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Plywood Strengths: Choosing the Right Type for Your Project

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There are over 50 different types of plywood out there, all with their designated strengths and weaknesses.

The number of choices can make choosing the best type for your project a confusing decision, especially if you need a plywood that is sure to be strong and able to stand the test of time.

What is the strongest type of plywood?

The strongest kinds of plywood include hardwood plywood, marine plywood, aircraft plywood, and structural plywood. These plywood are suited for heavy-duty construction and structural purposes. Slightly weaker types include exterior plywood and overlaid plywood.

Read on to learn more about these plywood types as well as how to choose the right plywood for your project. 

Plywood Strengths Explained

The strength of plywood depends on many factors, including thickness, layer count, wood species, and even grain direction. 

Soft plywood can be as strong as hardwood plywood under certain circumstances. In general, though, here’s how the types of plywood compare to each other on a scale of one to five with five being the strongest. 

Plywood Strength Chart

Plywood TypeStrength RatingApplications
Softwood3Flooring, walls, subroofing, packaging, and light construction
Hardwood4Cabinets, doors, paneling, toys, musical instruments, architectural design
Exterior4Outdoor structures and furniture (outdoor shelving, planters, gazebo, etc.)
Overlaid4Exterior sidings, concrete forming, industrial containers
Structural5Roof bracing, plywood flooring, walls, internal support structures
Marine5Indoor and outdoor furniture, boat construction
Aircraft5Aircraft, model airplanes, boats, furniture
Lumber Core3Shelving, cabinets

Types of Plywood

Here are some of the most common types of plywood: 

Softwood Plywood

Softwood ply is mainly used in the construction industry to add some structure in subflooring, roof sheathing, and exterior frame sheathing. 

It’s not the strongest material out there—it bends quite easily and is prone to surface cracks—but it’s affordable and versatile, making it a DIY’s go-to ply option. 

Hardwood Plywood

Hardwood plywood is made out of hardwood such as oak, maple, walnut, poplar, and birch. It has between three and seven layers glued at right angles to create a strong base. 

This type of plywood is popular in furniture, musical instruments, sporting equipment, and other projects that require durable structures, like walls, floors, and doors. 

Unlike softwood ply, hardwood ply doesn’t twist, shrink, or warp with age. It has excellent damage resistance and a high strength-to-weight ratio.

Exterior Plywood

Used for outdoor purposes, exterior plywood is made stronger by adhering its layers with water- and weather-resistant glue. 

This makes them a suitable choice for structures and furniture that are constantly exposed to sunlight, rain, humidity, and snow. 

Overlaid Plywood 

Available in medium density (MDO) or high density (HDO), overlaid plywood has an overlaid face with a smooth, finished exterior. 

Despite that, it’s rarely used for decorative purposes; it’s instead more suited for demanding applications like exterior siding, concrete forming, industrial containers, and other projects that require tough building materials. 

HDO panels contain quite a bit more resin than MDO panels, making them stronger and more durable.

It also features a smooth, “steel-form” finish that many find attractive as opposed to MDO’s matte finish. 

Structural Plywood

Structural plywood, also dubbed sheathing plywood, is used to create structural support in buildings, homes, and construction.

It’s one of the most versatile types of plywood out there, valued for its high strength and low price. 

That said, structural plywood isn’t known for its aesthetics. It’s mostly available in untreated panels, and although treated variants are available, it’s not as easily accessible. 

Marine Plywood

Marine plywood, also known as marine-grade plywood, is manufactured with water-resistant exterior glue to help it stand up to moderate moisture. 

It isn’t entirely waterproof, and since it’s not treated with chemicals, it isn’t rot resistant either, but it does a fantastic job of repelling moisture in certain conditions.

For this reason, it’s a popular choice for outdoor furniture and boat construction.

Aircraft Plywood

Due to its sheer strength and build quality, aircraft plywood is one of the most expensive types of plywood available.

It’s made with high-quality hardwoods like birch, spruce, and mahogany, bonded together to create boards that are both heat and moisture resistant. 

True to its name, aircraft plywood is used in the construction of airplanes, fighter aircraft, and air-assault gliders. It’s also used in boats, buildings, and furniture that hold heavy weights for extended periods. 

Lumber Core Plywood

Lumber core plywood, also known as blockboard in most parts of Europe, is made of thick strips of hardwood that are glued into a large panel and two thin veneers. 

It’s not as heavy as hardwood ply but just as stiff, especially over longer lengths.

As such, it’s the best option for bookcases and shelves as well as marine and aerospace applications where weight is a concern. 

Grades of Plywood

When shopping around for plywood, you’ll likely encounter plywood of multiple alphabetical ratings. Some even have two ratings, with an “A” face and a “D” back for example. 

Here’s what they mean: 

  • A-Grade: Highest quality plywood available with little to no imperfections and generally free of defects and small knots. Good for decorative furniture, cabinets, and doors. 
  • B-Grade: Second-highest quality available, sanded smooth but not perfect. May have a few imperfections that need to be repaired with wood filler or patches but overall decent quality. 
  • C-Grade: Unsanded. Good for subflooring, roof sheathing, and other applications where it won’t be seen. Imperfections may require filling and patching. 
  • D-Grade: Unsanded. Also good for applications where it won’t be seen. It has knot holes of up to 2 ½ inches as opposed to C-grade’s 1 ½ inches. Contains many voids, repairs, and knotholes. 

Plywood Ratings

Plywood comes in five major ratings that dictate how they’re meant to be used: Interior, Exterior, Exposure 1, Exposure 2, and Structural 1. 

  • Interior: For indoor use only, water resistant but not waterproof. 
  • Exterior: Suitable for both indoor and outdoor use, waterproofed and can withstand harsh weather climates. 
  • Exposure 1: Waterproofed but can’t withstand long-term exposure after construction. 
  • Exposure 2: Water resistant, can withstand occasional moisture. 
  • Structural 1: Designed for seismic retrofitting, can withstand earthquakes and other seismic activities. 

Types of Ply

Plywood comes in three-ply, five-ply, or multi-ply variations. 

Three-ply is made of three bonded layers. It’s the most common and aesthetically pleasing plywood variant. 

Five-ply is made of five bonded layers and thus is much stronger than three-ply. It can be used in furniture and other projects that require tough plywood. 

Multi-ply is made of up to 12 layers. Each layer is firmly glued together and placed under immense pressure to create a single solid structure. It’s used in exterior projects, like roofing and building construction. 

How To Choose the Right Plywood

When choosing plywood for a project, it’s important to understand the different types of plywood available.

Each plywood comes with its own functions and features, so choose the plywood according to its intended use. 

If you’re planning to use it on exterior projects, like roofing or outdoor furniture, choose suitable exterior plywood. If you’re using it for decorative purposes, A-Grade softwood works perfectly. 

You should also consider the strength of the plywood. If your project requires heavy-duty ply, get a multi-ply variant.

If the plywood won’t carry heavy weights over extended periods, three-ply works just fine. 

Best Plywood for Furniture

When choosing plywood for furniture, make sure it’s MR (moisture resistant), BWR (boiling-water resistant), and BWP (boiling-water proof) to guarantee its durability. 

For this reason, the best plywood for furniture is hardwood plywood and marine plywood. 

Best Plywood for Shelves

The best plywood for shelves is by far lumber core plywood because it’s stiff and durable over longer lengths. 

Best Plywood for Cabinets

For cabinets, always choose A-grade hardwood or marine plywood because they both have a smooth, near-perfect surface that can be painted over. 

Best Plywood for Staining

Plywood made of cedar, birch, and oak are the best plywood for staining. They all have large pores that hold a stain easily and beautifully. 

Best Plywood for Flooring

For surface flooring, marine plywood is the recommended choice. It’s durable and water-resistant, making it suitable for basements, kitchens, and bathrooms. 

For subflooring, you can use softwood, structural, or overlaid plywood of the C-grade category.  

Related Questions:

Is Plywood Waterproof?

Plywood isn’t usually waterproof. Some are considered water resistant, but even the water-resistant ones don’t stand up to moisture very well, especially under prolonged exposure. 
If you want waterproof plywood, search for a variant with the WBP (Water Boiled Proof) tag. WBP plywood is suited for humid environments and extreme temperatures. 

What’s the Cheapest Way To Waterproof Plywood?

Some of the cheapest ways to waterproof plywood include sealing it with epoxy sealer, drying oil, waterproof varnish, or water-based paint. 
These options cost no more than $50 a bottle/can and can greatly extend the life of your plywood during the rainy season. 

Conclusion 

The strongest types of plywood include hardwood plywood, marine plywood, structural plywood, and aircraft plywood.

Each of these variants has its own specific functions from furniture crafting to subflooring. Always choose the plywood material as per your project. 

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