What Is Marine-Grade vs Pressure-Treated Plywood?

Plywood is one of the inventions that have a place in our daily lives. Marine-grade plywood is a type that is good for certain specific uses.

What exactly is it? How is it different from the regular stuff? The key component here is that the glue which holds the veneers together is waterproof. It is always smoothed out. It is made of a type of wood that doesn’t easily allow fungus growth, even in moist environments.

Where can you use this, and what else is there to know? Here you can find more detailed information about it. You’ll learn where to use marine-grade plywood. We’ll also cover the common differences between marine-grade plywood and the regular type.

What is the Difference between Marine Grade Plywood And Others?

plywood picture

This is the type that handles contact with water better than any other. This plywood is sturdier and is always made of high-quality wood of certain tree varieties.

During the production, the thin veneer sheets are put on top of each other perpendicularly. They go through a process called cross-lamination. This process makes it sturdier. Heat and pressure play a critical role in the production process.

There are three key points for it to be certified as marine-grade. The first is that the glue must be waterproof. The second is that there should be no air left between the glued veneers. The inside veneers should be made of good, quality wood.

These are critical components since they ensure the wood in contact with water will keep up with the harsh environments for a long time. The waterproof glue should endure a “Weather and Boil Test,” which is a stringency test. The most commonly used type of glue is phenol-formaldehyde.

plywood seen from above

The use of waterproof glue is important. It ensures the plywood won’t delaminate or divide into individual layers under harsh conditions. Such conditions include high temperatures or moist environments.

Voids are an important aspect since the wood can absorb the water. If there are gaps between glued veneers, the water can pass through the exterior veneers to the inner veneer layers. It makes it brittle or very open to possible fungus infection and rot.

The last most important aspect is that it isn’t treated with any chemicals beforehand. It is about maintaining the quality.

Another important aspect is the overall quality of the veneers. Knot sizes and frequencies should be controlled. There are rules for repairing inner veneers. The thickness and number of plies are also controlled.

Certain types of trees are preferred for the production:

  • fir
  • Okoume
  • and meranti

Let’s take a better look at them.

Douglas Fir

This type is used as it’s very strong. The other reason Douglas fir is chosen is that it bends well and isn’t too heavy. It makes it a good choice for boat hulls or anywhere the wood should be bent.

In addition, it is very weather-resistant. It is generally cheaper than the other options as well.


These trees are native to Africa, and they are good quality materials for the product. It has a similar look to mahogany. The best thing about Okoume is that it is quite light. It makes boat interiors and exterior design excellent since it doesn’t add too much weight.

It also looks good after it is laminated. It has a finish like glass. The Bruynzeel option is the best example of this.


This is another type of tropical tree that is used for high-quality production. The main advantage of meranti is that it’s much sturdier than Okoume, especially against bending. However, it’s also heavier.

It was first developed by Cornelis Kees Bruynzeel, who studied woodworking and was an avid sailor. Bruynzeel developed the water-resistant glue and made the first marine-grade plywood.

Let’s take a closer look at the grades.


First of all, there are different thicknesses of this type. The thickness comes in increments of 1/8”. It ranges between ¼ and ¾ inches thick. and The available width and height are 4”x 8”. Its price changes according to thickness and size.

When you’re planning your construction, you should take the thickness and grade into consideration. These are the grades:

·        A-A: This grade is usually 1/2” thick and comes in 4” x 8”.

·        A-B: The size stays the same as A-A, but the thickness is 3/4”. It has no knots, and it’s stronger.

·        B-B: You can also find these under the name of face-back marine plywood.

·        Medium-density overlay (MDO): This comes in the regular dimensions, but the thickness varies. You can find it with thicknesses ranging from 3/8” to 1”. It has a high-quality thermosetting impregnated with resin fiber overlay.

·        High-density overlay (HDO): This grade is shinier than MDO because it is impregnated with more resin. The dimensions are the same, and the thickness varies from ½” to 3/4”.

·        D: The least expensive type.

Like this guide about choosing marine plywood, you can check similar articles about engine-driven welders and extension cords. We also have articles on gauge wire or cassette toilets.

Best Uses

We’ve introduced you to what it is made of and which properties make it different from the regular stuff. You can learn more about using this type of wood for your next construction project.


Because boats are always in contact with water and moisture, this is the most common use. Note that this is why Bruynzeel developed it in the first place.

This type is 100% waterproof, required for the rough conditions. It is also quite pliable. You can even use it in a boat’s hulls or other curved parts. To properly use it in boats, you should seal it properly.


Docks are another place where the wood is constantly in contact with water. Since you can use it for boats, it makes sense that you can also use it to build your dock.

The biggest reason that you should choose this over others when you’re building a dock is that it doesn’t require sanding. It saves you the work of sanding every year. Because the type of wood used is weather-resistant, you won’t have rot or warping problems.


When we say interiors, we mean the kitchen and bathroom’s moistest and wettest parts of the house.

Suppose your bathroom floods or you like to take steamy showers. You may consider having bathroom furniture made out of this weather-resistant material. You can try it as a replacement for flooring or siding. This choice will also reduce the mold and rot in the bathroom.

As for kitchens, it is also a good choice for your next remodeling project. Given that Bruynzeel developed marine-grade plywood for kitchen use, it makes a lot of sense to use it there! You can use this to replace your cupboards or as a replacement for flooring or siding.


In addition to the interior use, you can use it in exterior areas of your house. It’s commonly used for decks and porches.

Because it comes in various sizes, it’s rather cheap to cover all your exterior parts of the house with these boards. It will be very weather-resistant if you choose to do so. The boards don’t rot easily!

In addition to flooring or siding, you can always make yourself a nice fishing dock out of this material. If you have a pond or body of water where you can regularly go fishing, it’d be a nice addition.

To renovate your house or build your boat, you may require additional equipment.

Now, let’s take a closer look at the differences between pressure-treated and marine-grade plywood.

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Pressure Treated versus Marine-Grade

plywood sheet

For the untrained eye, it may seem like a good idea that you can repair your boat with pressure-treated plywood. However, the pressure-treated options and marine grades are not interchangeable. These two have very different places where each type should be used.

To begin with, the biggest difference between these types is the ways they’re chemically treated. Marine-grade is rarely chemically treated during production, whereas pressure-treated plywood is. This changes the overall quality and water resistance. Contact with water constantly will wear out the chemicals.

Another important difference is the overall water resistance capacities of each individual product. For marine-grade plywood, water-resistant glue is used. It gives it very distinctive features. Pressure-treated plywood isn’t necessarily produced with water resistance in mind.

Pressure-treated plywood is generally made out of softwood. This allows chemical treatment. It means water penetration between the different veneers should be considered. In contrast, marine-grade uses harder types of wood. It alleviates the water penetration problem.

In addition to the hardness, it generally has thinner veneers than the regular pressure-treated wood. This is another reason why it is sturdier than other options.


Another critical difference is the number of plies. During the production, the number of plies is controlled to increase the sturdiness. It isn’t the case for pressure-treated wood.

A thing that the two do have in common is rot resistance. The main reason pressure-treated plywood will rot and be insect-resistant is the chemicals used in the production. Given that constant water contact will wash away the chemicals, it’s expected that the pressure grade will lose this ability over time.

Marine-grade is developed and used for places with a lot of exposure to water. It’s the reason it has the name that it has.

Check out our guide on air conditioners or generators if you consider a home improvement project. 

Exterior-Grade versus Marine-Grade

At first glance, you may not recognize the key differences between exterior grade and marine plywood. When you start taking a closer look, it becomes evident that there is a range of differences.

Let’s start with why these types are sometimes considered interchangeable by untrained eyes. The reason that they are often compared is due to the nature of their general weather-resistant features. Exterior-grade is also made of A-bond glue, which makes it water-resistant in the first place. It is designed to withstand the unpredictable forces it gets exposed to outside.

Unfortunately, the similarities end there. To be labeled as marine, it has to meet some strict standards. An exterior grade doesn’t need to satisfy these criteria.

The criteria here are that there must be no void between the veneers. The second is that the veneers must be of the highest quality. The last is that the glue needs to be waterproof. The exterior grade won’t be cut because of the quality of the wood.

In addition to the quality of the material, the exterior grade may have some gaps created during the lamination process. Using them for a boat is bad as the water can reach the inner veneers. Using marine-grade ensures that the water will never reach the core of the ply, hence any rot.

Another important fact here is that it will never have aesthetic problems. We usually think of the finish, the plies, and the knots as aesthetic problems. You can use exterior grades for some outdoor purposes, though. You would never use them for the interior of a boat.

Marine-grade will never have any or only very few of them. On the contrary, an exterior grade may have knots as big as 1”. This entirely changes the look when that is the case.

The exterior grade may replace cheap marine grade plywood in an outdoor structure. It will never fully replace it for all uses. If you are planning to build your boat, you shouldn’t replace it with something that doesn’t have the same level of water resistance.

So, let’s say you’re on a tight budget. What other materials can you look for instead?

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Although it is the best for various jobs, sometimes you may not easily procure marine-grade plywood. Perhaps you are on the hunt for cheaper alternatives. These alternatives may not fill the shoes easily, but they may still serve as reasonable alternatives.

Polyurethane foam made by 3M

The first alternative that you can look for is polyurethane foam made by 3M. This is a lighter and rot-resistant alternative. These boards have fiberglass reinforcement, and they are practical or high strength applications purposes. You can especially choose this if you have weight concerns you need to consider.

These foam boards also come in the same sizes as marine-grade plywood, 4” x 8”. They are perfectly straight and easy to shape with tools. You should use the right-grade screws to secure them.

Another alternative is fiberboard. These have a lot of similar characteristics. However, they are not 100% wood! Fiberboards contain wax resin to increase their strength. It is a special kind. It’s broken down into fibers from softwood, and these fragments are mixed with a wax resin to make up the boards.

Fiberboards can give you the feeling while being a viable alternative. You can also find them as sheets, and they are heat-resistant. For better insulation, you can use these sheets under waste oil heaters or hot water recirculation pumps.

Ribbon grain

Ribbon grain is also another alternative. It gets its name from the appearance as the grain is shaped like ribbons. The vertical stripes run along with the wood. It is also a very smooth type, and the appearance is alluring! They don’t have all the same characteristics. It is much cheaper than marine-grade plywood.

Fiber cement boards aren’t technically plywood, but they contain a good amount of wood material. They are good for exterior use, such as on walls or ceilings. It is a special type of board since it’s cement mixed with fibers. These are quite sturdy.

You can sometimes replace marine-grade with other types of material while getting the features you are looking for. You should always keep the project in mind and make your choice accordingly.

The next and last question remains, where can you find them?

Where to Buy It Marine-Grade Plywood?

There are several ways you can buy it. You can either look for the sellers on Amazon or go online and find the nearest distributor. Now you know what to look for when you’re buying it. It should be easy to see if the seller’s descriptions match your needs!

We have a couple of suggestions for you. When looking for your distributors, first ask them if they supply Bruynzeel. It is a reputable brand. You can buy those while knowing you are getting the quality you want.

If you don’t have any local suppliers, you can always check out big distributors like Amazon and Home Depot. For higher-end stuff like Okoume, you may have to check for a local supplier as we haven’t found any reliable sources online.

3/4”, 2’ x 4’

Capitol City Lumber makes this certain product. It’s ¾” thick, and the sheet’s dimensions are 2’x4’. This product has a clear and smooth finish. It’s not knot-free and has patches of blemishes, however. Nevertheless, it’s marine-grade because of the exterior phenolic glue and the fact that there aren’t any voids between the plies.

In Conclusion

It is a good choice if you want to redecorate the parts of your house that get exposed to moisture. We’re thinking of your home’s exterior. It’s the perfect material if you dream of building a boat or kayak to take out on a lake near where you live. We hope that this article helped answer many of the questions you may have had.

Additionally, we would like to tell you a little bit about the mission that we are on here at Atlantic Aspiration. We have many other features that we would love for you to explore while we have your attention!


Is marine-grade plywood waterproof?

Yes, marine-grade plywood is made from water-resistant plywood. It’s coated with waterproof grade glue to seal it against any moisture completely.

Is treated plywood the same as marine plywood?

No, the material and glue used in both differ slightly. Treated plywood uses softer wood to allow for mold and fungal remediation chemicals to be absorbed. The glue used for treated plywood is UF resins and is cured with a cold method. But for marine plywood, the glue is waterproof phenol-formaldehyde glue cured using high heat and pressure.

What is the thickness of 3/4 marine plywood?

It is 19mm thick.

Do they make 1/2″ treated plywood?

Yes, a standard thickness of ½” is available in treated plywood.

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