Marine plywood, or marine ply, is a specialty sheet good often used for boat building and other outdoor applications where the plywood will come into contact with water. It differs from other plywood by the species of wood, number (and thickness) of layers, and the adhesive used in manufacturing.

Marine Plywood Core

Marine plywood comprises many thin layers, which reduces large knots or voids in the core. This helps prevent water infiltration and reduces the risk of rot and delamination. Additionally, manufacturers produce marine ply with glue that is weather and boil proof (WBP). Testers subject WBP glue to a prolonged period of boiling to ensure it withstands without delamination.

Marine Plywood Species

Manufacturers can make marine plywood from any species of wood that has rot-resistant properties. They commonly make it from a tropical species of mahogany such as meranti or okoume.

Meranti: A wood species found in Southeast Asia that has similar properties to genuine mahogany. Boat builders often use meranti for boat interiors because of its heavier nature.

Okoume: An African hardwood that is lightweight and bendable. For these reasons, boat builders use it on boat exteriors and finish it with epoxy or fibreglass.

Teak and Holly: A combination of two wood species joined together creates the stunning stripes teak and holly are known for. Boat owners mainly use it for nautical interiors including cabinetry, hatches, and flooring.

If manufacturers make the plywood of both meranti and okoume, they will sell it as mixed species.

Exploring the Different Grades

The quality (and appearance) of each face determines plywood’s grade, using an A–D scale (with A being the highest quality). Grading for marine ply is usually A/A or A/B. The first letter designates the grade of the top side, while the second letter designates the grade of the bottom side.

Grade A: Smooth, sanded surface without knots. 

Grade B: Smooth, sanded surface. The face can have repaired defects (up to 1”). 

Did you know you have to finish marine plywood?

Marine plywood is water-resistant but will not withstand long-term water exposure without proper finishing. Epoxy, fibreglass, paint, varnish, or polyurethane are all acceptable finishes to protect plywood. All faces and edges need to be sealed to prevent moisture from penetrating the core.

At The WoodSource we stock meranti, okoume, and mixed marine ply in thicknesses varying from 4mm to 18mm. Stop by our showroom in Ottawa, or shop online from the comfort of your couch.

If you have questions about marine plywood or need help with a project, don’t hesitate to reach out to one of our knowledgeable sales staff.