RTD vs CDX - What's The Difference?

A deep dive into commonly available Roofing Ply!

Hey there! It's Brent, VP of Retail & Sales at CBS Bahamas and the CBS PROstore. 

I wanted to write a short blog today to help you understand the differences in Roofing Ply... At our CBS stores; we've become known for consistently selling our top-quality Boise Cascade Roofing Ply for the lowest price in the nation. Offering such a good price on a commodity item such as roofing ply is something that we're very proud of, and we're even prouder to know that we are selling only the best quality materials at these everyday low prices! 

If you didn't know; the roofing ply that we sell is Boise Cascade 19/32" (5/8") 4-Ply SYP RTD plywood - and it's great stuff!

But, I realized (after getting some feedback from customers) that we needed to clear the air on just what this plywood is - and why it's far superior to the more commonly available CDX plywood. 

You see, our customers have informed us that many of our competitors are justifying their higher price point by informing them that their CDX plywood is superior to our RTD plywood... This is a flatout lie & misinformation. Whether our competitors are simply miseducated on the subject or playing devious word games to increase sales; I can't say... But I wanted to take a second to post this blog and inform our customers on just what the real differences are - and why RTD is always the better option.

Roofing Ply in The Bahamas

Roofing plywood is readily available at Lumber Yards and Hardware Stores across the country - the most common size is 5/8" (sometimes listed as 19/32"). This type of plywood is commonly used in general construction for roof sheathing, wall sheathing, and subflooring where it may be exposed to moisture temporarily during the construction process (but not intended for long-term exposure). Generally speaking, this roofing ply is available in both CDX and RTD; bust most commonly in CDX. 

For the most part; retailers offer this plywood at a price around the $35-$40 range per sheet. Here at CBS, we have our price locked in at $33, and often lower it below $30 for various sale events & promos (note; this blog is written in June 2024 and it's worth noting that lumber prices in general can be volatile). It's also worth noting that we offer complimentary mailboat drop off and $5 island-wide delivery - regardless of how many sheets have been ordered. A delivery policy that can't be matched!

Now, here is where the difference comes in & what you, the customer, should be aware of when shopping around. Keep in mind that the vast majority of retailers are selling what's known as 'CDX' Plywood... So let's dive into that!

CDX Plywood

So, what is CDX?

Well, simply put, CDX is an economical construction grade plywood... Let's break down what 'CDX' stands for:
C: The grade of the plywood’s front veneer. Grade C indicates that the front face of the plywood has visible knots and imperfections but is relatively smooth.
D: The grade of the plywood’s back veneer. Grade D indicates a lower quality veneer with more significant imperfections and knots, which can be larger and more numerous than those found in Grade C.
X: Represents the type of glue used in the plywood. The “X” stands for “exposure,” indicating that the plywood is made with an adhesive that can withstand some exposure to moisture.

It's a solid construction grade plywood, that like RTD, is suitable for a variety of sheathing applications - including roofs, walls, and subfloors.. But, it is economical & somewhat 'old school'. It's a reliable option, but definitely not the best option. Think of it as a basic, entry-level, no frills solution.

So what's the big deal, why is RTD better?

RTD Plywood

In the simplest of terms, RTD plywood is next generation CDX... RTD plywood stands for Resistance Temperature Detector plywood. This type of plywood is noted for its use of a specific manufacturing process that ensures the adhesive used in the plywood is cured at the correct temperature, providing more consistent quality and reliability. Sensors (RTDs) are used to monitor and control the temperature during the bonding of the plywood layers, ensuring the adhesive cures properly. This precise temperature control results in a more consistent and reliable bond between the layers of veneer. The consistent curing of the adhesive reduces the risk of weak spots and delamination, leading to a stronger and more reliable product. Because of the precise manufacturing process, RTD plywood tends to have better overall durability and performance compared to some other types of plywood (such as CDX).

RTD plywood itself does not specify a particular grade but rather refers to the manufacturing process used to produce the plywood. The grades of RTD plywood can vary and typically follow the same grading system as other types of plywood. RTD plywood can come in various grades, depending on the intended use and the quality of the veneers. For example:

RTD A-C Plywood: This plywood would have an A-grade face and a C-grade back, combining a smooth, high-quality face with a less expensive back.

RTD C-D Plywood: This is similar look to CDX plywood, with a C-grade face and a D-grade back, suitable for construction purposes where the appearance of one side is not important.

Conclusion

In conclusion, the important thing to know is that RTD plywood is particularly valued in applications where the strength and reliability of the plywood are critical, offering improved durability and performance over standard plywood types like CDX. If you're into stats - then here is some information you'll find interesting: the moisture absorption rate for RTD is 10-12% vs 15-20% for CDX, the delamination rate for RTD is less than 1% vs 2-5% for CDX - wow! So, I'd say if you are in the market for roofing ply; it'd definitely be worth asking your supplier exactly what type of plywood they are selling.

Why purchase CDX when you can experience the benefits of RTD for the same (or even a lower) price? It's a no brainer!

Here at CBS Bahamas and the CBS PROstore; we only sell RTD plywood, far superior to CDX, and we source our product only from leading manufacturers such as Boise Cascade. To take it a step further our Roofing Ply is of the 'SYP' variety (Southern Yellow Pine) - SYP is known for its high strength-to-weight ratio, making it ideal for structural applications. It is one of the hardest and strongest softwoods available. Our plywood is also has 'Exposure 1' classification which means it offers better resistance to moisture during construction, while also being certified by the Engineered Wood Association (APA).

In short; my reccomendation to you would be to inquire on the specific type of plywood you are purchasing. If the options are CDX or RTD at or near the same price; choose the RTD!

So, to our customers; I truly hope you enjoyed this blog! As always, feel free to reach out if you have any questions at all... We're always available via email at cbs@cbsbahamas.com or just look for the 'Questions & Answers' section of our product catalog pages - post a question, and we will get it answered ASAP!

And, to our competitors; I hope this blog was informative - please stop misleading your customers in the construction of their homes!

Let's #BuildBeautiful,

Brent Burrows II
VP, Retail & Sales