How to Waterproof Wood for a Boat [3 Simple Steps & Tips]

how to waterproof wood for a boat

There will be times when you’re going to have to make repairs on your deck. If there are wooden parts on your watercraft, these will typically be the first to require replacement. It might seem like a complicate process, but you can actually get the job done on your own so you can cut down on repair costs.

What’s most important when replacing plywood on your boat would be to waterproof the new part first. Plywood that isn’t treated prior to installation will become waterlogged, rotten, and weak, which could put the rest of your boat in jeopardy. Find out how to waterproof wood for a boat to prepare for that repair job.

Why is It Important to Waterproof Wood for a Boat?

Waterproofing marine plywood for a boat probably isn’t something you ever thought about doing. But that doesn’t make it any less important. There are a number of reasons why you should make sure to waterproof wooden deck parts before installing them in your boat, including:


The first and most obvious reason would be protection. UV rays, water exposure, and humidity in a marine environment all work together to degrade plywood. Without waterproofing sealer, there won't be anything to protect your wood against harmful rays and water, leaving it to succumb to damage in as little as a few months, depending on how often you use your boat.


When humidity, moisture, and water damage rot the surface of plywood that isn’t treated with water resistant sealer or epoxy, you open up the way for neighboring parts to be subject to the same damage especially if you've got a wooden boat. Rot can impact the integrity of other areas of your boat which may require replacement and repair as well.

Cost Effectiveness

Sure, you could always just replace a wooden boat piece when it’s broken, rotten, or waterlogged. But when it becomes a routine thing to change a piece of wood on your boat, things can get expensive over a long time. Waterproof sealer or epoxy just guarantees that you won’t have to worry about making costly repairs so often, offering a long term solution for wooden boats.

What You Need to Waterproof Marine Plywood for a Boat

If it’s your first time waterproofing a wooden boat hull, you might think there are a ton of materials and tools involved. But you can actually get all that you need with just the loose change in your pocket. Here’s what you’ll need to protect that piece of lumber:


You’re going to have to prep the wooden board before you start water proofing with epoxy. If you’re refurbishing wood for the project, then sanding away any paint or treatment on its surfaces can help the sealing agent protect your boat from water and moisture damage. Rough grit sand paper should help you get rid of major inconsistencies on the surface of the wood, while fine should help smoothen the wood surface and prep it for treatment.

Clean Rag or Cloth

Any old rag will do, so you can actually just take an old shirt for the process. If you’re feeling fancy, a set of microfiber towels can be a good way to wipe off debris on the wood surface and dry the piece of water.

Sealer or Epoxy

Pro Marine Supplies Epoxy

Quality wood sealer or epoxy shouldn’t be too hard to find. They should have it at your local hardware store, boats supply store, or you can buy it online. There are lots of different stain colors to choose from, so make sure you consider your boat’s aesthetic before you decide on a particular color. Others come as two parts that you mix together.

Look for something like the Pro Marine Supplies Epoxy Resin.

Paintbrush or Roller

To apply the sealer or epoxy, you’re going to need a paint brush or a roller. A regular paint brush should do, but if you want a smoother, more even finish, then you can go for a paint roller.

How to Waterproof Wood for Boats

waterproofing a wooden boat hull

Once you have everything you need to get the job done, it’s time to get started. Remember though that the process of water proofing wood for a boat might take more than just a day. So be prepared to shell out up to a week if you’re planning to squeeze the task between other chores and obligations.

1. Prepare the Boat's Wood

Boat's wood that’s rough, covered in marine waterproof paint, or previously treated will not properly take the water proofing seal. So before you slather on product, it’s important that you sand all of the wood’s surfaces.

If there's a thick layer of paint, use a scraping tool to get rid of the hardened paint layer. Take a rough grit sandpaper to sand obvious blemishes on the surfaces of your boat's wood. Make sure you get the edges and ends of the wood grain where roughness and splinters typically abound.

Then when all of the major issues are addressed, you can go ahead and move on to the fine 80 grit sandpaper. Sanding with this should help you achieve a smooth finish that will take to the sealant more readily.

2. Clean the Surfaces

Once you’re done sanding everything down, it’s important that you remove any debris, dirt, paint pieces, or dust on the surface of the wood. All of these things can get in the way of the sealer, working against the stuff so that it doesn’t get absorbed into the wood itself.

Take your cloth and wipe off any of the debris on the surface of the wood. If you want to take it the extra mile, you can skip the cloth and bring the piece outdoor to clean it with water. Just make sure you leave it to dry through and through before you move on to the next step.

3. Apply the Sealant

When all of that is over with, you can move to applying marine waterproofing sealer. Use a paintbrush or roller and apply a layer of the sealant on the wood’s exposed surfaces. Some boat owners find that it’s better to paint the seal to one side and leaving it to dry before applying to the other. Just make sure you also get all of the edges.

Depending on the thickness of your wood, it’s important that you repeat the process. Most marine plywood pieces require 3 to 5 coating of quality product for proper seal. But you can’t apply all the layers all at once. So you’re going to have to wait for each previous layer to dry before you apply the next one.

Sealing product can take up to 10 hours to completely cure, depending on the instructions on the label. See to it that the previous seal coat has dried up completely on the surface before you go ahead and apply the next coat of epoxy with your paint brush. Slathering on another coat of seal before the last one is dry could lead to poor waterproofing, leaving your wood penetrable to moisture.

Tips for Waterproofing Plywood for a Boat

If it’s your first time waterproofing plywood, you might feel a little clumsy going through the process. There are lots of little details that might not seem too obvious right off the bat. So try to consider these tips before you get started on the seal project:

Wear Protective Gear

Marine waterproofing seal is anything but pleasant to the senses. Some people might experience irritation to the respiratory system, while others feel irritation in the eyes even without direct contact. This comes as the result of fumes that come off of the product. Protect your nose, mouth, and eyes, and wear a set of gloves to keep the stuff off of your hands.

Read the Label

The instructions provided here should give you a general idea of how to go about properly waterproofing marine wood. But there are some products out there that have their own instructions all together. Some might require that you mix in separate ingredients, others might need more time to cure, and then there are those that require a coating of hardener. Some are even developed for just certain types of plywood, so make sure you thoroughly take the time to understand the product.

Know What Type of Wood You're Working With

Not all wood will require treatment. For instance, marine plywood should be good enough at fending off water damage on its own without the need for extra treatment. If you're using regular plywood, the general rule is that the thicker it is, the more layers of sealant you'll need. Don't be afraid to ask a professional to find out how many coats you should apply on your specific plywood.

Plan Ahead

It's not going to be an overnight job, that's for sure. Sealant will have to cure for up to 10 hours or more, depending on the product you've chosen. And because most plywood will require 3 to 5 layers of sealant, it's going to be a two to three day job, at the least. Map out your schedule to make sure you have enough time to work on the wood once the previous coats have cured.

Work Outside

The fumes from sealant can get trapped in a tight environment, causing irritation and perhaps even health risks in certain sensitive individuals. Avoid working in enclosed spaces. See to it that you're in a clean, well-lit, well-ventilated, outdoor environment where fumes won't have a chance to build up in the air.

Check the Weather

A sealant will dry up best when it's left in a place where there's lots of sun and heat. If it's the rainy season, you might want to wait for a sunny weekend to get started on the job so you can give the sealant layers a better chance at drying up.

Cover All Edges and Sides

Leaving even the smallest surface of your plywood untreated leaves it vulnerable to water penetration. It's always best to apply sealant to a boat plywood piece while it's not installed on the boat so you can thoroughly get all of the exposed sides and edges of the whole plywood. See to it that the sealant soaks through the ends of the plywood where water damage typically starts. That's also why sanding is especially important.

Ready for the Water

There are lots of vintage wooden boats out there that are still operational after many years thanks to the many layers of waterproofing treatment coating their plywood. But because not a lot of boat owners know how to waterproof wood for a boat, they end up passing the job to a pro who might charge way more than the labor entails. Fortunately for you, that shouldn't have to be a problem. Just keep these tips in mind and you should be able to create a watertight seal without having to spend too much.

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