You might be familiar with some materials required to build a house, but there are specific ones you might need to learn about; a good example is roofing plywood. Why? When you don’t know what wood is suitable for roofing, it can lead to a leaky roof or worse damage to your home furniture.
This is where the terms CDX and OSB come in. You do not have to worry if you don’t know what they mean. In just a moment, you’ll learn what CDX and OSB are and which type works best for your roofing plans.
CDX and OSB are two types of plywood that can be used in roofing your house. While CDX plywood is considered a common material for roofing and walling a house, OSB is an engineered wood that has gradually overtaken CDX in popularity. Depending on your preference, you can use any of these options to roof your house, but you should consider durability, price, dimensional stability, and sheeting before making your choice.
CDX
While you might be familiar with the acronym CDX, it refers to the grade of plywood it falls under. Plywood is a type of engineered wood that involves folding thin veneer sheets that are glued together with glue.
Plywood is often categorized into grades A to D. So, the CD in CDX refers to plywood with thin veneers of grades C and D glued together. This is not to say that the CDX is low-quality plywood; rather, the wood has more visible flaws and knots. You definitely won’t be using a CDX for any obvious woodwork.
You might wonder what the X stands for in CDX; contrary to a lot of what people say, the X does not stand for excellent, rather it refers to both the glue used to hold both grades of plywood together and exposure which shows that the plywood can endure a level of vulnerability to water and insect attacks.
What is CDX used for?
CDX is appropriate for both interior and exterior home construction tasks. Contractors commonly use CDX Plywood for external surfaces such as walls and roofing. In this situation, it is not used as a primary material. However, they are used in various applications like roof shingles, roofing felt, sliding, insulation, etc.
Inside the house, CDX plywood is utilized as a flooring layer beneath a carpet cushion or backer board for tiling. It is also used for basic utility tasks such as shelves, cellars, storage, cabinets, etc. It is typically not used for furniture elements because such products require considerably more finesse-based details.
OSB
OSB stands for Oriented Strand Board. Unlike CDX, which is made by combining thin veneer strips, OSB is made using a different approach. It is also a type of engineered wood.
In making OSB’s wood, materials such as chips, resins, and waterproof heat-cured adhesives are combined and thoroughly heated into different block shapes. Most of the time, crooked, knotty, and deformed trees that would otherwise go unused are chopped up and combined into OSBs.
Each layer’s wood strips are intentionally positioned rather than randomly for strength, and the product can include up to 50 layers of wood. The wood is extremely sturdy because it is obtained from small, quickly growing, sustainable trees like southern yellow pine and aspen poplar.
To ensure that the quality of each panel of OSB remains constant, the material is fabricated in large, continuous mats that are then cut into individual boards.
Types of OSB
OSB is classified into two types: OSB2 and OSB3.
OSB2 is excellent for non-load-bearing structural projects in dry conditions, while OSB3 excels in load-bearing structural applications and humid environments.
What can OSB be used for?
One major highlight when looking at CDX vs. OSB is what they both can be used for, and this important detail could sway your decision one way or another. Like CDX, OSB is a very versatile type of engineered wood, as it can be used for flooring, subflooring, roofing, decking, wall sheeting, cabinets, and furniture making.
OSB is quite popular in the market because while it may not be the most beautiful wood to use, it has a finer finish than CDX. It is also more affordable than CDX. Its affordability is a result of the procedures used to make both types.
Should You Use CDX or OSB For Roofing Plywood? (Price & Durability)
A must-ask question in deciding on the type of roofing wood is, what should I use for roofing my home, CDX or OSB?
There are many factors to consider before picking your preferred wood, ranging from the wood’s durability to its cost. The choice lies with you, but the pointers below can help you make a more informed decision that caters to your needs:
Durability
This refers to how well the material can withstand pressure or damage. In the case of both plywoods, we would pay more attention to how they deal with moisture.
There is a difference between CD plywood and CDX plywood, and it is the presence of the X factor. The X, as mentioned earlier, refers to exposure and the glue used to bind the thin veneer sheets together. It also gives the plywood a level of water resistance.
Its water resistance works because it can withstand exposure to water for a limited time. However, it isn’t fully waterproof and can get damaged from prolonged exposure to water. This continuous exposure to water may result in leakages without deforming the wood too badly.
OSB is also very durable. Its manufacturing process involves compressing a lot of wood, resin, and adhesive under pressure. This makes it strong, durable, and fairly water-resistant. The major catch here is that when there is prolonged exposure to water, it begins to lose its shape.
Sheathing
Sheathing refers to the outside protection for the house, including but not limited to boards and panels that line the house’s walls. It’s possible to use a wide variety of materials for sheathing a house. Still, they all serve the same purpose: creating a foundation upon which additional components, such as walls and roofs, can be installed, strengthening the structure, and improving the home’s insulation.
Water resistance is also a major factor for sheathing. OSB is an excellent substitute for CDX due to its superior moisture resistance. OSB lasts longer in harsher conditions because of the glue and resin used in the wood chips to make it far less porous. OSB is sometimes used to reinforce homes against hurricane occurrences.
CDX expands uniformly when wet, which is noticeable throughout the sheet. Drying out and shrinking back to normal happens rapidly, and the minor swelling it experiences seldom affects roof finishes. This favors CDX because OSB does not return to its shape as it swells out of proportion when it soaks in too much water.
Cost
Regarding cost, other types of wood offer less value for money than CDX or OSB. That being said, OSB is much more affordable than CDX.
OSB ranges in price from $32 to $77 per 4′ by 8′ sheet, with the average being $45. Meanwhile, CDX goes a bit higher than that.
If you are working on a tight budget, getting OSB plywood can be a possible option. On the other hand, CDX remains a very favorable option when looking for roofing plywood.
One more advantage OSB has alongside its price is its availability across stores and lumber yards.
Dimensional stability
This refers to how each piece can take in water and retain its shape after drying out. This can be considered a test of how each plywood can return to its original form after absorbing moisture.
OSB is widely believed to be watertight; however, it does have several drawbacks. Even though OSB is water resistant, it takes a long time to dry out once it has absorbed any. This makes it difficult for OSB to restore to its natural state.
CDX is not waterproof and readily accumulates water, yet it rapidly releases this water and returns to its former shape. Consequently, it has better dimensional stability than OSB.
When choosing roofing plywood, your climate or location plays a huge role, especially if you are unwilling to bear permanent changes in case of heavy moisture absorption.
Which is the best?
Determining the best plywood might be challenging considering the various beneficial criteria CDX and OSB. While a sizable number of people believe that CDX is a better option for roofing, some experts believe that OSB is truly better, all factors considered.
While CDX and OSB have many parallel applications, their unique capabilities mean that each is best suited to a specific type of task.
Subfloors are best installed with CDX. Not being subjected to heavy precipitation or humidity helps keep it in good condition. It’s also a common material for roofing sheathing. CDX is strong and useful if you treat it well. Keep it covered both times, and give it the attention it needs to avoid injury.
If you need a substrate for roofing or decking, OSB is your best bet. This is because it can withstand wet conditions without being harmed, at least for a considerable time.
The OSB roof sheathing appears to be effective as well. However, you should also make sure the edges are coated with a water-resistant material. This is done to stop the wood from taking in water, which causes permanent distortion of its form.
Here is a table comparing CDX and OSB to help clarify your choice:
| CDX | OSB | |
| Durability | CDX is not as durable as OSB | OSB is considered more durable |
| Sheathing | It absorbs water faster and also releases faster | It is more water resistant. |
| Cost | More expensive than OSB | Less expensive than CDX |
| Dimensional Stability | Has more dimensional stability | Has less dimensional stability |
Conclusion
At the end of the day, choosing the best roofing plywood to use for your house is yours to make. It is crucial to consider the criteria highlighted in this guide before doing so.
Examine the durability of the plywood, check if the cost matches your budget, and consider all other factors before making your decision. You can surely never go wrong by reviewing these details. Also, you can get a professional consult with your findings and any other concerns to make a more informed decision.
Ruben has a diverse background in the home services industry, with experience running a construction company, a kitchen and bath showroom, and a moving and relocation company. This breadth of experience has provided him with a wealth of knowledge and expertise in various areas of home improvement in general and specifically in the heating and plumbing niche.