What Is Marine Grade Plywood?

Author:

Dmitry

Updated:

October 25, 2024

I have used marine-grade plywood many times for different projects including making wooden boats, kitchen cabinets, flooring, and docks among other projects. It is one of the most reliable materials that on exposure can withstand harsh weather conditions.

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Marine-grade plywood is a high-grade quality hardwood panel that is made by alternating sheets of veneer such that the grains alternate in the process of lamination. The veneer or plies are bonded by waterproof glue under heat and pressure to produce a marine-grade plywood type that is can withstand snow, moisture, and rain.

When it comes to using it to make a boat; from building the hull, laying the bulkheads seats, and customizing the storage compartments, to rudder shaping, marine-grade plywood plays an important role throughout the process due to its unique qualities compared to ordinary plywood.

What is special about marine-grade plywood? Hold on to the end of this article to get to understand the special features, and what makes it different from regular plywood.

Unique Qualities of Marine Plywood

Marine plywood is highly regarded for its strength and quality. It is strong, durable, and has other features that are rare with other plywood types. Some of its unique qualities include the following:

Water resistance

The marine plywood results from a process of laminating plies of veneer together using waterproof glue and under heat and pressure. This results in durable Marine grade plywood having the ability to resist water damage or moisture on repeated exposure. It is, however, not waterproof but can withstand very high humidity.

Bore and termite-resistant

The making of marine plywood uses a technology that makes it hard for the termites to bore into. The gluing, heat, and pressure applied during manufacturing and all the treatments make it strong and termite-resistant.

Impact-resistant

The design of this plywood yields a strong, hard, and scratch-proof plywood that is not only resistant to impact but also resists wear and tear. It is created to withstand greater force than other plywood types.

Different Grades of Marine Plywood

There are five grades of marine plywood. This grading system is useful when determining the quality of marine plywood for specific projects.

A-A grade

This marine plywood comes in two sizes. That is 4 x 8 feet and 5 x 12 feet. It is one of the high-quality plywood types that suit different functions including bathrooms, patios, decks, and boats just to mention a few of its functions. It is ½ inches in thickness and does not have open knots.

A-B grade

This marine-grade plywood type almost has the same features as the A-A grade type. The difference is only in the thickness. The A-B grade comes with ¾ inches of thickness and hence is suitable for specific projects such as making cabinets and decks among other uses. Also, it does not have open knots, just like the A-A grade quality.

B-B grade

When it comes to quality, this is one of the lowest and does not serve more sensitive projects like the making of wooden boats. It is, however, useful in projects like patio chairs and tables among other similar projects. B-B grade plywood is also referred to as face-back marine plywood.

Medium-Density Overlay

The Medium Density Overlay (MDO) is good for most outdoor furniture projects. It is great quality plywood that resists moisture, chemical damage, as well as wear and tear. This grade also has a varying thickness and comes in a standard size of 4 x 8 feet.

High-Density Overlay

High-density overlay (HDO) plywood also comes in varying thicknesses of ½ or ¾ inches. They also have a standard size of 4 x 8 feet. On the physical appearance, the High-Density Overlay is smooth and shines more than the Medium Density Overlay plywood.

Is Marine Grade Plywood Waterproof?

Marine plywood is not waterproof. However, it can tolerate rain, moisture, and snow among other harsh conditions when exposed repeatedly.

Though it is not waterproof, it can resist water damage. The waterproof glue that is used to bold the plies or veneers together does not delaminate when it is exposed to water for long.

What is Special About Marine Grade Plywood?

Marine-grade plywood is special in that it comes with unique features that are not found in regular plywood. From the design, it utilizes special techniques that are not common with regular plywood such as heat treatment and pressure.

This technique – the heat and pressure method, plus the use of waterproof glue yields a sturdier and high-grade quality plywood that can tolerate extreme humidity, rain, and snow.

What is Marine Plywood Used for?

Marine-grade plywood has many uses. The quality makes it useful for boats, outdoor furniture such as patios, decks, porches, bathrooms, kitchen cabinets, and backyard playhouses among other wooden constructions.

Difference between Marine Grade Plywood and Regular Plywood

There are quite a number of differences that exist between marine-grade plywood and regular plywood. This is in terms of the following features:

Number of layers

The marine grade plywood is made up of at least five layers or plies. These layers are bonded together to form a strong and sturdy panel without voids. Regular plywood on the other hand can have three or more layers that are thin and usually have voids.

Glue

Marine-grade plywood uses different interior glue that is waterproof to stick the plies together. This is different from regular plywood. On a similar note, both use the same exterior glue.

Finish

Regular plywood can have different finish levels on both sides. The marine-grade plywood only has the same finish on both sides.

Cost

Marine-grade plywood is more costly than regular plywood. This is because of the difference in quality. A marine-grade type would cost about four times the cost of regular plywood of the same size.

This is one of the main reasons, why people are looking for alternatives to marine-grade plywood. Check this article with 9 alternatives to marine plywood we have found if you are looking for a good one.

Advantages of Marine Plywood

Marine-grade plywood comes with several advantages over other plywood types. That is why they are used in most projects that require quality and durable wood like in the construction of wooden boats. Some of the advantages include:

Water-resistant and does not get damaged on exposure to rain or snow.
Comes with an excellent finish that you can use without the need for painting.
It is flexible and does not crack when pressed.
It is termite resistant and that makes it last longer.
There is uniform strength throughout the plywood.
Useful in many outdoor projects due to its good density and resilience.
A hard and dense outside layer helps in resisting impact.

Disadvantages of Marine Plywood

Despite the many advantages, marine-grade plywood also has its weak side. The first one is the price, of course, due to the quality, the price is way more compared to the regular plywood. The other disadvantage is that:

It is not waterproof. It is just resistant to water damage. It can only stay intact without delaminating when placed in water due to the waterproof glue that is used in the manufacturing process.

Final thoughts

Marine-grade plywood is, as I have mentioned, a high-grade quality hardwood panel that results from alternating plies or veneers and bonding them with waterproof glue under heat and pressure. This results in durable grade plywood that is tolerant to high humidity, rain, or snow and hence useful in many outdoor and indoor projects.

You can use marine-grade plywood to accomplish several projects like building wooden boats, kitchen cabinets, bathrooms, decks, and other outdoor furniture.

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