What is Plywood?Types, Grades & Best Uses (Complete Guide)

Plywood has been around for centuries, but it hasn’t always been what we know it as today. 

In the modern world, plywood is used for all residential construction projects, including cabinet building, sheds, subfloors, wall panels, and bathroom vanities. However, it was used in ancient Egypt for underground tunnels and minor building work.

Over 2 million cubic meters of the material is sold yearly, and the industry value keeps rising (according to Statistica). Plywood is a fascinating invention; there’s much to learn about the building material.

Please keep reading to learn our top five interesting facts about plywood. 

5 Interesting Plywood Facts

1. Plywood Comes in Grades A-D for Strength, Discoloration, Defects & Moisture Resistance

More than 10 plywood variations exist, including softwood, hardwood, marine-grade, aircraft-grade, and overlaid. 

Each type of plywood has four set grades: A, B, C, or D. The grades depend on the quality of the sheet, the plywood, and the glue used. Higher-quality grades are more expensive than lower grades.

Grade A plywood is the highest quality available. It is strong, has minimal defects/knotholes, is highly water-resistant, and doesn’t discolor easily. 

For this reason, it’s best used for furniture or cabinet doors, particularly in high-humidity areas (like bathrooms or kitchens). Grade D is the lowest quality of plywood and is, therefore, the cheapest. 

2. Each Layer is Rotated 90 Degrees to Prevent Warping & Improve Strength

When plywood is made, and the core layers are bonded together, they aren’t molded in the same direction as natural wood. 

Each layer is purposely rotated 90 degrees before gluing. This makes the wood more potent and more resistant to stress without splitting or warping, which is why it can be used for subfloors.

Likewise, unlike natural solid wood, the change in the direction of the wood grain enables screws or nails to be driven into the wood more easily. 

The varying grain also provides better compression, allowing nails or screws to remain in the sheet. However, despite this, screws are typically better to use in plywood vs nails.

3. Inner Layers are Stronger Than Outer Layers

Plywood is made by compressing thin layers of wood together with heat and glue to produce a reinforced wood sheet. 

When treated and sealed properly (such as with epoxy or polyurethane when used externally), plywood can last up to 35 years, potentially longer when used internally. 

When plywood is constructed, the inner layers are usually made of cheaper wood, while the outer layers are made from stronger, higher-quality wood. 

How strong each ply layer is depends on the sheet’s grade (quality). Higher grades will likely use higher-quality wood for the inner core veneer layers than for the outer layers.

4. How Plywood is Glued Impacts Use

Various types of glue can be used to bond plywood sheets. The most common are urea formaldehyde, melamine, and phenolic glue. 

Most plywood is created with urea formaldehyde. It offers the strongest hold over prolonged periods, which makes plywood last longer. 

This is particularly important when using plywood for subfloors or roof sheathing. Phenolic glue is often added to urea formaldehyde glue to make the boards more waterproof. 

Melamine is not the strongest or most durable type of glue, so it’s often found in cheaper plywood.

5. Plywood Was Invented in 2600 BC by the Ancient Egyptians 

Despite plywood being a modern engineered wood product, it was invented almost 5,000 years ago by the ancient Egyptians. Similar inventions were found in ancient Greece, with scribing depicting the construction process.

Alike today’s processes, plywood was made by manually stripping wood into thin veneer plies and gluing them together to form a bonded plywood sheet. 

Between 1800 and 1900, plywood construction significantly improved. The material became more vigorous and was available in various weights, thicknesses, sizes, and grades. 

Frequently Asked Questions 

What is Special About Plywood?

Plywood is one of the most universally popular materials for interior and exterior construction projects worldwide. According to Statistica, around 2 million cubic meters of plywood are sold every year. 

In the US alone, the plywood market is expected to exceed $15 billion by 2030 (source), with significant growth projected between 2022 and 2030 due to its growing popularity. 

It’s one of the most versatile and affordable wood products on the market, used for both residential and commercial building projects. 

It’s strong, durable, and water-resistant, and comes in various grades and finishes to suit every construction project. It’s also easy to use, cut, paint, stain, and finish. 

Additionally, plywood is widely available in convenience stores across the US and around the world.

What is the Advantage in Using Plywood Material?

Plywood is widely used because of its advantages, which include:

• Strong – Able to withstand heavy weights
• Durable – Can last up to 35 years in most woodworking products
• Water-resistant – Can withstand a high degree of moisture (particularly marine grade plywood)
• Affordable – Costs between $12-$55 per standard sheet, and up to $120 for higher grade/thicker boards

Why is Plywood Used Instead of Wood?

Plywood is a cheaper, stronger, and more widely available wood product compared with solid wood. 

While solid wood is strong, it is heavy, more expensive, and prone to splitting under pressure. It is also less widely available and therefore more expensive than plywood. 

On the flip side, plywood is strengthened, highly versatile, and offers significantly better resistance to brute force. 

How Strong is Plywood?

Sheets of plywood come in varying thicknesses, ranging from ½ inch to 1.5 inches. Its thickness directly corresponds with how strong it is and how much weight the plywood sheet can hold. The type of plywood also affects its durability (hardwood vs. softwood). 

The average plywood sheet can support between 5 and 50 lbs per square foot. Thicker plywood, 1 inch or thicker, can support up to 170 lbs per square foot. Size also matters when it comes to how much weight plywood can bear. 

How Long Does Plywood Last?

Because plywood is engineered to withstand heavy loads and provide structural support, it offers high durability and a long lifespan. Plywood can last up to 35 years, sometimes more. 

When used outside, how long plywood lasts depends on how well it’s treated and the weather conditions. Coated with epoxy or polyurethane, plywood can last for years outside in window frames or outbuildings. If left untreated, sheets are likely to rot within 1-3 years. 

Learn more about how to treat and prevent wood rot in plywood. 

Is Plywood Weak?

Generally, plywood is a strong wood alternative that can be used for almost any residential construction product. This includes heavy-duty reinforcing projects such as wall and roof sheathing, floor leveling, and reinforcing subfloors. 

An average plywood sheet of ¾ thickness can hold up to 50 lbs, depending on its size. 

However, not all plywood is strong enough for structural reinforcement. Small, ¼-inch-thick sheets can only withstand about 5 lbs and are therefore not considered strong.