How Do You Seal Marine Plywood?

Marine-grade plywood is a type of wood that is waterproof, rot-resistant, and extremely strong, making it ideal for boat and dock construction. It must be properly sealed using the appropriate products and techniques to keep it in good condition.

Start by cleaning the surface with a mild detergent and water, then apply the sealant using a brush or roller. Make sure to use epoxy resin moisture, marine grade, or a two-part polyurethane sealant because these are specialty products that provide the best protection for your boat and dock.

In this article, we will discuss the steps you need to take to properly seal marine plywood and the different types of sealants you can use. So, if you’re ready to start, let’s dive right in and learn how to seal marine plywood!

How Do You Seal Marine Plywood.

How Do You Seal Marine Plywood? A step-by-step guide

Sealing marine plywood is an important part of protecting it from the elements. It is a special type of plywood specially treated to withstand the rigors of being in an aquatic environment.

It is often used for boat building, docks, and other marine applications. Sealing marine plywood is a relatively simple process that involves a few basic steps. Here’s a step-by-step guide to sealing your marine plywood.

Step 1: Clean the Plywood

The first step in sealing marine plywood is to ensure it is clean. This means removing any dirt, debris, and any other contaminants that may be on the surface of the plywood. Use a stiff brush and some soapy water to scrub the plywood surface. Make sure to rinse it off thoroughly after cleaning.

Step 2: Sand the Plywood

Once the plywood is clean, you’ll need to sand it. This will help to create a smooth surface that will allow for a better sealant application. Use medium-grit sandpaper and sand the surface of the plywood until it is smooth. Make sure to remove any dust created from the sanding process with a damp cloth.

Step 3: Apply the Sealant

Now that the plywood is clean and sanded, it is ready for the sealant. Most sealants are designed for marine plywood, so pick one for this type of wood. Apply the sealant to the plywood surface in a thin, even coat. Make sure to apply it evenly and in the direction of the grain.

Step 4: Allow the Sealant to Dry

It is important to give the sealant enough time to dry after application. Drying times can range greatly depending on the type of sealant used, from a few hours to several days.

The manufacturer’s instructions and suggestions regarding drying times should be followed to guarantee that the sealant has had enough time to dry. Inadequate drying of the sealant could lead to problems later on and compromise the project’s overall integrity.

It’s also important to remember that extra drying time might be required in some circumstances, such as in humid or cold climates.

Step 5: Inspect and Re-apply

After the sealant has dried, inspect it for any areas requiring reapplication. Look for any areas of the sealant that have gaps, cracks, or other imperfections. Repeat the process if any areas require re-sealing, applying the sealant generously and evenly to the affected areas.

It is recommended that you inspect the areas again to ensure that you have achieved the desired results.

What type of sealant can be used on Outdoor Marine Plywood?

For optimal protection of outdoor marine plywood, it is recommended to use a high-quality sealant. Ideal sealants for marine plywood include waterproof, UV-resistant products capable of withstanding extreme temperatures.

Epoxy sealants are a popular choice for marine plywood, as they are extremely durable and provide a glossy finish to help prevent wood rot and decay. Additionally, silicone-based sealants are recommended for marine plywood, as they are extremely flexible and can withstand temperature fluctuations without cracking.

No matter what type of sealant you decide to use, it’s important to ensure that it is applied according to the manufacturer’s instructions to guarantee the best possible results.

Can the Same Method Used to Seal Marine Plywood Be Applied to Adirondack Chairs for Weatherproofing?

When weatherproofing old Adirondack chairs, suggestions for sealing marine plywood may not be suitable. Since Adirondack chairs are often made of different materials, it’s best to use a method specifically designed for wood. Consider using a wood sealant or outdoor varnish to protect the chairs from the elements.

Is Thompson’s Water Seal Clear Wood Protector suitable for Marine Plywood?

Thompson’s Water Seal Clear Wood Protector is an excellent choice for sealing marine plywood. It is designed to protect the wood from water and sun damage and can be used on various wood types, including marine plywood.

The sealant forms an invisible barrier that repels water and moisture, making it an ideal choice for outdoor surfaces and coastal climates. The formulation is also mildew and algae-resistant, so it is well-suited for marine plywood, which is often subject to high humidity levels.

Additionally, Thompson’s Water Seal Clear Wood Protector is easy to apply and provides long-lasting protection. With regular maintenance and care, this product can help protect marine plywood from the elements and keep it looking great for many years.

How long does sealed marine plywood last?

Sealed marine plywood can last anywhere from 3 to 5 years, depending on the type of sealant used and the environmental conditions it is exposed to. Marine plywood is typically treated with a water-resistant sealant to protect against damage from moisture. Still, the type of sealant and the environment can affect the longevity of the wood.

For example, if the plywood is exposed to direct sunlight or saltwater, the sealant can degrade faster, and the wood may last for fewer years. The type of sealant used can also determine how long the wood will last. High-quality ones can protect the wood for up to 5 years, while lower-quality sealants may need to be replaced more frequently.


Sealing marine plywood is an important process that should be done to ensure its longevity and protection from moisture and other elements. The best sealant for outdoor marine plywood is a waterproof sealant such as Thompson’s Water Seal Clear Wood Protector.

When properly sealed, marine plywood can last for many years. It is important to regularly inspect and reapply sealant when necessary to keep it in top condition. Following the manufacturer’s instructions when applying sealant is important to ensure the best results. Thank you for reading!

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