Exterior Plywood vs. Interior Plywood: Key Differences and Best Uses

Plywood is a versatile and widely used material in construction, furniture making, and DIY projects. When considering plywood for your project, understanding the differences between exterior plywood and interior plywood is essential. These two types of plywood are designed for distinct applications, and choosing the right one can significantly impact the durability, performance, and appearance of your work.

In this blog, we'll explore the differences between exterior and interior plywood, their characteristics, and when to use each type.

What is Plywood?

Plywood is made from thin layers, or plies, of wood veneer that are glued together. The layers are typically arranged with the grain of each layer running perpendicular to the one beneath it, which gives plywood its strength and durability. The number of layers and the type of wood used can vary, making plywood suitable for a wide range of applications.

What is Exterior Plywood?

Exterior plywood, as the name suggests, is specifically designed to withstand outdoor conditions. It is engineered to handle moisture, humidity, and temperature fluctuations without losing its strength or integrity. Exterior plywood is typically used for applications where the material will be exposed to the elements or will come into contact with water.

Key Features of Exterior Plywood:

1. Water-Resistant: The most significant characteristic of exterior plywood is its ability to resist moisture. It is manufactured with waterproof adhesives that prevent the layers from separating or warping when exposed to rain or high humidity.
2. Durability: Exterior plywood is built to endure harsh environmental conditions, including sun, rain, and wind. It's a popular choice for applications like roofing, siding, and outdoor furniture.
3. Types of Exterior Plywood:
   • Marine Plywood: This is a high-quality exterior plywood designed to withstand prolonged exposure to water. It is used in boat building, docks, and other marine applications.
   • Pressure-Treated Plywood: This plywood is chemically treated to resist rot, insects, and fungi. It's ideal for use in applications where the plywood is exposed to soil or moisture, like outdoor decking or landscaping.
   • Exterior Grade Plywood: Standard exterior plywood is made for general outdoor use. It can be used in applications like sheds, barns, or garden structures.

When to Use Exterior Plywood:

• Outdoor Structures: Use exterior plywood for fences, decks, garden sheds, and any other structures exposed to the elements.
• Water-Resistant Projects: If you're building something that will come into direct contact with water (e.g., boat docks or outdoor furniture), marine plywood or treated plywood is ideal.
• Roofing and Siding: Exterior plywood is often used for sheathing roofs and walls in residential and commercial buildings. It can withstand weather conditions while providing a sturdy base for roofing materials or siding.

What is Interior Plywood?

Interior plywood, on the other hand, is designed primarily for indoor use. It is not built to withstand exposure to moisture or extreme temperature changes and should only be used in dry, climate-controlled environments. Interior plywood is often used in furniture making, cabinetry, and interior wall sheathing.

Key Features of Interior Plywood:

1. Not Water-Resistant: Unlike exterior plywood, interior plywood is made with regular adhesives that are not resistant to water. It should never be used in damp or outdoor environments.
2. Smoother Finish: Interior plywood typically has a finer surface finish, making it more suitable for visible applications where aesthetics are important. It’s often used for furniture, cabinetry, and trim work.
3. Variety of Wood Species: Interior plywood comes in a wider variety of wood species and finishes, such as birch, oak, maple, and walnut. These varieties offer different looks and characteristics for furniture-making and decorative applications.
4. Lower Cost: Since interior plywood doesn't need to withstand harsh weather conditions, it is generally less expensive than exterior-grade plywood.

When to Use Interior Plywood:

• Furniture and Cabinets: Interior plywood is ideal for building furniture such as tables, chairs, bookshelves, and cabinets, where it will remain in a controlled indoor environment.
• Wall and Ceiling Paneling: For decorative applications inside the home, such as wall or ceiling paneling, interior plywood can add a rustic or modern touch depending on the wood species chosen.
• Interior Doors and Trim: Interior plywood is commonly used in the production of doors, window frames, and trim work where moisture exposure is minimal.

Key Differences Between Exterior and Interior Plywood

How to Choose Between Exterior and Interior Plywood

Choosing the right type of plywood for your project depends on the environment where the plywood will be used. Here are some tips to help you make the right decision:

• For Outdoor Projects: If your project will be exposed to the elements or high moisture levels (such as outdoor furniture, garden sheds, or roofing), exterior plywood is the best choice. Look for marine or pressure-treated plywood for the best resistance to water and rot.
• For Indoor Projects: For projects inside your home, such as furniture, cabinetry, and interior walls, interior plywood will be sufficient. It's more cost-effective and has a better finish for decorative purposes.
• Consider the Budget: While exterior plywood is more expensive due to its durability and water-resistant properties, it is essential for outdoor use. For indoor applications, interior plywood can save you money without compromising quality.

Conclusion

Understanding the difference between exterior and interior plywood is crucial for ensuring the success of your project. While exterior plywood is built to withstand moisture, temperature changes, and the rigors of outdoor conditions, interior plywood excels in dry, controlled environments and is perfect for decorative and functional indoor applications.

By selecting the right plywood type, you can enhance the longevity and appearance of your project while ensuring that it performs as expected. Whether you're building a weather-resistant outdoor structure or a stylish indoor piece of furniture, knowing when and where to use each type of plywood will lead to the best results.