It’s easy to confuse marine plywood for exterior plywood. Unless you have a very discerning eye, you won’t be able to tell any physical differences between the two. They also have practically similar uses.
But for experienced builders, there’s a significant difference between marine and exterior plywood. You have to know what these distinctions are to be able to use them appropriately.
What is marine plywood?
Marine plywood is a timber product made from several layers of wood veneers (plies). These sheets are then bonded using water-resistant adhesive known as weather and boil proof (WBP) glue.
Many people consider marine grade plywood as one of the highest qualities of plywood around. Unlike most other plywoods, marine plywood uses a larger number of thinner layers of wood. However, it doesn’t mean that it’s any weaker or less sturdy.
Plywood makers arrange the wood plies in such a manner that they become highly compressed. They also use a special adhesive to bond the layers together. All these methods help give plywood its distinct toughness and damage resistance.
To produce marine plywood, manufacturers use naturally water-resistant tropical hardwood. They choose only the highest quality grade of veneers. This ensures that the resulting plywood doesn’t have any defects. It won’t have core gaps even when you cut the sheets.
Plywood suppliers offer marine plywood in several different grades. Each grade comes with a distinct knot size and frequency. Every one of them also has a unique weight and thickness.
- Medium-density overlay (MDO)
- High-density overlay (HDO)
One of the most common uses of marine plywood is boat building. People use it to make different parts of the boat such as the hull. They take advantage of the plywood’s excellent pliability and water-resistant properties.
It’s not limited to seafaring, of course. Any portion of a house or building exterior can have plywood cladding made of these marine-grade boards. This is useful for construction projects in areas that see lots of rain and fluctuations in temperature.
You can also use marine-grade plywood in commercial settings. Some restaurants and hotels use this plywood for their kitchens and bathrooms. benchtops and cabinets. It helps keep benchtops and cabinets waterproof.
Another example of marine plywood use is as subfloor material. It prevents water and moisture from seeping through it, whether from the surface or below.
Other popular uses of marine grade plywood include:
What is exterior plywood?
Exterior plywood is the general term for weather-proof plywood used primarily for outdoor applications. It is made from several layers of wood veneers bonded together using phenolic resin. The glue hardens to form a crystalline substance, making the plywood more resistant to moisture and humidity.
To make exterior plywood, manufacturers used wood from hoop pine. Other plywood materials include spruce, mahogany, Douglas fir, birch, oak and maple.
They treat the veneers with preservatives to make them more suitable for external use. This allows the plywood to withstand harsh weather conditions such as strong winds and heavy rain.
Similar to other plywood products, exterior plywood also comes in different ratings. Each grade represents the quality of the plywood sheet.
- A (cabinet grade)
- C-D (construction grade)
- X (suitable for outdoor use)
- C-D-X (most common grade)
Most builders use exterior plywood for non-structural, exterior applications. They take advantage of the plywood’s properties to create a high-quality aesthetic finish. Visit any building and you’ll likely see the plywood used for its outdoor walls and ceilings.
But exterior plywood isn’t only limited to outdoor applications. Some builders have used this plywood in interior settings as well. These include storage and refrigerated areas.
Exterior plywood also works great as a subfloor. Its water-resistant nature doesn’t allow moisture to penetrate the floor whether from the surface or below.
Some other interior applications of exterior plywood include:
- Kitchen cabinets
How is marine plywood different from exterior plywood?
One of the main differences between marine plywood and exterior plywood is their adhesives.
Manufacturers use only permanent weather and boil proof glue to make marine plywood.
Meanwhile, they use other types of WBP glue for general exterior plywood.
Marine plywood standards also do not allow for any defects, even on its surface. This ensures that plywood remains water-resistant. On the other hand, exterior plywood allows for some defects. You can typically see this on C-D grade plywood.
The two plywood can differ in their thickness as well. You can find marine grade plywood with a veneer thickness of 1.3mm – 3.8mm for multi-ply construction. It’s also available in 0.5mm thickness for three-ply construction. Exterior plywood can come in reasonably thinner veneers to make them more affordable.
Finally, marine plywood and exterior plywood differ in their species of wood. Manufacturers must use only high-density hardwood to produce marine plywood. Meanwhile, less stringent standards for other exterior plywood allow them to use either high-density hardwood or mixed light hardwood.
How are the two plywoods similar?
Much of the similarities between marine plywood and exterior plywood come in their uses.
Both marine and exterior plywood make excellent subfloor material. Their water-resistant properties prevent moisture from passing through the subfloor and reaching the floor’s surface.
Marine-grade plywood can withstand extreme conditions. Boat makers use it to make their vessels stronger against the constant abuse of the sea. But exterior plywood is no slouch either. It can withstand harsh weather conditions such as strong winds and heavy rain.
There’s no denying that both types of plywood can easily handle the wear and tear of daily use.
Choosing between marine plywood and exterior plywood
As you have found out, marine plywood and exterior plywood may look the same at first glance. However, they have quite a few characteristics that set them apart from each other.
Are you choosing between marine or exterior plywood for your next commercial project? Feel free to contact our experts today for more specific advice.