What Is Marine-Grade Plywood?

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Discover The Popular Plywood Choice: Marine-Grade

Marine plywood, often called simply marine plywood, is not what is often claimed. That is, it is not waterproof. It is a good quality hardwood plywood made with waterproof glue, but since it is not treated with chemicals, it is not rot-resistant. The best grades also tend to be light, strong, and virtually flawless.

These qualities make this plywood a popular choice for building boats and their parts. It is also a smart choice for durable outdoor furniture projects in coastal areas, especially after receiving a strong protective finish.

What is marine-grade plywood?

Marine-grade plywood is a specially designed panel made from Douglas Fir or Western Larch in accordance with APA: The Engineered Wood Association. All layers may have knots but not knots.

Marine plywood is available in the following grades:

  • A-A
  • A-B
  • B-B
  • Medium Density Overlay (MDO)
  • High-Density Overlay (HDO)

Other hardwoods

Wood species with natural resistance to decay, such as redwood, cedar, ipe, edging, and cypress, have a natural resistance to decay. Marine plywood is not pressure-treated to resist degradation like pressure-treated lumber and plywood. This means that if the marine plywood is exposed to moisture, it must be protected with a good waterproof finish. If you need a material that will resist moisture without a protective finish, choose pressure-treated wood or plywood rated for the expected level of exposure.

What makes it strong?

Thin sheets of wood veneer, known as layers (plural of sheets), are used to make plywood. The arrangement of the sheets in perpendicular layers is what makes the plywood stronger. According to the APA, each piece of plywood has an odd number of layers. Cross lamination, the arrangement of the layers perpendicular to each other, is what gives the panel strength in both directions. Finally, the plywood panel is glued under heat and pressure.

Why waterproof glue?

The main benefit of using waterproof glue on marine plywood is that if the plywood is exposed to moisture, or even very high humidity or boiling temperatures, the glue will not fail and therefore the plywood layers will not delaminate or crumble. This is an important design feature if you are building a plywood boat hull. If the protective finish of the hull is damaged and the wood gets wet, the plywood will remain structurally intact.

Plywood Becomes Popular

In 1934 a waterproof adhesive was invented, which paved the way for plywood and its potential. Ships and barracks during World War II were made of plywood. In the postwar building boom, plywood was used to build houses and cities in the United States. By 1954, the industry had grown to more than 100 factories and production was approaching 4 billion square feet, according to the APA.

Good Plywood is different

Although the plywood products sold by most hardware stores are rated A, B, C, and D (with A being the best), they are not considered as high quality as marine plywood and other types of lumber. Standard plywood is made with fewer thicker layers and contains mostly softwood such as Douglas pine or pine. The inner layers also have gaps or holes that you can't see until you cut the plywood panel. Marine plywood is a type of hardwood plywood. Real wood plywood is made from thin layers of 100% hardwood, which is generally stronger and harder and has a finer grain than softwood.

Plywood sold as "void-free" has no hidden voids in the wood layers. When it comes to coats, many thin coats are better than fewer thick coats because thinner coats result in a stronger, denser panel with edges that cut and clean the sand.

Patio Furniture and Outdoor structures

Experienced workers and carpenters use marine plywood for various outdoor projects, including:

  • Garden furniture such as tables, chairs, and benches
  • Covers
  • Porches
  • Chucks
  • Pergolas
  • Planters

We hope you enjoy watching this video about Marine Plywoods

Source: Roberts Plywood Co

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