The Different Exterior Plywood Grades and Their Uses

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Plywood has become a widely used outdoor building material because of its adequate strength and affordability. However, did you know that not all exterior plywood grades can withstand the same external elements and conditions? 

If you don’t want to end up with the wrong variation, here’s a quick guide on how to tell them apart, courtesy of our wood experts. 

What Is Exterior Plywood?

Newbies may not know, but plywood is processed by peeling wood logs into thin veneers. These durable composite materials are joined together by binding, pressing, and heating. 

If you look closer, each layered grain only goes in one direction, and that’s because the veneers are set at different angles. 

Plywood’s alternating layers allow it to reduce contracting and expanding. If you ask our team, this attribute makes it more stable than the typical 2×4 wood. 

Plywood

Its overall composition can resist wrapping, shrinking, or breaking when used as a building material. We recommend using three plywood plies for better durability. The higher the number of plies, the better sturdiness you can expect. 

Different Grading of Exterior Plywood

If you scan the wood market, you’ll quickly realize these plywood materials are graded based on size, thickness, and appearance. Depending on the variation, they are labeled with two to three letters that dictate the plywood grading specifications

The first letter signifies the front veneer grade, while the second letter refers to the veneer’s back. Plywood materials great for exterior use have the third letter, X. With that being said, read along as we examine the great options for plywood to be used for outdoor constructions. 

ACX

As the letter “A” is included in its label, you can expect ACX plywood to be smoothly sanded in its front veneer. It has a good wood grain, making it suitable for painting over.  

Meanwhile, its back is categorized in grade C. This plywood’s tightened knots are around 1 ½ inch with 1-inch knotholes. Although it may have patched areas, you can use it for subflooring projects. 

stack of plywood

Upon our search in the wood market, ACX plywood is widely available in different sizes. Depending on its thickness, you can buy it in variations of ¼-inch to ¾-inch. Some manufacturers even have ones with ⅜-inch thickness through special order. 

ABX

Like ACX, the ABX variations are smooth and paintable materials as they’re graded A plywood types. Because they have visually pleasing attributes, many construction professionals[1] and woodworkers use them for furniture-making projects. Its back veneer belongs to grade B, so expect some patches and filler. 

Most ABX plywood in the market comes in 4 inches x 8 inches in overall size. As for the thickness, your choices are narrowed down to ½-inch and ¾-inch thick. 

CDX

When you go wood shopping, we don’t doubt that you can easily find CDX plywood options because it’s a widely available material. The wood’s face side is graded in the C category. It means that it has knots that are 1.5 inches in diameter. 

It’ll have minimal splits and discoloration, but you don’t need to worry because it doesn’t affect the material’s strength. However, our resident woodworkers still advise using it on non-visual applications. 

choosing plywood

And because its back veneer is also graded D, its flaws are slightly more noticeable than other plywood types. Its knotholes can range up to 2 ½ inches, and its surface is rough and unsanded. 

As for its market availability, you can only purchase it in 4 x 8 inches variations. The thickness options you can choose are ½-inch, ⅝-inch, and ¾-inch. 

Materials Used for Exterior Plywood

As exterior plywood materials are exposed to harsh and changing weather conditions, it’ll help if you could apply a sealant over its surface. Proper sealing can prevent water and moisture from damaging the wood. 

You can opt to use a polyurethane varnish, and we urge you to add two coats for extra protection. On top of that, you can protect its surface of the plywood with waterproof paint. 

Materials like phenol-formaldehyde glue are also encouraged as they can resist exposure to water and weather. 

Conclusion

Now that you’re well-versed in exterior plywood grades, you can lay down the worries of choosing the wrong wood variation. 

Besides inspecting the labels, we suggest taking notes of the appearances and attributes our experts discussed earlier. Through this, you can avoid being duped when you go wood shopping alone. 

Robert Johnson is a woodworker who takes joy in sharing his passion for creating to the rest of the world. His brainchild, Sawinery, allowed him to do so as well as connect with other craftsmen. He has since built an enviable workshop for himself and an equally impressive online accomplishment: an extensive resource site serving old timers and novices alike.
Robert Johnson
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