When it comes to subfloor materials, you have two primary choices: Plywood vs. OSB (oriented strand board). While both materials are considered acceptable as far as building codes go, there are many differences between them, so you’ll want to familiarize yourself before starting any project involving a subfloor.
Plywood was the industry standard for subfloor construction for many decades, but with the introduction of lower-priced OSB, many builders shifted over to this newer material. This had more to do with the lower price of OSB than any of its inherent qualities, so it’s not an indication of OSB’s superiority.
Let’s a closer look at Plywood vs. OSB as far as subfloor construction goes, so you’ll have a better idea of which one is the better choice for you.
Plywood is made from multiple layers of wood veneer which are glued together with their wood grains rotated up to 90 degrees in between each layer. This is known as cross-graining and is helpful for reducing expansion and contraction by increasing the dimensional stability of the plywood.Plywood comes in an enormous number of varieties including softwood, hardwood, moisture-resistant, pressure-treated, and fire-retardant. When it comes to subfloors, the most common plywood used is ½-inch to ¾-inch sheets measuring 4’ x 8’ or 4’ x 12’.
Plywood designed specifically for subfloors often features tongue and groove edges that interlock into one another to create a solid bond. It is prominent in a variety of structural applications and is capable of full weather and moisture exposure.
OSB – which stands for Oriented Strand Board – is a material made from large, flat wood chips compressed and bonded together with wax and resin adhesives. The layers are created by shredding the wood into strips which are then formed into layers and combined with resin and then heated to activate the resin.
OSB is cheaper than plywood due to its usage of wood scraps as its primary material and is also more uniform than plywood due to the uniformity of the manufacturing process. Both of these factors contribute to OSB being increasingly popular in the North American structural panel market – commanding 66% of the structural panel market.
OSB used for subfloors typically has tongue and groove edges designed to make installation smooth and straightforward.
OSB vs. Plywood
When you’re building a subfloor, there are a few key differences you’ll need to be aware of when comparing OSB vs. Plywood.
When it comes to uniformity or consistency of the final product, OSB is the clear winner.Because plywood uses actual wood veneers, it can sometimes have large knots or other imperfections that result in a less uniform final product. OSB doesn’t have these same issues, as the manufacturing process results in a highly dense and uniform final product.
When it comes to moisture resistance, plywood is the clear winner. It dries significantly faster than OSB, as it is closer to actual lumber, whereas when OSB is allowed to absorb moisture it takes significantly longer to dry out completely.
It should be said that OSB takes longer to actually absorb water than plywood, but once it does, it’s a more serious issue.
This can be an issue during the construction process, as OSB left unprotected in an open area will absorb moisture and rot if too much moisture is allowed into it.
While material costs do vary by region and time, OSB is generally cheaper than plywood by a significant margin. This is due to a number of factors, including the manufacturing process, and also depends on the specific species of plywood you’re talking about.
While the exact cost difference will vary depending on your region, plywood will run you about 20% to 25% more than OSB. This may not sound like all that much, but it can add up quickly when you’re talking about building an entire house.
Delamination refers to the process of failure when a material fractures into separate layers. This can be a serious issue with plywood, particularly when it absorbs moisture repeatedly. It can also happen to a degree when it comes to OSB, although it’s less likely due to OSB’s construction.
OSB tends to swell at its edges instead of delaminating, which can be a major issue in its own right. While delamination can cause the edges of a plywood piece to come apart, it will still retain its structural integrity once it dries out. Edge swelling on the other hand is a more serious issue, as it will continue to remain even after the OSB board dries out.
Plywood is inherently a stiffer material with greater overall strength. It is about 10% stiffer than comparable OSB, so it results in a stronger and more durable subfloor.
Plywood is the superior option when it comes to durability as well.
This is due to its superior moisture resistance, faster drying, greater stiffness, and better overall strength. These qualities also make plywood the superior choice when you’re building a subfloor under tile or ceramic.
Because of this, discerning homebuyers will often prefer plywood to OSB when purchasing a house.
Ease of Installation
When it comes to the ease of working with and installing OSB vs plywood, I’d have to give the edge to plywood. It’s easier to work with than OSB as it’s less likely to splinter and chip, is lighter, and is suitable for a wider variety of applications than OSB.
Both plywood and OSB are available in a wide variety of sizes and thicknesses, so there is no clear winner here. Keep in mind that OSB is denser and heavier than comparable-sized plywood, so actually working with it is more labor intensive.
Fastener withdrawal refers to the force needed to withdraw a fastener from a given material – in other words, how well it can hold a nail or screw in place.
Plywood outperforms OSB in this regard, meaning it will have a stronger hold on fasteners. This means fewer fasteners are required during installation – which makes the installation process faster and easier.
While all plywood and OSB are manufactured slightly differently, generally speaking, OSB is considered more sustainable than plywoods. OSB uses small fast, growing trees for its wood component, while plywood is typically made from softwood lumber like Douglass fir, spruce, pine, or fir.
While subfloors can be constructed from basic plywood or OSB, there are also several premium tier products that are specifically formulated for use in subfloor construction. As far as plywood is concerned, there are enhanced plywood products made with enhanced water resistance and protective coatings designed to shield the wood from water damage during construction.
As far as OSB goes, the most well-known premium product is Advantech from Huberwood. This stuff is far more durable and moisture resistant than either typical OSB or plywood, and packs features like integrated tongue and groove edges, enhanced stiffness, weight-bearing, and even a 50-year manufacturer’s warranty. All of these features come at an added cost though, with Advantech costing about double what typical plywood does.
Featured image source.