Marine Grade Plywood: Everything You Need to Know

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We’re all familiar with plywood, but did you know there are different types of it? Plywood comes in grades and fits into 1 of multiple different categories, depending on its composition and how it was made. Marine grade plywood, for instance, is the highest grade of plywood and differs from other types of plywood in many ways. 

In case you weren’t aware of marine grade plywood and what gives it its name, let’s go through a complete breakdown of everything you could hope to know about marine grade plywood. 

What is Marine Grade Plywood?

Marine grade plywood is essentially the highest-quality plywood you can get. It’s called “Marine grade” in part because it has to be fully capable of standing up to rain, snow, and moisture on a regular, repeated basis in order to qualify. This isn’t the only qualification a piece of plywood needs to meet to be labeled as marine grade, however. 

Marine grade plywood can only be made with Western Larch or Douglas Fir wood. It also must have 5 or more layers, with far fewer air pockets and small voids than regular plywood. It can have some knots in the exterior plies, but no knotholes are allowed.  It must be bonded with waterproof glue. 

How is Marine Grade Plywood Made?

Marine grade plywood is made by arranging 5 or more plies of Douglas Fir or Western Larch wood in a perpendicular manner so that the grains are alternating from vertical to horizontal. This perpendicular arrangement of the individual plies is what gives the plywood increased strength. 

The plies are bonded together under heat and pressure, using a special type of glue that is waterproof. A water-resistant finish is then added to the exterior. The waterproof glue as well as the lack of voids, knots, and air pockets are the defining features that separate Marine grade plywood from various other types of plywood. 

Also, the fact that Marine grade plywood is made with more, thinner layers of high-quality wood as opposed to fewer, thicker layers of lower-quality wood is what sets it apart from other types of plywood. 

Marine grade plywood is not to be confused with similar types of plywood like pressure-treated plywood. While Marine grade plywood is technically “pressure-treated”, it is not soaked in or made with any special chemicals that increase its resistance to rot, mold, and moisture. The term “pressure-treated” is usually used to refer to plywood that has, in fact, been chemically soaked to improve its durability. 

Pros and Cons of Marine Grade Plywood

Marine grade plywood
Image Credit – blacktownbuildingsupplies.com.au

Durability is the main upside of Marine grade plywood. It’s expected to last much longer outdoors than almost any other type of plywood. Because of it’s durability and resistance to moisture, Marine grade plywood is often used to build boats, homes, and more. The lack of knotholes and air pockets make it much more structurally sound.

The appearance of Marine grade plywood is also much better than that of regular plywood. It’s sanded on both sides and takes paint very well. It looks so good that you can even use it as top floor material. 

It’s far less splintery and smoother than regular plywood. Marine grade plywood is also easier to cut and bend, making it much more suitable for a wide variety of construction projects. It’s also available in many different thicknesses and sizes. 

Because Marine grade plywood is so high-quality, it may not be readily available in your area if you’re somewhat rural. It’s also more expensive than regular plywood.

Grades of Marine Plywood

  • A-A: This grade of Marine plywood comes in ½ inch thick pieces and is usually found in either 4×8 or 5x12ft pieces.
  • A-B: This grade is found in the same length and width dimensions but is ¾ inch thick instead of ½ inch. A-B grade Marine plywood is stronger and heavier than A-A.
  • B-B: This grade of marine plywood is also known as face-back Marine plywood. 
  • MDO: MDO stands for medium-density overlay. This is exterior-grade plywood that has been made with a resin-impregnated, high-quality thermosetting fiber overlay under heat and pressure. The veneer beneath this fiber surface is smooth and takes paint very well. 

This grade is both durable and strong while possessing dimensional stability as well. MDO is usually found in 4x8ft pieces. It can be had in a variety of thicknesses including ¾ inch, ½ inch, ⅜ inch, 1 inch, and ⅝ inch. 

This grade of marine plywood is resistant to chemicals, weather damage, scratching and denting. For this reason, it’s often used for siding.

  • HDO: HDO stands for high-density overlay. 

Cost of Marine Grade Plywood

Marine grade plywood
Image Credit – ohc.net
  • The average ¾ inch thick, 4×8 piece of marine plywood goes for about $100. However, the price can vary from as low as 70$ to as high as $200.
  • A ¼ inch thick piece of 4×8 Marine grade plywood costs around $55 on average.
  • A ⅜ inch thick piece of 4×8 Marine grade plywood goes for about $65.
  • ½ inch, 4×8 Marine grade plywood costs around $77.
  • A ⅝ inch thick piece of 4×8 Marine grade plywood will cost about $84 on average.
  • A ¾ inch thick 4×10 piece of Marine grade plywood will cost about $150. 

Marine Grade Plywood Installation

Marine grade plywood is used in a variety of projects and locations. Its installation process varies based on how and where it’s being used, but it doesn’t require any specialized equipment and can be installed using the same method you would use to install most other types of wood. 

Cut it to size with a jigsaw and cut along the grain lines to achieve a smoother cut. 3-inch exterior-grade wood screws should be used for bigger pieces and exterior projects. 1 screw every 12 inches or so should suffice, and caulk can be used to seal the seams between each piece if necessary. 

Marine Grade Applications

Marine grade plywood
Image Credit – maggiescarf.com

You might expect to see Marine grade plywood used in the installation and construction or birdhouses, furniture, boats, siding for buildings, signs, pergolas, gazebos, and more. Because Marine grade plywood is able to withstand 24/7 immersion in water, you’ll find it in many different docks, piers, boats, lighthouses, and other buildings and features that are constantly exposed to a high level of moisture. 

Bathrooms, kitchens, patios, decks, and porches are also commonly built with at least some Marine grade plywood during construction. These are household areas that see a lot of water and moisture, thus Marine grade plywood makes an excellent choice for their construction. 

Top Marine Grade Plywood Suppliers

1. Chesapeake Plywood

Chesapeake Plywood is a wholesale distributor of a wide variety of different types of wood, including Marine grade plywood. They were established in 2001 and deliver products all across America. They can also arrange exports to international customers as well.

2. Plywood Company

Located in the Dallas-Fortworth area, Plywood company is another leading distributor of Marine grade plywood, among many other products. They have been in business for over 50 years. Plywood Company has been FSC certified since the year 2008. This allows them to ensure the chain-of-custody requirements are met that make their products ”green”. 

Green products allow their customers to obtain more LEED points for using their products, which in turn can lead to government incentives and rewards based around eco-friendly habits and methods. 

3. Cal Panel

Cal Panel is a California-based company that sells wood products, including Marine grade plywood. They stock a wide variety of products that can be categorized as “green” or that contribute to obtaining LEED credits. Cal Panel also offers Formica products, specialty products, and specialty plywood such as “bending poplar”. 

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