The quality of your house’s subfloor determines how well the rest of the floor will hold up when in use. For this reason, a lot of focus is placed on the materials and methods used to make the floor. For the materials, the most popular steathing options are plywood and the new oriented strand board (OSB).
While OSB and plywood share many similarities, their differences are the basis of the decisions made when choosing between them. Their manufacturing methods are almost similar but OSB has more structural consistency and is cheaper than plywood. On the other hand, plywood dries up faster when both are exposed to moisture.
In making your decisions between the two, you need to focus on some specifics which determine the environment you’ll expose them to and other aspects.
Subfloor Plywood vs OSB: a Comparison
To understand how the two materials compare, we will focus on the following aspects:
1. OSB has more structural consistency than plywood
To make plywood, thin veneer strips called plies are layered on each other at angles of 90 degrees. After that, the structure is placed in a hot press then left to cool and dry.
OSB is made in almost the same way. However, pieces of veneer measuring between 3 and 4 inches are used instead of long ones. They’re layered at 90-degree angles then glued together and pressed till they make a strong structure.
The two methods, while almost similar, will yield materials with different qualities with OSB having the best possible features. For example, in a similar level of thickness, OSB will have more piece as of veneer (up to 50 pieces) than plywood.
Owing to this, the weaknesses of wood such as knots will be totally eliminated in OSB as compared to plywood. OSB is thus denser and stronger than plywood for your subfloors.
2. Plywood Dries Out Faster but OSB Absorbs Less Moisture
For wooden floors and subfloors, water and moisture are always an issue of great concern as are highly vulnerable to damage by the two. As such, the more material will resist moisture the better.
OSB and plywood offer advantages to the issue of moisture but in varying ways. For one OSB absorbs far less moisture than plywood. This is good since it allows you to notice and take corrective measures against moisture before it builds up too much and causes damage.
On the other hand, plywood dries much faster and more completely compared to OSB. That means that, when both materials are exposed to moisture in similar conditions, plywood will gain more moisture than OSB but will lose it faster as well when dried.
In making a decision purely based on how the two materials respond to moisture, you need to consider:
- How frequently the subfloor will be exposed to moisture,
- How often you check your subfloor for moisture,
- How easy it is to dry the affected areas, and
- Type of material used for the top floor (whether it’s resistant to moisture or not).
This way, you can gauge which one best suits your needs.
3. OSB is Cheaper than Plywood
Already, plywood is cheaper than most other flooring materials on the market that’s why it’s growing in popularity. However, OSB does it one better by not only having the other advantages on this list but being cheaper as well.
Whether you’re going for the low-end or high-end versions of both materials, OSB will always cost less than plywood for the same size of the material. A piece of plywood will cost about $10 while OSB costs about $6. Generally, the installations cost about $ 60-70 per hour (roughly $490 per day) from installation professionals. However, installing sheathing will cost about $150-160 for Plywood material and $100-110 for OSB for about 500 Sqft.
4. OSB is More Resistant to Delamination But Swells at the Edges Due to Moisture Exposure
While both materials are made by laminating pieces of wood together, OSB leads to better results especially when it comes to the density of the end product. For example, when both materials are exposed to moisture, the glue used to hold plywood veneers strips is likely to fail compared to that for OSB panels.
As a result of this, OSB is favored for areas where there is a lot of humidity and moisture as it resists the moisture and doesn’t come loose with moisture in it.
The problem with OSB is that, after it’s dried up and it’s free of moisture, it’ll have swollen edges that won’t just go away. This issue is of such great concern that OSB can fail to work for most floors as it deforms the subfloor greatly.
When you have tiles, for example, they’ll appear saucer-shaped when the subfloor made of OSB swells and loses its shape due to moisture. Plywood, on the other hand, will retain its shape once dry again.
When making a decision, these aspects are what you should put into consideration. If you can overcome the weaknesses of one material over the other, you’re better off going for that material than its alternative.
5. Impact on Resale value for home
Both OSB and plywood subfloor forms part of the home/house structural integrity. However, they are hidden below the floor covering, thus both don’t have any impact on the value of the house unless they are disclosed.
6. Which is a greener option OSB vs Plywood?
Osb is made from small pieces of wood. These pieces can be obtained from a smaller tree with a lower diameter and may grow faster depending on the species used. As such it’s considered a greener option, however, they require the use of formaldehyde which tends to off-gas/toxic.
Plywood on the other hand requires larger diameter trees than OSB. These trees are likely to take a longer time to grow to the required diameter, thus considered a less green option and raises some environmental concerns. But, plywood is currently produced without chemicals as per new laws. Hardwood plywoods use soy-based glues that are free from toxic urea-formaldehyde.
In conclusion it may be possible the environmental concern of fomaldehye may make OSB producer follow suit to a less toxic glue. However, as it is now it may be difficult.
7. Installation methods
Both sheathing or underlayment products tend to be nailed down securely when set in place against the flooring joists. The only difference is OSB tends to be more flexible to work with as a DIY person. However, it also depends on other installation settings such as the distances between joists where OSB and plywood are being installed.
The cost (board+installation) tends to be fairly almost the same for Plywood being about $650 and $590 for Osb per 500sq ft area.
Pros and cons; OSB vs Plywood
Pros of Plywood
Cons of Plywood
Available in many sizes with different finish
Expensive compared to OSB
Non toxic-doesn't contain Formaldehyde from 2019
Less Environmental friendly due to its harvesting and production methods
Less susceptible to water damage
Lower life span , less durable compared to OSB
Can be used beaneath the flooring and for finish work
Available in small panels
OSB-Oriented Strand Board
Pros of Oriented Strand Board
Cons of Oriented Strand Board
Affordable and DIY friendly
Susceptible to water damage, swells.
Heavy, thick and durable material
Can not be painted and has no finished apperance
Larger panels available
Not ment to be used with flooring
Choosing between Plywood and OSB for your Subfloor
When choosing between the two materials, you should look at your current situation and try to gauge what the future will look like with that kind of floor you’ve chosen.
If your focus is on durability, go for OSB it has a more consistent and stronger structure than plywood.
Here is a video of OSB vs Plywood
Source and Reference
- CDC: Indoor Air Pollutants and Toxic Materials.
- CDC: Sources of Formaldehyde.
- ntniehs.nihp: Toxicology Reports of Carcinogen.
- Living-future: Chlorinated Polymers: PVC, PVDC, CHLOROPRENE, AND CPVC.