When it comes to roof and wall sheathing and subflooring and underlayment, both oriented strand board (OSB) and plywood offer unique benefits. However, it is important to understand the key differences between these two products before selecting one for your next project.
OSB has grown in popularity as a cheaper alternative to plywood for sheathing and floor work. But does it hold up to the test of time?
Table of Contents
Cost
When it comes to sheathing and subflooring, both OSB and plywood are good choices for home construction. However, several differences between the two materials can affect a project’s final results. These differences are the main reason that some builders may choose one material over another.
OSB, which stands for oriented strand board, is an engineered wood product that has taken over a significant portion of the sheathing market from plywood in recent years. It is made from small wood strands that are compressed tightly together with glue or resin under heat and pressure. It is considered to be more environmentally friendly than plywood because it uses smaller-diameter trees that can be grown more quickly and harvested from sustainable forests.
Another advantage of OSB is that it tends to be less expensive than plywood. While the exact cost can vary by region and supply, this is generally a fact that many builders appreciate. This lower cost makes it a great option for projects where budget is important.
The biggest disadvantage of OSB is that it can be less durable than plywood. While this is not a big problem in most situations, it can be an issue if the sheathing is exposed to moisture. Unlike plywood, which is resistant to moisture, OSB will absorb water and swell. While this will not usually cause any structural problems, it can make nailing or screwing difficult.
In addition, OSB can also be more flexible than plywood, which can be an issue if the sheathing is being used as a subfloor. This flexibility can lead to bouncy floors, which may not be ideal for homes with tile or hardwood flooring. In this case, it may be better to use a thicker sheet of OSB or consider using a different material altogether.
While both OSB and plywood have their pros and cons, the latter generally provides better performance in terms of resistance to moisture. Plywood can withstand more moisture than OSB and can also be treated to provide even greater protection. For example, Georgia-Pacific offers a plywood product called Plytanium DryPly that is treated to reduce moisture absorption by up to 40 percent. This can help prevent problems such as delamination, edge swelling, and joint sanding that can occur when sheathing is exposed to moisture for extended periods.
Durability
As OSB has overtaken plywood in the sheathing market, it’s important to understand the differences between these two building materials. OSB is made of compressed wood strands that are bonded with adhesives, and it’s typically less expensive than plywood. While it’s cheaper, it isn’t as durable and may not last as long. Conversely, Plywood is a stronger and more attractive material that is better for sheathing and can resist moisture.
The durability of OSB depends on the type of wood used and the manufacturing process. OSB that uses more western softwoods has greater decay resistance but can still rot in the long term. As with other wood products, evaluating the environment in which it will be installed is as important as determining whether the material is suitable.
For example, if you live in an area with frequent rain and high humidity, consider how moisture will affect the product. Moisture can cause the sheathing to deteriorate, and it could result in the need for more maintenance over time. OSB sheathing also has a lower impact resistance than plywood, which means it can’t hold up well against forktine impacts and sharp blows.
Ultimately, it’s up to the individual builder to decide what material is best for their project. Builders should consider their location, the environment, and the cost and appearance of each material.
Plywood is available in many variants, including low-emitting and formaldehyde-free options. It’s a more sustainable option since it uses wood from renewable sources and can be produced using fewer resources than conventional lumber. It’s also a more attractive choice for sheathing, as it has a smoother surface that can be painted or stained. Plywood is also more resistant to water, as it doesn’t swell when exposed to moisture. It also curves well, making it a popular choice for eyebrow windows and similar projects that require curved sheathing. It’s also not as heavy as OSB, which can be a benefit for small construction crews. For these reasons, some builders prefer to use plywood as sheathing in their projects.
Water Resistance
Both plywood and OSB are panel products made from wood, but that’s pretty much where the similarities end. While they both are produced by compressing and gluing pieces of wood together, the way they react to water is a big difference-maker.
Plywood absorbs and dries more easily than OSB, which tends to swell like a sponge and becomes difficult to work with once saturated. This swelling and soaking up of moisture is the biggest reason that builders are hesitant to use OSB. It’s not as strong as when dry, and it takes a very long time to dry out after exposure to the elements.
The good news is that there are a few things you can do to protect yourself from this problem. First, you should only purchase OSB that’s specifically labeled as either grade 3 or grade 4. These specific grades of OSB can resist moisture and hold up in a humid environment.
You’ll also want to apply a waterproof sealant or paint to the surface of the sheathing before you start your project. This will help to prevent moisture from penetrating the board and ruining your job.
OSB does perform better than plywood when it comes to shear strength, but it doesn’t have the same impact resistance. This is a huge deal because houses do undergo significant impacts during severe weather events and even from heavy items dropped onto the floors of a home.
Plywood is more impact-resistant than OSB because it’s constructed from multiple layers of wood veneers, with the grain direction of each ply alternating at different angles to one another. This construction helps to keep the wood from warping or twisting, which would make it less resilient to damage. On the other hand, OSB is constructed from strands of wood that are glued and compressed together to form a solid piece of sheathing. Despite this, it doesn’t fare as well in impact testing. This is why most builders still prefer to stick with plywood when it comes to sheathing.
Appearance
The most obvious difference between OSB and plywood is that while both materials are created by compressing and gluing wood strands together, that’s where the similarities end. The two products are used for similar purposes, such as roof and wall sheathing or subflooring and underlayment, but they offer unique features that make them suitable for different situations.
Plywood is a manufactured wood product that’s typically pressed with urethane or resin under high heat. It consists of glued veneer sheets, called plies, which are configured in an alternating pattern and then compressed. This design creates a stronger and more durable product than solid wood, and it’s also resistant to the expansion and contraction that affects solid wood.
While plywood is durable and affordable, it does have some drawbacks. For example, it’s not as water-resistant as OSB and can delaminate if exposed to moisture or extreme heat. Additionally, it’s not as strong as OSB and can be susceptible to warping.
Oriented strand board (OSB) is an alternative to plywood that’s becoming more popular in the construction industry. While both OSB and plywood are engineered wood products that can be used for sheathing, OSB is more eco-friendly because it’s made from smaller-diameter trees and can be produced with less formaldehyde than plywood. Additionally, it’s available without formaldehyde and in chemical-free versions for those who want to be more environmentally conscious.
OSB is also more affordable than plywood, and it’s generally considered a better choice for roofing and siding because it can handle a variety of weather conditions. It also withstands bending and sagging under heavy loads, making it ideal for steep-slope roofs. However, like plywood, it’s not as attractive for sheathing and will need to be covered with a shingle or other material.
In addition to being more impact-resistant than OSB, plywood is more stable and has greater nail withdrawal strength, which makes it a more durable option for use as a subfloor. It’s also better at absorbing moisture than OSB, which swells and can absorb water if it becomes saturated. Additionally, plywood curves more easily than OSB and is often used for curved projects like eyebrow windows.
