Subflooring is the lowest element of a floor. The floor joists sit on top of the subflooring structure, and then the actual floor sits on top of the underlayment. Usually, a subfloor will be constructed out of either plywood or OSB, but which material is better?
While both plywood and OSB are treated as equally permissible by most building codes, the majority of engineers and contractors agree that plywood is the best material to use for subflooring due to its smooth surface and versatility.
While subfloors are not required by code for construction, they provide an additional element of stability to the floor, which many architects, contractors, and homeowners find appealing.
Keep reading to learn more about what materials are best to use for subfloors, along with some extra information about when and why subfloors are warranted.
What Makes Good Subflooring?
Subflooring plays an important role in the structural credibility of the house. While lack of subflooring is not going to bring the house crashing down about your ankles, the presence of a structural element underneath the floor joists can help to hold them tightly together.
A good subfloor must be made of large, sturdy pieces of material. You want a piece of plywood or OSB with the largest possible surface area so you can unite as many of the floor joists as you can in one piece. This makes the joists tighter and reduces the chance of creaking or loose floorboards.
The panels of a well-crafted subfloor ought to be laid in a staggering brick pattern. Like with brick and mortar, you don’t want the edges of your composite board panels to line up with each other. Staggering the panels will create a stronger overall subfloor, leading to better results and higher floor stability.
What’s the Difference Between Plywood and OSB Subflooring?
Plywood and OSB are, in fact, rather similar materials. Both are composite wood materials, which means they are made from small, thin pieces of wood layered on top of each other and condensed into one panel.
The main difference between plywood and OSB results from their manufacturing process. OSB is made from layers of small wooden strips crossed over each other, while plywood traditionally uses larger chips and presses them together into shape.
Because of the differences in the manufacturing process, there are several key differences that make plywood panels widely popular as the best material for constructing a subflooring structure.
Since subfloors are not required by the building code, there is no official regulation on whether you use plywood or OSB panels in your subfloor structure.
NOTE: OSB is frequently confused with particleboard. Don’t be fooled; they’re not the same. OSB is a structural material, while particleboard is not. To avoid confusion, it may be easier to simply use plywood. Do not use particle board to construct a subfloor structure!
What Are the Pros and Cons of Plywood?
Here are the pros and cons of plywood at a glance:
Plywood is a strong, durable, smooth material that has a wide variety of possible applications. This versatility makes plywood a favorite for subfloors and many other structural projects.
Different Plywood ratings and its usage
Not all plywood is created equally. Plywood comes in grades, ranging from A through D, followed by X.
The highest quality plywood, as one might expect, is grade A. Grade A panels are guaranteed to have little or no blemishes, knots, or flaws. The quality of wood decreases with each grade after that, concluding X-grade plywood.
X-grade panels are essentially scraped wood. However, this does not mean that they’re garbage. Many flooring experts will confirm that X-grade plywood, while unattractive and often riddled with knots, serves its purpose of supporting the floor joists just as well as higher-grade plywoods and even better than some OSB panels.
You do not necessarily need to buy the highest (and therefore more expensive) grade of plywood.
For subflooring structures, which aren’t going to be seen and serve only a practical, utilitarian function, C and D grade plywood should be fine. X grade plywood, though it can technically be used to create a structurally sound subfloor, is not recommended.
The higher grades of plywood are typically reserved for projects such as shelves and cabinets, where the material is more likely to be seen and requires aesthetic finishing.
Although the pricing, sizes, and uniform regularity of OSB have enticed many American contractors in recent years, the qualities of traditional CDX plywood have held it firmly in a position of favoritism as a subflooring structural material.
What Are the Pros and Cons of OSB?
The following table shows an overview of the pros and cons of OSB.
OSB, in the context of building and lumber, is short for “Oriented Strand Board.” The name refers to the way in which this material is constructed, being made from long strips of wood woven together and pressed. The strips are then bonded together with adhesive resin, leaving the final product.
Despite being a relatively modern innovation, OSB overtook plywood in overall popularity as of the year 2000, according to Nachi. Being made from strips rather than random, organically shaped chunks as are used to make plywood, OSB panels are recognized in the construction industry as being more consistently uniform than plywood. The linear composition of OSB also allows for larger panels.
The advanced manufacturing that leads to the creation of OSB also allows for the material to be made at a lower manufacturing cost. These savings are passed down to the consumer, making OSB a generally more affordable material. This makes OSB an especially attractive option for builders and contractors motivated either by budget or profit.
On average, builders can save roughly $600-$800 per 2,000 square feet (185.8061 sq m) by choosing OSB material instead of traditional plywood. Keep in mind, however, that those figures are likely to vary depending on lumber prices, location, quality grade, demand, and other pricing variables.
Both composite wood, though how they are made is different. Plywood uses heat-pressed glue and wood, whereas long OSB uses longer strips of wood woven together and pressed.
NOTE: The manufacturing differences between plywood and OSB also leave plywood the superior option when it comes to withstanding water damage. The lattice-woven structure of OSB composite panels makes them at higher risk from water than its tongue-and-groove plywood counterpart.
Why Are Subfloors Important?
While not absolutely essential to the structural integrity of the building, there are many advantages to including a subflooring element when building.
1. Boosts Overall Structural Stability
The main reason why builders and contractors often decide to include a subfloor is that they increase the overall structural stability of the building. By providing a smooth, solid base, subfloor structures can help keep floors in good repair over a long period of time.
2. Reduces Creaky Floors
By keeping the floor joists tightly together, the presence of a subfloor element underneath the natural floor can keep floorboards from coming loose. Aside from being a point on the side of safety and comfort, this can also reduce the presence of creaky floorboards and other annoyances that arise from an unstable floor.
3. Provides a Work Platform
Another advantage of including a subfloor structure in your building plans is that a subfloor provides a natural platform for workers while the floor is still under construction. It goes without saying that it’s easier to maintain clean tools and keep track of dropped screws, pencils, and nails when you’re working on a solid platform.
4. Prevents Cracked Tiles
If you are building a tile floor—as in a kitchen or bathroom, for example—subfloor structures are a good way to forestall natural damage from wear-and-tear. Tiles crack over time from the constant weight and strain of people walking over them.
While the addition of a subfloor structural element will not completely prevent tiles from breaking and cracking eventually, it can assist joists and underlayment. This ensures, to the extent that it is realistically possible, that the weight of a pedestrian overhead will be evenly distributed across the tile’s surface, reducing the probability of structural damage.
When and Where Should You Build or Repair a Subfloor?
Not every structure requires a subfloor in order to be sound (that’s why it’s not essential in most building codes). However, under certain circumstances—such as tile floors or areas prone to flooding—the presence of a subfloor can help the overall structure remain ship-shape for a long time.
Here are some examples of floors and structures that benefit from a subfloor:
- Basements (if not concrete foundation)
- Rooms with linoleum or hardwood floors
If your subfloor is damaged, it is possible to repair only a section without tearing up the whole floor. However, because the subfloor is so concealed, it’s not always clear when it has been subject to damage or rot.
Here are a few telltale signs that it might be time to build a new or repair your existing subfloor:
- Cracking tiles
- Appliances such as an unstable toilet or washing machine coming loose
- Ridges or bubbles in linoleum floor surfaces
- Wooden floorboards buckling
- Inexplicable musty odor
Can I Lay Tiles Directly On The Subfloor?
While plywood can be acceptable material to support a tile floor, make sure you don’t lay the tiles directly on the subfloor structure. Use a second, thinner layer of plywood between the tiles and the subfloor. This will reduce the risk of the floor surface being uneven, which will result in the rapid deterioration of the fragile ceramic tiles.
How Much Does It Cost To Repair A Subfloor?
Plywood and OSB are both relatively cheap materials compared to the price of other lumber. Although repairing or replacing a subfloor can be a time-consuming process, it is pretty affordable when it comes to repairs.
According to Forbes, a small area of a room’s subfloor can be repaired for as little as $100-$200 and replaced for $400-$500. For the subfloor of an entire room, the cost of repair is in the $300-$400 range, while replacing a whole room is quoted at $570-$720.
Plywood is a composite layer wood material that has long been used for practical construction due to its being cheaper than premium lumber. The introduction of OSB shifted public opinion about the value of plywood. OSB is a cheaper and more environmentally friendly option, though many builders still prefer CDX plywood.
While both plywood and OSB boast advantages, flooring and construction experts agree that plywood is the best material for subfloor structures.
Plywood comes in a variety of quality grades, but the lower-end CDX grade panels are perfectly fine for subflooring.