Exterior Plywood

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Where typical timber and MDF would buckle and fail, exterior plywood prevails. Unlike typical timber products, exterior plywood is a type of engineered wood product that is made from thin layers of preservative and chemical-infused wood veneers that are primed to resist moisture, insects, and other types of environmental damage. These veneers are then bonded together using a high-quality adhesive, such as a waterproof phenol formaldehyde resin. This meticulous process endows exterior plywood with excellent weather-resistant properties and the ability to withstand moisture and humidity. Previously referred to as WBP plywood (WBP standing for Weather and Boil Proof), this terminology has now been superseded by the EN13986 and EN636 classifications. This strong, versatile plywood board is most commonly used in structural and exterior applications such as floors, decks and furniture, provided it is properly sealed.

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What Is Exterior Plywood?

As its name suggests, exterior plywood is a type of plywood that is specially designed for external use.

Engineered to withstand harsh weather conditions and outdoor environments, it is made using high-quality veneers and a waterproof adhesive that ensures it can resist water, moisture, and other environmental factors.

One of the main benefits of exterior plywood is that it can maintain its strength and stability even in wet conditions.

This makes it an ideal choice for external applications that require a high level of durability and resistance to the elements, such as outdoor furniture, sheds, and roofing.

In addition to its weather resistance, exterior plywood is also known for its versatility and ease of use.

It can be cut and shaped to fit any project, and it's available in a variety of thicknesses and sizes to accommodate a wide range of needs.

Exterior Plywood Key Features

  • Purposed for outdoor use in demanding applications
  • Precision manufacturing process prevents warping
  • Can be painted or clear finished
  • Manufactured from multiple layers of thin veneer that are glued together
  • Maintains its strength and stability even in wet conditions
  • Perfect for creating long-lasting outdoor projects
  • Perfectly suited for structural tasks where occasional wetting may occur

Types of Exterior Plywood

When it comes to exterior plywood, there are a variety of types to choose from, with CDX and ACX being the most common. The X marking on the plywood denotes its use as exterior plywood, with the first two letters indicating the construction grade. A denotes a premium grade that is used for higher-end applications, while CDX is a more affordable construction grade option that is still sturdy and durable.

Exterior plywood can be made from a variety of materials, including veneers, high-density hardwood, or light hardwood.

With so many options to choose from, it's important to select the right type of exterior plywood for your specific needs.

Whether you're building a boat, outdoor furniture, or a shed, understanding the various grades and materials available will help you choose the best option for your project.

Marine Plywood

Marine plywood is the highest quality option, comprising a knot-free structure. The only plywood on the market to be employed nautically, this highly durable plywood is engineered with waterproof glue making it simply unrivalled when it comes to resisting water damage and rot.

To give you an idea of its durability, marine plywood is specifically optimised for submersion in water as part of a boat's hull.

Hardwood Plywood

Depending on the grade and treatment used, hardwood plywood can be applied externally in humid conditions as well as in interior applications.

When applying the sheets externally, ensure their longevity and moisture resistance by using the correct type of edge sealant.

One of the most crucial steps when waterproofing plywood is to ensure that you seal the board's edges properly. This step is essential to protect the board.

Our hardwood structural plywood can be used for exterior and interior applications, provided it is sealed correctly. 

Other Types of Exterior Plywood

Other types of exterior plywood include pressure-treated plywood, overlaid plywood, and oriented strand board (OSB).

Pressure-treated plywood is infused with chemicals that increase its resistance to mould and mildew, while overlaid plywood has a cleaner finish that is more attractive and holds up better against wear and tear.

OSB is an engineered substitute that is best suited for semi-exposed areas.

We stock regular plywood, birch plywood and several other plywood sheet materials suitable for interior and exterior use in roofing, flooring and exterior wall sheathing applications. Browse our full selection of plywood sizes and types on our plywood homepage.

Frequently Asked Exterior Plywood Questions

How Is Exterior Plywood Graded?

Exterior plywood is marked with an "X" to denote its intended use, and the construction grade is indicated by the first two letters of the label.

"A" grade is the highest quality and is used for high-end applications, while "CDX" grade is a more affordable, construction-grade option that's still sturdy and reliable.

What Are The Different Types of Plywood Grades? 

Plywood is graded into 4 primary groups:

  • Class 1 – Strictly internal
  • Class 2 – Interior grade of humid conditions but must be sealed
  • Class 3 – Exterior grade but must be sealed (outdoor use)
  • BS10 88 – Marine Plywood

What Is Cross Graining? 

Hardwood plywood is an engineered wood composed of cross-grained thinly sliced wood veneers. 

Cross-graining is the practice of orienting the wood grain of each plywood layer at right angles to the one below it. This alternating criss-cross pattern is behind plywood's impeccable strength and rigidity.

There are a few key reasons why cross-graining is so integral to plywood's overall strength: 

  1. It helps to distribute weight more evenly across the surface of the material. This is because each layer is supporting the one above it, rather than all the weight being concentrated in one area.

  2. Cross-graining makes plywood less likely to warp or deform over time. When all the grain is going in the same direction, it is easier for the plywood to bow or twist out of shape. But when the grain is alternating, it prevents warping, making it much more difficult for the plywood to deform.

  3. Cross-graining gives plywood added strength in both tension and compression. This means that it can withstand more force without breaking or sagging.

What Is WBP Plywood? 

The term "WBP Plywood" (which stands for "Weather and Boil Proof") refers to the type of glue that is used to bond the layers of wood veneer together.

This terminology has been superseded by the EN314 and EN636 classifications, which define the bonding quality of the adhesive and the standards to which the plywood will perform. 

All of our general-use hardwood birch plywood sheet materials (made from birch veneers) meet level 2 under these classifications, which means that they are suitable for use in humid conditions, and can be used outside if treated with an appropriate preserver and sealer.

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