How to Waterproof Plywood – Best Methods for Waterproofing Plywood

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How to Waterproof Plywood


You have been set to the task of renovating your family home, and that includes waterproofing some wood. Or, perhaps you have decided to build a structure that needs to be weatherproof, and plywood is your wood of choice. Whatever your reasons for needing to waterproof plywood, the question remains, will it last throughout the elements of the weather? Do you have the know-how for the task at hand? One needs to make sure their plywood has been waterproofed because water-resistant plywood is simply not sufficient, at least not for most situations. This tutorial is all about how to waterproof plywood and everything you need to know about how to go about how to seal plywood for outdoor use. We will cover all the best plywood sealer products on the market, as well as for instructions on how to weatherproof plywood structures that you are building.




How Waterproof is Plywood?

You have two choices of plywood when buying it from the supply store. There is normal plywood that is not water-resistant, and there is water-resistant plywood. No matter the resistant qualities of the plywood, water from rainfalls will eventually seep through and ruin the wooden structure due to rot. You might begin to ponder how to waterproof plywood, or what kind of plywood sealer might be a good waterproofing agent for the task at hand.

Plywood Sealer Advantages

First, we will discuss what plywood is, and how it came to be. Most hardwood is cut directly from the trunks of trees. Plywood is not exactly natural, being an engineered wood because it is man-made via compacting and gluing very thin slices of veneer together until a board has been made. The glue that is used to compact the pieces of veneer together is what makes it water-resistant, but there are plywood sealers that you can add to the outer layer of the plywood to make it waterproof.

Plywood is a versatile building material that has revolutionized and pretty much taken over the industry since the 1980s. It is much cheaper than natural hardwood, and it can work with many different materials, types of glue, and paints. It can be used when building a house with a budget and even upholstery.


The Advantages of Waterproofing Plywood

Plywood is already water-resistant when you purchase it from the hardware store, but there are still elements that you can add that will make it waterproof, not to mention the aesthetic appeal the finishes give when applied. Here are a few more advantages of waterproofing your plywood with a plywood sealer. By the way: We also have a guide about how to paint plywood.

Thin Plywood Sealer


Longer Lasting Plywood

No doubt simply having water-resistant plywood is not going to be the most long-lasting structure. There are so many things that would affect it, from flood to heavy rainfall that will inevitably seep through the plywood and make it all soggy, or even start to rot. By making your plywood waterproof, you will have a much longer-lasting structure.

These waterproofing sealers not only stop water from leaking through but also preserve the plywood from all other elements like a humid climate.


It Protects Against Rot

The absolute worst nightmare for most people in the renovating business is rot. After all, it is usually something that causes so much more of a cost in repairs because all of the wood must be replaced. If you treat your plywood with a sealer, it will make it waterproof, which will prevent it from rotting at the same time.

Water Resistant Ply


It Protects Against Heat

This is new to most people who live in wet and cold climates. Did you know that water damage is not the only thing you have to worry about when it comes to your plywood structures? There are some serious repercussions that your plywood will experience if you leave it out in the scorching sun all day, and the general wear and tear of the plywood will disintegrate faster if you live in a hot and dry climate. The heat will make the wood break down because the glue that holds all of the layers together will start to melt.

If you add plywood sealer to your structure, you will make it impervious to heat damages.


It Protects Against Fungi

Mold is not only an unsightly thing that forms on the ceilings of our homes and the walls of our bathrooms, it is also a health hazard. It tends to thrive on plywood that has not been treated with a sealer because it is not waterproof. Moisture will seep into the wood and eventually fungi-like mold will start to spread all over the plywood boards. One thing we feel the need to mention is that if you notice any of this mold growing on your plywood boards then you must make sure you get rid of it, and properly, because this kind of mold is very contagious and it will spread all over, making your home smell like damp or mildew.

Water Resistant Ply Spray



Ways of Waterproofing Plywood

When it comes to how to seal plywood for outdoor use, there might be different reasons or why you wish to build with plywood and many other variables that will influence the method you choose to waterproof it. Things like your budget and the time you have to spare for this task will be big game-changers. Let us take a look at the different kinds of sealers that you can use to waterproof your plywood. There is always the element of protection at hand when you are working with these kinds of solutions, so make sure you have the necessary tools, equipment, and protective gear to protect yourself whilst you work. You can even lay down some plastic sheets to protect the ground you are working on.

How to Seal Plywood for Outdoor Use


Liquid Latex

Liquid latex has an amazingly catchy name and a descriptive one at that. From it, you can work out that this type of sealer is a latex-based formula that comes in a liquid consistency that must be applied via two different methods. Either using a spray canister, or you can manually brush it on.

If you choose the spray option, you can buy small canisters that are loaded and ready, like spray paint. Or you can buy it in a large quantity and use a high-pressure spray gun to apply it.

Water-resistant plywood will need a few layers of liquid latex spray sealer to be sufficiently waterproof. We suggest that you pay more attention to sealing the edges of your plywood pieces because that is where most of the water seeps through. Liquid latex is often also an affordable option for waterproofing plywood.


Polyurethane Varnish

Polyurethane is a type of plastic that is used in many industries of the world. It has even been used to make the wheels of skateboards. There is a polyurethane varnish or sealer that you can use to seal off your wooden furniture or even add to waterproof your plywood structures. You can apply it with a sprayer, or by using a brush. Once you have invested in the idea of treating your water-resistant plywood with some polyurethane varnish, you will not be able to add any other treatments to the wood.

Varnish Waterproofing Plywood

So, if you wish to add a wood stain, then you must do so before you apply the varnish. Not only will polyurethane varnish make your plywood structure waterproof, but it also helps to keep it safe from other damages like potential bumps and scratches. The plastic in the varnish creates a durable finish that strengthens your project.


Spray Painting

If you are looking for a good recommendation, we would like to put Rust-Oleum’s professional enamel spray paint forward as one of our favorites. It provides efficient water and weatherproofing, but you must make sure that you have the right kind of spray paint.

Make sure that you read the label before you purchase it – you will be looking out to see if it is oil-based which is perfect as a sealer for plywood because it will bond to the surface.

Because you will be working with oil-based spray paint, you must ensure to get your protective gear, and in particular, you will need your latex gloves to protect the skin on your hands from getting too messy, thus requiring some more hardcore cleaning supplies that might make your hands feel sensitive.


Penetrating Epoxy Sealant

If you are wondering how to weatherproof plywood, this is a good option, It is also an excellent option for all kinds of wood, not just plywood. Even though plywood is not exactly the most natural wood, with beautiful and rustic natural appeal, you may still prefer to leave it unpainted to have the neutral color of the plywood shine through. In this case, you can use a sealer that is a penetrating epoxy sealer. It will help to keep the natural look of the wood you are sealing, no matter what kind of wood you are sealing.

Plywood Sealer Clear

Another fantastic thing about an epoxy sealant is that It dries transparently, allowing the natural colors of the wood to come through without tainting the hues at all. Not only does it make the plywood, or all types of wood in general, waterproof, but it will also make it more impervious to other weather conditions, and any unforeseen damages that threaten to take nicks out of the flush surface.


Wood Staining

One would think that staining wood would be more of an aesthetic improvement than having any actual beneficial properties such as waterproofing. This is not the most expected answer to the question, how to waterproof plywood you are building with. But one thing is for sure, you will be left with a plywood structure that is vibrantly brighter than before the wood staining, and it will be amazingly weatherproof too! You have the choice to apply it manually with a brush-on method, or you can buy the liquid to be added to a spray gun that runs with a high-pressure system.

There will be some fumes present so make sure that you have the right protective gear, including your respiratory mask, and eye mask, so that your eyes and lungs are safe from any stray sprays.



Does Untreated Plywood Last Long?

How to weatherproof plywood will be our next section. We have discussed the different types wood of sealers that you can choose from, of which there are loads of brands all over the world that will have reliable versions. If you have chosen to forgo the resting of your plywood, how long exactly do you have before it starts to weather and disintegrates? Will it crumble within a year? Or more? Or less?

Easy Waterproofing Plywood

Because of the nature of how plywood is made, all of the different layers of veneer that are glued together make it somewhat water-resistant before any treatments are added. This will help to prolong the lifespan of the wood, but it will not last forever. Marine plywood, on the other hand, can last much longer because of the treatments it undergoes in the process of manufacturing the wood.

Luckily, however, most plywood or “normal” plywood is quite long-lasting. It can resist most rainfall unless it is submerged in a flood or body of water for quite some time. Therefore, plywood’s protection will not last forever and you still need to take care of it. You can expect your plywood structure to last a good fifteen to twenty years, in weather conditions that are more favorable to the untreated wood.

If you are living in a hot and dry climate your plywood might start to break down from the heat melting the adhesive that holds the wood together. If you live in a cold and wet climate your plywood might saturate with the rainwater and break apart that way.

If you would like to add another ten years to the structure you are building, we suggest that you choose one of the different types of sealers that you can use to waterproof your plywood boards. Instead of the structure lasting around twenty years, you will have something that lasts up to thirty-five years until it will start to decay!

Various implications will come with avoiding the sealers for your plywood structure. These are problems with mold that are not only ugly but a serious health hazard. It can spread throughout your whole house and make everything smell damp. Or it could start to break down because the glue is melting between the layers of the plywood veneer that is compacted together to make the plywood.

Plywood Sealer

It may not be the most essential thing in the world, because plywood comes already water-resistant. But, if you’re a fan of saving time for yourself, then we suggest taking a day, or a few days to seal all of the plywood you are working with a sealer so that it will last you up to fifteen years longer than if you were to leave it without a sealer at all.



As you can see, plywood waterproofing options are plenty and there are many options to choose from. So, no matter what your reasons for needing to waterproof plywood, whether you are building a boat, a deck, and railing, a chicken coop, or even just a simple weather-proof storage box, we hope this article has provided you with all the know-how and information you may need to get the job done right with the right products, the first time! Here is to happy woodworking and happy waterproofing!


View our Waterproofing Plywood web story here.



Frequently Asked Questions


Is Waterproof Plywood Reliable?

If you were to purchase untreated or marine-grade plywood, you would have something water-resistant and not waterproof. You will need to add a layer of a sealer to make it waterproof and this will only last up to thirty-five years and not a lifetime. There is such a thing as industrial-grade plywood that will be waterproof without the need for sealers.


Is There a Highest-Quality Plywood?

There might be manufacturers that will develop the plywood methods. Some companies might add more of the water-resistant glue in between the lakes of veneer. This might be done at different paces between the various companies, and both of these elements will have an impact on how durable your plywood is. There is always going to be a high-quality and a low-quality variation of plywood, both will be relatively water-resistant and neither will be waterproof.


How Is Plywood Made?

If you are wondering how the name plywood came to be, we would love to enlighten you. When you are referring to the different pieces that are glued together, they are called the “ply”. Once all of the hundreds of layers of ply are adhered to and compacted together, you will eventually be left with something that resembles a board of wood. This is plywood. The last step of the process of making plywood boards is when it is treated with a bit of heat, but not too much to make the glue meet before it can be set properly. Once this is complete, the plywood can be cut to shape and used for whatever you will.