What with it’s incredible strength to weight ratio, it’s no secret as to why plywood is widely used for construction. Used to make walls, roofs, and even sub flooring, this engineered wood has great shear strength.

Well, plywood is constructed by gluing wooden veneers together. And, exterior graded ply veneers are typically made from Douglas Fir, a highly rot-resistant durable lumber.

But, more importantly, the glue of this manufactured wood is very water-resistant…and this is where things get interesting.

So, in this post, we dive into why RTD plywood’s manufacturing process makes it more water-resistant than other plywood. You will also discover what really goes into each BCX composite plywood sheet.

And keep reading to find out, once and for all, the key difference between BCX plywood and RTD plywood.

Well, BCX plywood is actually a composite graded plywood. The letters reflect the different graded plywood sheets used to make this material.

All plywood sheets are given one of four basic quality grades. These grades measure the ‘finished’ quality of the plywood sheet.

The best quality plywood is smooth, sanded, and pretty much as perfect as it gets for plywood. This type of plywood is Graded ‘A’.

The worst quality plywood sheets are riddled with imperfections, and are incredibly rough to the touch. This plywood is Graded ‘D’.

In between, (at ever lowering levels of quality), are B graded plywood and C graded plywood.

Now, a composite graded plywood sheet is made up of two plywood sheets of differing quality. In the case of BCX plywood, the face (front) sheet is B quality graded plywood. And the back sheet is C grade plywood.

The final letter in BCX plywood refers to the exterior graded glue used to bind those plywood veneers together. The X refers to exterior adhesive. This glue is water-resistant, and doesn’t break down if moisture gets to it.

RTD and CDX plywood are essentially the same exposure 1 graded plywood, except for the superior manufacturing quality of the RTD plywood. This higher quality in the manufacturing process is what makes the RTD plywood a superior product to its CDX predecessor.

But What Makes RTD Plywood So Moisture Resistant?

Well, when RTD plywood veneers are glued together, this is done at a precise temperature. Accurate temperature measurement is responsible for this glues increased water-resistant capabilities.

Now, in order to measure this precise temperature, RTD plywood manufacturers use a device called a Resistant Temperature Detector (RTD). And this process makes RTD plywood adhesive capable of shrugging off any possible delamination problems.

In other words, the RTD treatment process makes plywood glue so water-resistant, it can handle very high humidity environments.

Is RTD Plywood Better Than CDX Plywood?

When it comes to your choice of exterior grade plywood, CDX is the most cost-effective.

Using water-resistant glue, CDX plywood glues the two lowest grade plywood sheets together. Which means that this particular plywood sheet is riddled with knots and other flaws right across its surface.

Yet still this plywood, (often made from Douglas Fir wood), will hold up well in high humidity climates.

However, RTD Plywood can often handle wet conditions much better than CDX. To put it simply, CDX can cope in humid environments. While RTD can handle absolutely relentless high humidity conditions.

Regardless, any RTD plywood that has been APA rated for sheathing, is perfect for roofing.

So Can RTD Plywood Get Wet?

The wood used to manufacture exterior graded plywood, (such as BCX and RTD plywood), comes from stable types of wood.

You see generally, if wood gets wet, it can shift around and warp. That’s because wood will soak up water like a sponge, causing wood fibers to expand and swell. And then as that water evaporates afterwards, the wood dry’s out, shrinks, and warps.

However, some wood types are naturally stable, meaning they do not warp if they get wet. For example, Douglas Fir wood is an very stable. It is durable, and rot-resistant.

So, BCX and RTD plywood are made from stable timber, such as Douglas Fir. Plywood made from this timber can get soaked again and again, and never suffer severe warping or wood rot.

So, when it comes to exterior graded plywood, wood rot and warping aren’t an issue. It’s simply delamination that needs to be prevented. And preventing delamination comes down to the quality of that plywood’s adhesive.


What does RTD on plywood mean?

The “RTD” in RTD plywood stands for Resistance Temperature Detector. You have your normal CDX plywood for exterior sheathing. This plywood is made to function better outdoors – deals with temp changes and moisture better than other forms of plywood.

What is RTD plywood good for?

Exterior panels sometimes referred to as RTD sheathing, are designed to hold up to constant moisture. They are completely waterproof and are great for installing in places where you expect consistent exposure to moisture. This RTD sheathing is great for roofs and other outdoor applications.

What is CDX plywood used for?

It Is Very Durable

It is one of the strongest and most durable types of plywood out there. This is not only due to the fact that it resists delamination very well, but also because it’s made out of high-quality wood. RTD plywood can take quite the beating without wearing down.

Related Posts