Plywood is a composite material, it consists of engineered wood veneer sheets glued together under high heat and pressure to form panels. It’s a worldwide multi-use material proven to be effective and adequate for just about any construction job.
To ensure the finished product is as strong as it gets, manufacturers lay each wood sheet using a cross-graining technique, alternating the grain direction between layers of wood to reduce weak spots and make the plywood’s strength consistent across the board.
This manufacturing technique not only allows the user to nail the edges of a panel without compromising its structural integrity, but it also reduces material expansion and shrinkage originated by temperature shifts.
The common size of commercial plywood panels is either 4 feet x 8 feet (covering 32 square feet), or 5 feet x 5 feet (covering 25 square feet).
What is Plywood Used For?
Plywood is used everywhere, from the smallest DYI project to big constructions. Using plywood for residential construction can significantly reduce the time taken to build a house compared to alternative solutions.
Although it’s impossible to pinpoint every use for plywood under one article alone, here are the most relevant uses for plywood:
Exterior Wall Sheathing
The number one use of plywood across the United States. This application of plywood is mainly seen in areas suffering from earthquakes, strong winds, and other extreme weather conditions.
Exterior plywood boards are typically used to strengthen construction frames. They have notorious flexibility and are designed to deal with all sorts of bad weather.
Even though plywood is generally used for structural purposes, there are a few advantages of using it as the surface of interior walls.
Plywood is able to support heavy loads and some types of plywood are moisture-resistant, this means it can handle the hanging of heavy objects (shelves and other heavy fixtures) and some humidity better than other kinds of material such as drywall.
Plywood is often used as roof decking, it’s a great material to support roof shingles. It’s nowadays used as an alternative to plank decking which has fallen out of use.
Plywood is often used mainly as a layer below the main floor but not because it’s not strong enough, it’s simply due to its looks. Even top-quality plywood doesn’t match the solid wood finish.
Different Types of Plywood
There are different types of plywood made with different types of ply (wood veneer layers) and each panel type is best suited for a specific use.
There are panels built for a whole cast of scenarios such as construction, furniture, boats, all the way up to aircraft jobs.
The mainstream types of plywood are:
Among the vast choice available, the most commonly used types of plywood are:
Structural Plywood or Sheathing Plywood
This kind of plywood is designed to be strong, inexpensive, and to last for several decades.
Even though it’s high quality, it’s not often suitable for places where it’s visible due to its unfinished look. It’s mainly used in new construction as sheathing material (typically nailed to the frame structure) and it’s meant to be covered with other materials.
Just like the name hints, hardwood plywood is made of strong types of wood, such as birch, oak, and mahogany.
Sanded hardwood plywood is typically used for cabinets, furniture, and a variety of other “exposed to the eye” projects.
It’s made from trees like pine, spruce, and cedar. Softwood plywood is often found in a wide array of modern construction work.
Exterior plywood is put together with waterproof glue, which makes it the perfect choice for outdoor spaces that are subject to humidity.
Because of its chemical treatment, exterior plywood is able to resist moisture better than some of its alternatives. It can be used for porches, decks, sheds, and other exterior constructions exposed to the elements.
The Different Grades of Plywood
Understanding the different grades of plywood is critical to choose the best kind for the task at hand.
Softwood Plywood Grades
Softwood plywood is rated for quality using two grades for each panel, one grade for the face veneer, and another grade for the back veneer.
There are four applicable grades when it comes to softwood panels: A, B, C, and D.
A-grade – The highest quality wood veneer and therefore the most expensive. A-grade plywood is flawless and easily paintable, perfect for projects that will be visible to the eye.
B-grade – Slightly less smooth, usually has minor flaws that may or may not require minor repairs depending on the intended use.
C-grade – Typically contains some open defects, knots up to 1.5 inches in diameter can be found in its sheets.
D-grade – The cheapest wood veneer there is, contains major flaws, knots up to 2.5 inches are not uncommon in this type of panel.
As mentioned above, the grading system for these panels is measured in pairs, therefore, a “BC” panel would have a b-grade face veneer, and a c-grade back veneer.
Hardwood Plywood Grades
Hardwood plywood’s quality is measured in a slightly different way.
Just like softwood panels, the front veneer is rated with A, B, C, and D grades, but the back sheet’s quality is rated with numbers: 1, 2, 3, and 4. The highest quality grade is 1 and the worst is 4.
Number of Plies in Plywood and its Thickness
Plywood is constituted of three parts, the face veneer, the core, and the back veneer.
In between the face and the back veneer, there are the core layers. These are made of thin layers called plies.
The core purposefully has an odd number of plies which helps reduce warping and deformation. The minimum number of plies in commercial plywood is typically 3, this number can go all the way up to 21 plies.
Regarding plywood thickness, it’s determined by the number of plies its core contains. Some jobs demand thick and sturdier panels and other jobs require thinner and bendable panels.
Here’s a rough relation between the number of plies and the panel’s thickness:
|Thickness (inches)||Number of Plies|
|0.07 ~ 0.1||3|
|0.14||3 to 5|
|0.2 ~ 0.25||5 to 7|
|0.3||7 to 9|
|0.5||9 to 11|
|0.6||11 to 13|
|0.7||13 to 15|
|0.8||15 to 17|
|0.9||17 to 19|
|1||19 to 21|
Advantages of Plywood Over Solid Wood
Cheaper Solid Wood Alternative
Although the highest quality plywood panels will generally be more expensive than solid wood, average projects typically don’t demand the highest quality plywood available.
Comparing both solid wood and plywood from an equality point of view, cheap plywood will generally be cheaper than cheap solid wood, and higher quality plywood will be cheaper than higher quality solid wood.
Large Sizes Available
Solid wood is created by nature and has natural size limitations, plywood is manufactured, therefore it’s available in larger pieces.
If your project calls for large pieces of flat material, plywood is the best choice when it comes to square-foot coverage.
Curved Surface Friendly
Applying solid wood to curved surfaces will most likely produce bad results. Certain types of plywood are specifically made to fit curved surfaces without the risk of rough results, or even breaking.
Better for Fire and Moisture
Solid wood will contract and expand under temperature and humidity changes no matter its quality.
Plywood is engineered and chemically treated, it can be made to be waterproof and/or fire-resistant, surpassing solid wood’s natural capabilities of handling temperature changes.
Plywood is Eco-Friendly
A workable plywood sheet will contain less wood compared to a hypothetical same-sized solid wood sheet.
Besides this, plywood doesn’t release any toxic gases and can be recycled at the end of its usable lifetime.
The Biggest Disadvantages of Plywood
Not as Strong as Solid Wood
Solid wood is homogeneous and plywood is made of wood sheets glued together, solid wood should be stronger in most cases.
Nevertheless, which one is stronger is still debatable as each project and budget will require different solutions.
Doesn’t Last as Much as Solid Wood
Plywood has an incredible lifespan of approximately 30-40 years on average.
This record is easily beaten by quality solid wood though, it lasts for generations if properly cared for.
Commercial plywood used to be made with formaldehyde-based glue back in the day. This particular glue has been linked to several kinds of respiratory illnesses and cancer.
The good news is that nearly 60% of the plywood industry has now abandoned this glue from its production due to Dr. Kaichang Li’s innovative research, a new kind of harmless glue based on soy protein.
There are several alternatives to plywood worth considering such as:
- Oriented Strand Board (OSB)
- Medium Density Fiberboard (MDF)
- High-Density Fiberboard (HDF)
- Polyurethane Board
- EKO Ply
- Solid Wood
These alternatives can be an effective solution if you can’t get your hands on plywood, or if you can find them for cheaper prices.