What Is The Best Plywood For Outdoor Use? (Solved!)

So, the time has come for you to build your own backyard fortress of solitude. Or maybe you’ve decided it’s time to build your own gym – and you’ve earmarked a corner of the yard for that gym shack.

Either way, plywood is one of the most cost-effective materials for constructing buildings – both big and small.

There are many different grades of plywood. But not all are made equal when it comes to weathering the elements.

So, what is the best plywood for outdoor use?

  1. Exterior Rated Plywood: The veneers of these particular plywood sheets are glued together with a water-resistant adhesive. That is why this manufactured wood is great for outdoor constructions.
  2. Marine Grade Plywood: This plywood type can be permanently submerged in water. However, marine grade ply is up to 10 times more expensive than exterior rated plywood.

Still, with all of the different grades available, what type of exterior graded plywood should you buy? And why is marine grade plywood so expensive?

Well keep reading to discover how you can choose the right type of plywood for your outdoor project.

best plywood for outdoor use

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Is Plywood OK For Using Outside?

Yes, but only if it is a plywood type that has been specifically created to be water-resistant.

This is achieved when plywood is glued together using a waterproof adhesive. This makes the plywood stronger – even when it’s repeatedly drenched by rain.

Can Regular Plywood Get Rained On? No. Regular graded plywood will warp if it is exposed to water for a prolonged period of time.

What Type Of Plywood Is Waterproof? (Exterior Graded Plywood v Marine Grade Plywood)

Marine Grade Plywood:

This incredibly strong ply is made from premium quality Douglas-fir or Western Larch wood. Constructed from high-grade veneer, this plywood is used to construct decks and boats.

Marine Grade Plywood is arguably the strongest plywood on the market, and its eye-watering price reflects that. A 4×8 foot sheet of exterior graded plywood can cost around $10 a sheet. Marine Grade Plywood, on the other hand, costs roughly $100 per 4×8 sheet.

Exterior Grade Plywood:

Exterior Grade Plywood, (also known as construction-grade plywood), is made from regular grade plywood sheets. Yet, these sheets have been fastened together using water-resistant ‘Exterior Glue’. Exterior grading is usually indicated by adding an ‘X’ letter to the standard grade of a sheet of plywood.

This plywood version doesn’t have the same level of waterproofing quality that Marine Grade Plywood has. Still, it can easily handle long-term exposure to the outdoors.

A popular exterior grade plywood is ACX plywood. That’s because ACX ply sheets combine quality with affordability.

And then there’s BCX plywood.

In a nutshell, this kind of plywood is made by sticking B-grade and C-grade sheets together with waterproof glue. It has a smooth finish on one side, and the other is rougher to the touch – like it’s been scratched up a bit.

If you’re curious to learn more about why BCX plywood tends to be so popular for outdoor construction, check out this article: What Is BCX Plywood? (Everything You Need To Know)

CDX graded ply is a much cheaper exterior grade plywood type. However CDX’s low-grade veneers are rife with flaws and knots.

Is ACX Plywood Exterior Grade? Yes it is. The ‘X’ in ACX indicates that this type of plywood has been glued together using a water-resistant glue.

What Is Plywood Grading All About?

There are four standard plywood grades, rating from A down to D.

Plywood that is rated ‘A’ grade is the best of the best. It has been sanded down smooth, and is ready to go for staining, a coat of glossy paint, or finishing.

Plywood that is graded ‘D’ is of the lowest quality. These low graded panels are usually pretty scruffy and riddled with splinters.

You can also get what are called ‘composite graded’ plywood, like AB, BC, CD grades and so on. These plywood grades refer to the fact that two differently graded sheets of plywood have been glued together.

The first letter in the grade refers to the ‘Face’ sheet, while the second letter refers to the ‘Back’ sheet.

So, What Type Of Plywood Is Best For Outdoor Use?

ACX exterior graded plywood is the best option for outdoor building. It is relatively affordable, and doesn’t sacrifice quality for price.

However, if you are working with a tight budget, then consider buying CDX plywood. Still, it is worth noting that this particular type of construction-graded plywood, both looks and feels rather shabby. So, it is more commonly used as sub-flooring material.

However, if plywood is going to be exposed to extremely wet outdoor conditions, then only marine grade plywood will do.

This type of plywood is often used for boat flooring. But, what sets Marine plywood apart from regular plywood is that it is more waterproof than other types of exterior plywood due to its weather and heat proof glue and void-free sheets.

Learn more about this special (and rather expensive) type of plywood over here: What’s The Best Kind Of Plywood For A Boat Floor?

What Is The Difference Between Exterior Grade Plywood and Pressure Treated Plywood?

Pressure treated plywood has been put through a chemical process that injects preservatives into the wood. Those preservatives help make plywood less susceptible to bugs, mold, and rot.

Exterior graded plywood refers to ply sheets that have had their veneers glued together with waterproof glue.

Now, not all exterior graded plywood comes with chemical treatment as standard. But you can, (and always should), buy exterior graded plywood that has been pressure treated.

How Long Will Exterior Graded Plywood Last Outside?

Pressure treated exterior graded plywood can last roughly 20 years – even in rainy and/or humid climates.

But this is only if the plywood has been properly sealed (especially along those tricky exposed sides).

So, how do you seal exterior plywood? Well, I wrote a useful guide to sealing plywood that you can check out right now. Click here to find the complete ‘Beginners Guide To Plywood Sealer (What You Need To Know)’.

Final Thoughts

At the end of the day, when choosing the best plywood type for your building project, ACX rated plywood tops the rest.

ACX exterior rated plywood is an affordable weather proof building material. If you want to save a bit of money, you can use low-grade CDX rated sheets. However, you will need to be prepared to sand and smooth out that rough plywood before you use it. Marine grade plywood is also very weatherproof, but it is a lot more expensive than ACX plywood.