Although it is notwaterproof wood, it is water resistant, lightweight, strong, and virtually defect-free.
It can last 15 to 25 years, especially when coated with a protective finish.
Learn about marine-grade plywood, how it’s different from standard plywood, and where you might use it.
The Spruce / Jacob Fox
Tip
Waterproof glues are critical if you’re building a boat hull with plywood.
The plywood will remain structurally intact if the hull’s protective finish is damaged and the wood gets wet.
What Is Marine-Grade Plywood?
The plies are arranged in sheets or perpendicular layers to strengthen the plywood.
Cross-lamination gives marine plywood even more strength.
The plies may have knots but no knotholes.
What Is Standard Plywood?
Standard plywood is made of only three thick layers of softwoods like pine or Douglas fir.
Marine plywood gives you thinner plies, which makes the wood denser.
In contrast, regular plywood consists of three layers of wood attached to non-waterproof glue.
To preserve marine plywood, use a clear penetrating epoxy.
Waterproof adhesive was invented in 1934, making plywood possible.
By 1954, the industry grew to more than 100 mills, and production approached 4 billion square feet.
Do You Need Marine-Grade Plywood?
Any boat or nautical structure should be built with sealed marine-grade plywood.
If it carries the American Plywood Association trademark as marine grade, that is the ultimate indicator.
It should also be labeled as exterior-grade, waterproof, or “boiling waterproof.”
The veneers used are usually hardwoods like mahogany, birch, or teak.
Birch plywood is a good alternative.
Another choice is MDO (medium-density overlay), a standard plywood coated with weather-resistant resin.
History of APA, Plywood and Engineered Wood.APAThe Engineered Wood Association.
