OSB vs. Thermo Ply: Which to Choose?

OSB vs. Thermo Ply: Which to Choose?

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If you are in the process of building a house, exterior sheathing for your walls is something that you will need to incorporate. Two common materials used for this purpose are OSB and Thermo Ply.

However, these are two fairly different materials with greatly differing properties. Therefore, today we are going to compare OSB and Thermo Ply to see which one is best for your next project. Let’s take a closer look at these two materials.

OSB and Thermo Ply: The Basics

Before we start talking about similarities and differences, let’s first determine what both OSB and Thermo Ply are.

What Is OSB?

OSB stands for oriented strand board. This is a type of engineered wood panel that is made by layering rectangular scraps of wood over one another in a cross-grain pattern. Making sure that the wood scraps are oriented in a cross-grain pattern helps to ensure great durability, hold, and stability. These rectangular scraps or strands of wood can be up to 15cm in length.

When in strand form, they are mixed with a waterproof resin, and then weaved together to form thick sheets. Then, great heat and pressure are used to bond everything together. These building panels are often used for sheathing and other such purposes, are fairly durable, and have a bit of water resistance, although they aren’t waterproof or indestructible by any means.

What Is Thermo Ply?

We then have Thermo Ply, which is another type of engineered wood panel. Thermo Ply is made by taking high-strength cellulosic fibers, or in other words, wood chips, which are then formed into sheets and bonded together using a proprietary water-resistant adhesive.

In this way, Thermo Ply is more similar to particle board than it is to plywood. However, a layer of polymer is then added to both sides to allow for added protection, which also helps to serve as a waterproofing agent and an air barrier at the same time. Thermo Ply is strong, eco-friendly, waterproof, and comes in three different grades, all of which are structural in nature to some degree.

Similarities of OSB and Thermo Ply

Now that we know what OSB and Thermo Ply are, let’s determine what makes them similar.

1. They’re Engineered Wood

Although the build of both is not the same, as one uses wood strips and the other uses wood chips, they are technically both types of engineered wood. Both are made out of broken down wood which is then reformed into solid sheets using adhesives and special processes.

2. A Common Use

Another similarity is that both OSB and Thermo Ply can be used for exterior wall sheathing on houses. Although, this is where the similarities end.

Differences Between OSB and Thermo Ply

Now that we know what makes OSB and Thermo Ply similar, let’s figure out what makes them different from each other.

1. Water Resistance

One of the biggest differences is that although OSB is water resistant to a certain degree, it will absorb water over time, begin to swell, and will eventually crumble. This is especially the case with prolonged exposure. Thermo Ply on the other hand is much more moisture resistant, if not 100% waterproof.

2. Strength and Structural Integrity

OSB is decently durable and does have some structural integrity. However, due to the special bonding process used with Thermo Ply, it is much more durable and stable than OSB. The highest grades of Thermo Ply feature superior structural integrity, which OSB does not.

3. Air Barrier

Thermo Ply makes for an amazing air barrier, which is why it is the preferred choice for exterior wall sheathing. Although OSB does serve as an air barrier to some degree, it just doesn’t stack up to Thermo Ply.

4. Weight and Size

What is nice about Thermo Ply is that you can often order it in custom sizes to suit your needs, which you usually can’t do with OSB. Moreover, a 4’ x 8’ sheet of OSB weighs upwards of 45 pounds, whereas the same size Thermo Ply sheet weighs just 13 pounds.

5. Eco-Friendliness

OSB may contain formaldehyde and other poisonous substances, but Thermo Ply does not, plus Thermo Ply is also made mostly out of recycled materials, making it much more environmentally friendly.

OSB vs. Thermo Ply: Which Should You Use?

When it comes down to it, if you aren’t worried about the cost too much, in terms of strength, flexibility, weight, water resistance, and for use as an air barrier, Thermo Ply is always going to be the superior option.


The simple reality here is that while OSB is fine for sheathing, Thermo Ply is hands-down the superior option in quite literally every way imaginable.