OSB vs. CDX: Which Should You Use?

OSB vs. CDX: Which Should You Use?

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If you are planning on renovating your own home or building a wooden structure, two of the materials that you may use include OSB and CDX. Now, both of them are technically engineered wood products, ones that do share some similarities but are also fairly different from each other.

What we are here to do today is to figure out what both of them are, as well as what their ideal uses are. Let’s get right to it and figure out what kind of engineered wood you want to work with.

OSB and CDX: The Basics

Before we get into talking about the similarities and differences between OSB and CDX, let’s first figure out what both of them are.

What Is OSB?

OSB stands for oriented strand board, and yes, this is a type of engineered wood. OSB is a type of engineered wood that is made by using a variety of adhesives and a lot of pressure to press together wooden flakes into solid sheets of wood.

Although you would not be able to tell based on its appearance, these small strands of wood are oriented in a very specific manner. The wooden strips are very thin and rectangular and are then cross-oriented and bonded together using a mixture of synthetic resin adhesives and wax.

OSB may have a very rough surface and it is produced in various thicknesses and types. It has many applications in construction, particularly load-bearing applications. This is a type of engineered wood that can be used for exterior and interior wall sheathing, subflooring, roofing, and more.

What Is CDX?

In case you have never heard of CDX before, this is quite normal, because it’s usually not called this. Technically speaking, CDX is just a very specific type of plywood. Yes, that is right, here we are talking about plywood.

OK, so first off, plywood is of course another type of engineered wood, one that is made by taking a large amount of very thin veneers or wooden strips that are then glued together. Each one of these strips, or veneers, is just as long as the final product is intended to be.

These wooden veneers are layered together and can have anywhere from five to well over 20 layers. These layers are created using a cross-grain pattern so that each layer is perpendicular to the last, thus allowing for great strength and screw holding capabilities.

Now when we are talking about CDX plywood, that simply stands for the grade of plywood. A, B, C, and D are the various grades of plywood out there, with A being the highest grade and D being the lowest. Therefore, the letter C here represents one side of the plywood and the letter D represents the other.

In other words, CDX is very low-grade plywood, but do keep in mind that this usually refers more to its aesthetic appeal than it does about the mechanical properties and its strength. The letter X stands for exposure and this means that this type of plywood is rated as being somewhat moisture resistant.

Similarities of OSB and CDX

Now that we know exactly what OSB and CDX are, let’s figure out what the similarities between the two are.

#1: General Applications

The first similarity that these two engineered wood products feature is that they are generally used for the same types of purposes. Although they don’t really have the same qualities, both of these products can be used for flooring, walling, and roofing, as well as for other related purposes.

I wrote more about the common uses of OSB here.

#2: Affordability

Now, while one of these types of engineered wood does cost more than the other, when it comes down to it, both of these types of engineered wood are some of the most affordable out there. If you are looking for an extremely affordable building material that won’t cost you an arm and a leg, even for large quantities, then both CDX and OSB are ideal choices to consider.

#3: Both Are Somewhat Water Resistant

OK, so as you will find out when we start talking about the differences between these two engineered wood products, although they can handle some moisture, they are not at all water-resistant or waterproof, especially not in the same ways.

They are quite different from each other in terms of what happens when they are exposed to moisture. With that being said, both CDX and OSB are moisture-resistant in their own ways. In other words, they can handle getting a little bit wet, but what happens when they do differs.

Differences Between OSB and CDX

Now, let’s look at the more interesting part – the differences between the two.

#1: Manufacturing Process and Overall Strength

The biggest and most fundamental difference between these two wood products is how they are made. OSB is made using small wood chips or wood flakes that are then glued together. On the other hand, CDX is a type of plywood that uses very long and thin wooden veneers that are oriented in a cross-grain pattern.

This, therefore, means that CDX plywood is quite a bit stronger than OSB. It can just handle more punishment, more pressure, and more weight. When it comes to being structurally sound, CDX is the stronger option. This is not to say that OSB is not strong, but just not as strong as CDX.

#2: Effects of Moisture

OK, so a big-time difference that you need to be aware of here is that CDX plywood is not all that moisture-proof. Yes, the letter X in the name of the description does imply that it is water-resistant, and while this is true, it is only water-resistant for a fairly short period of time.

Plywood will absorb some water, but it then also dries out quickly and it really doesn’t change its shape very much. However, if plywood like this is exposed to far too much moisture over a long period of time, it will start to degrade. To prevent that, you can waterproof it.

OSB on the other hand is a lot more water-resistant in terms that it does not absorb water easily. However, when OSB does absorb water, it hangs onto it for a very long time and has a tough time drying out. Moreover, OSB does tend to warp and change its shape when it gets wet, and even when it dries, it may not go back to its original shape.

Therefore, as you can see, while both these engineered wood products are water-resistant in their own ways, they both aren’t waterproof.

#3: Appearance

Another difference between these two wood products that you need to be aware of is that while both don’t look very nice, OSB may look a bit better than CDX. Remember that CDX plywood is a very low grade of plywood, and it tends to have a lot of holes and knots. That makes it not the best choice for anything that can be seen.

While OSB doesn’t look amazing, it does look better than CDX, and it is also easier to paint and sand than CDX.

#4: Cost

Although both of these engineered wood products are very affordable, OSB is a bit cheaper than CDX.

OSB vs. CDX: Which of the Two Should You Use?

When it comes down to it, both OSB and CDX are ideal engineered wood products to use for a variety of applications, particularly for walling, roofing, and flooring.

With that being said, CDX is ideal to use for subflooring when it comes to interior use, as well as for wall sheathing. However, OSB tends to be the better option for use as substrate underneath shingles (for roofing), as well as for substrate for decking.


There you have it, folks. Everything you need to know about the differences between CDX and OSB. Now that you know the differences between these two types of engineered wood, you can make an informed decision as to which one to use for your next project.