Exterior Waterborne Stains: Painting Marine-Grade Plywood

Marine plywood is a variety of plywood that has been treated to withstand moisture and is often used on boats and other items that are frequently in contact with water. Before painting marine plywood, it is important to sand the surface to remove any imperfections and help the paint adhere better. It is recommended to use latex-based paints for marine plywood as they are durable and will expand and contract with the wood, preventing cracking. To ensure a strong bond between the paint and the plywood, a thin coat of latex-based primer should be applied first. After the primer has dried, the surface should be lightly sanded again and any dust removed before painting. While the type of finish paint used is a matter of personal preference, semi-gloss is the most utilitarian choice as it provides a hard finish while also covering any remaining imperfections in the wood.

Sanding marine plywood

Choose the Right Sandpaper:

Start by selecting the appropriate sandpaper grit for sanding marine plywood. It is recommended to use 80-grit sandpaper for this task, as it will provide a good balance between effectiveness and smoothness.

Sand Both Sides and Edges:

When sanding marine plywood, it is crucial to sand both sides of the board evenly. Don't forget to also sand the edges to ensure a consistent finish. This will help create a uniform surface for the subsequent staining, painting, or sealing process.

Use a Tack Cloth:

To make cleaning easier, use a tack cloth to wipe down the plywood after sanding. A tack cloth is designed to attract and capture dust, making it easier to remove sawdust and debris. This step will ensure that the plywood surface is clean and ready for the next steps.

Sanding Technique:

When sanding, use gentle and even pressure, moving the sandpaper in the direction of the wood grain. Avoid applying too much pressure, especially near the edges, to prevent sanding through the thin top layer of the plywood. It is recommended to sand lightly, being extra cautious around the edges to prevent exposing the lower layers.

Wipe Down the Surface:

After sanding, use a soft cloth or a damp cloth to wipe down the plywood surface. Remove any remaining dust or debris. If you use a damp cloth, ensure the plywood is completely dry before proceeding to the next step.

Repeat as Needed:

Depending on the condition of the plywood and your desired finish, you may need to repeat the sanding process multiple times. Lightly sand the surface again if necessary, always being cautious not to over-sand and damage the plywood's surface.

Prepare for the Next Step:

Once you have finished sanding and wiped down the plywood, it is now ready for the next step in the finishing process, such as staining, painting, or sealing. Remember to follow the specific instructions for the product you choose to use.

Sealing marine plywood

Step 1: Sanding

Before applying any kind of sealant or paint, it is essential to sand the marine plywood. Use 80-grit sandpaper to sand both sides of the plywood, including the edges. This process will help create a smooth surface and remove any imperfections. Remember to clean up the dust and debris with a tack cloth after sanding.

Step 2: Applying a Clear, Penetrating Epoxy Sealer

Use a foam brush to apply a clear, penetrating epoxy sealer to the plywood. Saturate the brush and start by coating the top, side edges, and one face of the plywood. Leave the bottom edge uncoated so that you can let the plywood stand and dry. Once the first side is dry, proceed to coat the bottom edge and the other side. This type of sealer is preferred as it penetrates deep into the plywood and requires less maintenance compared to other sealers.

Step 3: Multiple Coats for Maximum Protection

For the best protection, apply additional coats of the sealer. As a general rule, apply as many layers of sealer as there are layers of plywood. Lightly sand the surfaces between each coating to roughen the surface slightly, which will help the next coat adhere better.

Additional Tips:

• If you plan to use the plywood for a project that will be outside, consider using an oil-based stain or a water-based latex paint.
• If you intend to paint the plywood, apply a thin coat of latex-based primer first and let it dry completely before lightly sanding it.
• When painting, use a brush or roller to achieve better thin coverage. Start at the top and work from one side to the other to effectively work in any drips.
• Regularly inspect the marine plywood for wear and tear, and renew the sealant or paint as needed.

Painting marine plywood

Marine plywood is a particular type of plywood that has been treated to withstand moisture. It is often used on boats and other items that are in frequent contact with water. However, it is not entirely waterproof and will need to be painted or sealed to be fully durable.

Sanding

Before painting marine plywood, it is important to sand the surface to remove any imperfections and help the primer adhere more easily. Use 80-grit sandpaper to sand both sides of the plywood and the edges. Then, wipe off the sawdust with a damp cloth or a tack cloth.

Priming

If the marine plywood is likely to come into contact with water, use a latex-based primer. Apply a thin coat of the primer to the wood, allowing it to dry completely before lightly sanding it to roughen the surface. This will help the paint bond with the primer. Remove the dust with a tack cloth.

Painting

The type of finish paint you use depends on your personal preference and how you will be using the wood. Gloss gives the hardest finish but shows imperfections easily. Semi-gloss is a good utilitarian choice as it is almost as hard-wearing as gloss and will cover any remaining imperfections in the wood. Use a latex-based paint if you have used a latex primer.

Apply a thin coat of paint, starting at the top and working from one side to the other to work in any drips. Use a brush or roller for better coverage. Allow the paint to dry, which should take around two to three hours, and then apply another thin coat. Two coats of paint are usually adequate, but you can add an extra coat for greater protection.

Maintenance

The paint should last a few years, but this depends on the use and exposure to the elements. Inspect the marine plywood regularly for wear and tear and renew the paint as needed.

Best paint for marine plywood

Marine plywood is a type of hardwood plywood that is manufactured from Douglas fir or Western Larch. It is often used to build boats, decks, and water-related structures. While it isn't entirely waterproof, it is superior in quality and made with waterproof adhesive, giving it resistance to humid, damp, or wet conditions.

Before painting marine plywood, it is important to sand the surface to remove any imperfections and help the primer adhere better. Use 80-grit sandpaper for this step and remember to wipe off the sawdust with a damp cloth or a tack cloth.

When choosing a paint for marine plywood, consider the type of finish you desire and how the wood will be used. If the plywood is likely to come into contact with water, such as on the exterior of a house, it is recommended to use latex-based paints. These paints are durable and will expand and contract with the wood, preventing cracking. Apply a thin coat of latex-based primer first, let it dry, and then lightly sand the surface to roughen it. Remove the dust with a tack cloth before applying the paint.

The gloss finish provides the hardest finish, but it also shows imperfections easily. For a more utilitarian option that covers imperfections, consider a semi-gloss finish. Just be sure to use latex-based paint over the latex primer.

When applying the paint, start with a thin coat and add additional thin coats as needed. There is no need to sand between coats. Allow each coat to dry for 2-3 hours before applying the next one. Two coats of paint are usually sufficient, but you can add an extra coat for greater protection.

While standard marine paints are available, you can also consider specialised coatings such as Durabak Marine Paint, which is a polyurethane coating that adds durability and is frequently used by the US Navy. It is available in multiple textures and colours, providing a non-skid, protective finish.

Maintaining painted marine plywood

Marine plywood is a variety of plywood that has been treated to withstand moisture. It is often used on boats and other items that are in frequent contact with water. Painting it properly can help increase its durability.

Sanding:

Before applying any paint, it is crucial to sand the plywood to remove imperfections and help the paint adhere better. Use 80-grit sandpaper and sand both sides of the board, including the edges. After sanding, wipe off the sawdust with a damp cloth or a tack cloth. Allow the wood to dry completely before proceeding to the next step.

Priming:

Apply a thin coat of latex-based primer to the wood. Latex-based primers are durable and will expand and contract with the wood, preventing cracking. Give the primer ample time to dry, and then lightly sand it to roughen the surface. This process will help the paint bond strongly with the primer. Remove any dust with a tack cloth before proceeding to the next step.

Painting:

Choose a finish paint suitable for your needs. Gloss gives the hardest finish but shows imperfections easily. Semi-gloss is a good choice as it provides a hard finish and covers imperfections. Use latex-based paint over the latex primer.

Start by applying a thin coat of paint. You can use a brush or a roller for better coverage. Allow the paint to dry, which usually takes about two to three hours, and then apply another thin coat. Two coats of paint are usually sufficient, but you can add an extra coat for more protection.

There is no need to sand between coats. However, you should regularly inspect the painted plywood for wear and tear. The paint's lifespan will depend on its exposure to the elements and usage.

Additional Coats:

To maximise the lifespan of your painted marine plywood, consider adding more coats of paint or sealant. A good rule of thumb is to apply as many layers of sealant as there are layers of plywood. Lightly sand the surfaces between each coating session to roughen the surface and improve adhesion. Remember to wipe off any dust before applying the next layer.

Frequently asked questions