat dock, particularly what size and quantity of dock floats are needed. Our more complicated answers are usually about floating homes and boathouses that are extraordinarily heavy.

First of all, we highly recommend consulting with a local licensed engineer familiar with boat docks to obtain a weight estimate of the structure. They have the ability to do this even if the structure isn't built yet. Second, you'll need to get necessary permits in place before breaking ground. Third, you want to pick the right size of dock floats and the right quantity. Floating homes and boathouses are usually a much bigger investment than a small lake house dock, so you'll want to do things right the first time!

Introduction to Dock Floats for Boat Docks

Dock Flotation (dock floats, float drums) can be defined as any device used in the construction of a boat dock that allows it to float on top of a body of water.

A floating dock will move up and down with water levels, contrary to a standing dock that is built on stilts which does not ever move. Most boat docks that are built on a water source connected to a dam are floating docks due to the effect dams have on water levels. When the dam opens up, water levels can drop several feet and if your boat dock is floating, it will lower down along with the water level.

In the mid-1900's, dock floats looked much different then how they look today. There were three primary types: styrofoam blocks, metal pontoons, and barrels. For many reasons, these primitive floating devices are now obsolete and are outlawed in most US states. Over the years styrofoam became hazardous to the environment, polluting lakes with small foam pieces that broke off little by little over time. Metal pontoons and barrels are hollow, so when punctured docks began to sink rapidly. Also, barrels that where once used to house chemicals were being re-purposed as dock flotation and started leaking deadly chemicals into our water source. Eventually the "encapsulated dock float" was developed and replaced all forms of dock flotation.

How to Build a Floating Boat Dock in under 60 Seconds

We often get asked "so, how do you build a boat dock anyways." This video is the quickest explanation, built primarily by children at a summer camp. All you need is dock floats, treated lumber, basic hardware and tools.

As you can see in the video, build a "box" frame using 2x6's. Then attach the float drums underneath using a 3" Lag Bolt and 2" Fender to hold the floats in place. Flip the dock over and attach your decking, which can be treated lumber, composite wood or plastic grated panels. Add your dock cleats, ladders and accessories and you're done!

How to Build Boat Docks with Dock Floats and Float Drums

Photo Source

Building your first floating boat dock is fairly self-explanatory for the most part. All you really need is a few basic tools and one or two of your brute friends. However the one thing that HarborWare's customers have the most questions about is the dock floats, how many they need and what size. Hopefully this page will answer all of the questions you may have.


How Many Dock Floats Do I Need?
Unless you're building a very small swim platform, you're going to need a minimum of 3 float drums: 1 for each dock-end and 1 in the middle (if you're building a straight floating pier for example). However, you may need 10 floats or even 50 if you're building something more complex like a U-Shaped boat slip or small neighborhood marina. On average we sell around 10 floats per small lake house dock. For marinas, it ranges from 24 to 240.


How Much Buoyancy Do I Need?
For a Residential Dock built with aluminum or wood frames, wood or plastic decking, and no roof: calculate your square footage, multiply it by 30 (estimating 30lbs. per sq/ft). You never want to estimate the rock-bottom, bare minimum buoyancy needed and have your floats completely submerged under water. They can run the risk of collecting water or moisture if this happens.

For a Heavy-Duty Residential Dock or Commercial Dock with steel frames, concrete decking and a roof: calculate your square footage, multiply it by 40 (estimating 40lbs. per sq/ft).

Residential 4'x40' Dock 4 x 40 = 160 160 x 30 = 4,800 estimating 30lbs pr/sqft

Commercial 4'x40' Dock 4 x 40 = 160 160 x 40 = 6,400 estimating 40lbs pr/sqft

What Size Dock Float Do I Need?

It depends on the width and length of your boat dock. Generally if your dock is 4' wide, you'll wan't a 4' float drum, whether the float drum is 4'x4'x16" or 2'x4'x16". In some cases it doesn't matter, such as if your dock is 20' wide by 20' long. Since we don't make a 20' float drum you can essentially use any size float on both ends as long as you're using adequate buoyancy.

As far as height, it's all a matter of preference. However most of the time Residential docks use 12" to 20" tall, while Commercial docks use 20" floats or taller.


What All Can I Build With Dock Floats?
Here is a list of all the things customers have used our float drums for:

• Boat Docks
• Boat Lifts
• Floating Boat Houses and Cabins
• Duck Blinds
• Oyster Farms and Hatcheries
• Industrial Agitators

How Much Is Shipping?
Most float drums must be shipped by freight truck and this can sometimes cost 25% of the total order. We suggest ordering at least 4 floats of any size because the cost to ship 1 or 2 is about the same as 4. Most sizes require freight truck shipping and they only ship by the pallet load.

Keep in mind we are the manufacturer, so even after shipping we're usually 20% less than a distributor's price, even if they claim to offer "free shipping." Also, we only have to charge sales takes in 4 states (AR, MO, OK, AL).

Why Can't I Use Foam Blocks or 55 Gallon Barrels Instead?
Unfortunately both are illegal in most states. The Environmental Protection Agency banned raw foam because overtime pieces break off and end up getting eaten by wildlife and polluting lakes. 55 gallon barrels were banned because they may have been previously used to store harmful chemicals. Getting caught using either one of these can result in hefty fines that are far greater than the cost of plastic encased dock flotation. On one lake we heard the fines were $1,000 per day.


Can you keep Dock Floats in Frozen Lakes?
Yes, but only if they're foam-filled. All HarborWare and Insul-Bead Corp dock floats we manufacture are foam-filled and are safe to keep in lakes and bays that freeze over in the winter. “Tests have shown that when foam-filled drums are left in the water over winter, the ice forming along their bottoms is thinner than ice surrounding the float. The insulating qualities of the foam are credited with preventing the ice from forming. Together, the greater strength and lesser ice buildup seem to give foam-filled drums an advantage for icebound floating docks.”  – The Dock Manual by Max Burns, Page 33, Published January 4, 1999

If you have major ice shifting on your water, you may consider moving the dock out to avoid it getting hit. Shifting ice can sometimes be 5 miles wide and will destroy any structure in its path.



By: Dave Darr