Are you on the lookout for dependable, weather-resistant materials for your outdoor construction needs? With various options available for exterior plywood, it’s crucial to make the right choice to ensure the success and durability of your entire building project.
Rest assured, I’m here to guide you through selecting the ideal plywood for outdoor applications. Read on!
Why Use Plywood Outdoors?
Types of Exterior Plywood for Outdoors
There are many types of plywood for construction. Markings are indicated with an ‘X’ to refer to its intended use for an outdoor project whereas the construction grade is indicated in the first two letters.
Two of the most common are CDX plywood and ACX plywood. I recommend researching the utility grade and the right plywood measurement suitable for your wood project.
CDX plywood is one of the most common types of exterior plywood. It stands out as an affordable and sturdy option due to its construction grade.
Marine plywood is considered one of the highest quality exterior plywood. It is made from premium quality douglas fir. These are knot-free sheets which reduces the risks of water pockets in the wood.
Since there are no visible knots, this makes it more aesthetically appealing. Furthermore, these are best utilized for roof decking and aircraft construction.
This type of exterior plywood is regular plywood that is infused with chemicals fortifying it against mold and mildew.
Oriented Strand Board
Oriented Strand Board (OSB)  is a good substitute and best suited for areas that are semi-exposed to the elements. OSB is stronger in a vertical orientation as compared to horizontal installations.
This type of plywood is most common for siding. It is fairly common and popular due to its natural wood grain overall look.
What Type of Plywood is Best for Outdoor Use?
A budget-friendly option to opt for is CDX. It is built with layers that can withstand extreme weather conditions and is a popular choice for sub-flooring.
Meanwhile, ACX is a pricier option than CDX that’s made from veneers instead of trees. It comes highly recommended for a variety of outdoor and renovation projects.
The most high-end option that is highly durable and weatherproof is marine-grade plywood. Heavy, strong, and waterproof, marine plywood is commonly derived from Douglas-fir or Western Larch trees.
Which Plywood is Waterproof: Exterior Rated vs. Marine Grade Plywood
Both exterior rated plywood and marine-grade plywood are good for outdoors since they are water-resistant and perform well in dry and wet conditions. Here is a quick overview of both plywood types:
Exterior Rated Plywood
I prefer using exterior-rated plywood for outdoor projects. This type of plywood has its veneers bonded with a water-resistant adhesive, making it an excellent choice for withstanding the elements.
Marine Grade Plywood
Marine plywood is smoother and easier to work with. Marine-grade plywood can be submerged in water for long periods of time and thus offers the best water-resistant material and waterproofing among other forms of plywood.
Plywood Rating Explained
The best plywood for outdoor use can be categorized into four standard utility grades. A is categorized as the highest standard plywood and D as the lowest.
The plywood with a utility grade of A is smooth and its surface is ready for staining, painting, or finishing plywood edges and surface. Plywood graded with D on the other hand is non-furnished and splintered.
Composite graded plywood is also possible where different graded plywood is glued together such as AB, CB, CD, etc. The first letter refers to the ‘face’ sheet whereas the second letter signifies the ‘back’ sheet.
(Read more about the plywood grades and standards here.)
Exterior Grade Plywood vs. Pressure-Treated Plywood
Pressure-treated plywood is made by infusing regular plywood with preservatives to make it less susceptible to rot.
Meanwhile, exterior grade plywood is glued together for its waterproofing property, but not all are treated chemically. You can also find exterior grade plywood that is also treated with pressure.
How Long Will Exterior Graded Plywood Last?
This kind of plywood can last up to 20 years as long as it has been properly sealed. And speaking of sealing, you may want to know how to seal painted wood surfaces for exterior use.
Alternatives to Outdoor Plywood
There are several alternatives to outdoor building plywoods. Some alternatives include polyurethane board, medium density fiberboard (MDF), particle board, EKO Ply, high-density fiberboard (HDF), and solid wood.
It’s important to understand that exterior and interior plywood serve different purposes when it comes to withstanding outdoor weather and elements. Personally, I would recommend delving a bit deeper into your research and perhaps seeking advice from seasoned professionals when selecting the most suitable material for your outdoor construction project.
It’s worth mentioning that your budget should also play a significant role in your decision-making process.
Robert Johnson is a passionate furniture maker & carpenter, sought after for his knowledge on the craft.
You’ve probably seen his down-to-earth wisdom in USA Today, Bobvila, Family Handyman, and The Spruce, where he has shared commentary and guidance on various woodworking topics.
Robert is the brain behind Sawinery, where he aims to share tips, tricks, and a passion for all things carpentry.