Is Plywood Waterproof?

Can plywood be waterproofed? Let's find out!

Is Plywood Waterproof? Or Does The Type of Plywood Make a Difference?

As one of the most widely used materials in construction, Plywood can be found in wall and ceiling linings, the exterior of structural projects, and even in marine applications. However, despite its popularity, Plywood that has the A Bond glue is waterproof provided it’s sealed correctly. 

It should be noted, in the vast world of plywood, there are four primary glue types to be aware of:

  1. A Bond – a robust waterproof solution made from phenolic resin.
  2. B Bond – a semi-waterproof glue made of PVA.
  3. C Bond – moisture-resistant but recommended for interior use due to its urea-formaldehyde composition.
  4. D Bond – well, let’s just say it isn’t the strongest link in the chain.

When it comes to Marine, Exterior, Birch, or Structural Plywood you’ll find they all proudly wear the A Bond glueline badge.

Nevertheless, Plywood is quite literally everywhere nowadays, so we can definitely benefit from developing waterproof plywood and making this sturdy material suitable for even more applications.

Today, we’ll be detailing some of the most popular types of plywood, how much water they can withstand and where best to apply these materials.

Article Contents:


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Why is Plywood not Waterproof?

Ironically, the reason why Plywood is not waterproof boils down to the fact that it is not developed with water, it has a moisture content between 8% and 13% which fluctuates with atmospheric conditions.

Should different types of plywood become exposed to too much water, the sheets will expand and subsequently compromise the structural integrity of the Plywood. Excess water exposure can also cause plywood to rot just like any other untreated wood material.

But here is a tip, when using them for external applications, always seal the edges. This keeps the timber from rotting. How do you do that? A coat of Latex Acrylic Undercoat is recommended and does the trick to keep the rot at bay.

Is Plywood Waterproof
Is Marine Plywood Waterproof

Is Marine Plywood Waterproof?

Despite misconceptions, Marine Plywood is not waterproof.

The reason why Marine Plywood is suitable for boats and water-based constructions is due to the use of waterproof sealing glue. Contrary to popular belief, Marine Plywood itself is not treated with chemicals and so, therefore, it is still prone to rotting when exposed to excess water or moisture. Without this waterproof A Bond glue, even sheets of marine-grade Plywood would slowly degrade.

Nevertheless, the risk of this is very low when installed correctly which is why Marine Plywood is often the go-to material for boats.

Is Structural Plywood Waterproof?​

Is Structural Plywood Waterproof?

No, structural plywood is not waterproof.

While Structural plywood is designed to be strong and resilient against water and moisture, it is not considered waterproof.

Structural plywood can be treated to be more water-resistant, making it suitable for some outdoor applications. However, like regular or standard plywood, it’s not immune to the effects of prolonged water exposure. Over time, structural plywood can suffer degradation if not properly protected or if used in applications for which it wasn’t designed.


Is Birch Plywood Waterproof?

No, Birch Plywood is not waterproof.

Just like most other types of Plywoods, Birch Plywood can withstand low levels of moisture, however, it is not waterproof. Without the use of an A Bond glue sealant and when exposed to too much water or moisture, Birch Plywood will often expand and slowly degrade.

As such, Birch Plywood is often used for interiors or in furniture production, with the occasional use case for outdoor furniture when treated with waterproofing materials or sealants.

Can you waterproof Plywood?

As much as there is no type of Plywood that is truly waterproof, it is possible to improve water resistancy and waterproof Plywood to a certain degree by using smart installation techniques and certain types of glues or sealants.

The waterproof nature of plywood depends on its type and the specific requirements of its application. While standard and structural plywood possess some degree of water resistance, only the sealants used in marine-grade plywood are waterproof.

If waterproofing is a critical requirement for your project, it is essential to choose the appropriate type of plywood and take additional measures, such as applying protective coatings, to ensure the longevity and performance of your selected materials.

Understanding the distinct characteristics of different plywood types can help ensure that your next project is built to last. Whether you’re building a boat or constructing an outdoor shed, selecting the right plywood can make all the difference and we’re here to help!


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