The affordability, versatility, durability, and aesthetics of plywood make it a popular choice for indoor and outdoor projects. You must have made up your mind about plywood & now you are considering whether to waterproof the plywood or not.

There are different versions of plywood & some claim to be water-resistant, so is it redundant and a waste of money to waterproof the material?

Let’s deep dive into this matter and see why waterproofing is recommended & how to waterproof plywood.

Is PlyWood Water Resistant?

Plywood is engineered wood with several layers of paper-thin materials called veneers bound to each other using adhesives.

These materials have water-repellent properties in them, but not enough to safeguard plywood from prolonged exposure to moisture. The layered structure also makes it vulnerable to moisture.

So, in simple terms, plywood is vulnerable to water damage. If you were planning to use this material for outdoor decks, boat decks, or on the boat itself, don’t let this one drawback compel you to throw in towel on the idea.

Because the good news is that the porous structure makes it easy to bond with waterproofing material. Waterproofing can prolong its life and make it less susceptible to cracking, rotting and deterioration.

What are the Benefits of Waterproofing Plywood?

It is natural for us to need enough reasons to proceed with spending more money and taking the time out of our already busy lives to do something like waterproofing the plywood material.

If you are still on the fence about waterproofing, let us give you sufficient ammunition to get your hands dirty, with waterproof sealers obviously!

The whole process of waterproofing the wood is done to prolong its lifespan. Usually, even with extreme care, plywood would last only up to 2 years. With proper waterproofing, you can make it durable for up to 20 years!

Let’s walk through how a simple process of waterproofing can keep plywood structurally sound and last longer.

1. Prevents Rotting:

Constant touch with moisture/water can cause the plywood to rot. It would not only look bad but also, gives off a bad odor. And, you would don’t want that!

Waterproofing the plywood before installation can save you the hassles of dealing with misshaped, foul-smelling wood.

2. Fend Off Dry Rot:

What is the difference between rot and dry rot?

The consequences of rot and dry rot are the same. But, when it comes to the case of dry rot or otherwise known as brown rot is that here the culprit is fungi.

Cellulose or hemicellulose components in the wood (any wood in that case) give the wood products strength and persistence. Fungi disintegrate these materials and cause the wood to deteriorate. Waterproofing can help make the wood resilient to dry rot.

3. Lessen The Splitting:

The expansions and contractions in the wood due to moisture and humidity can lead to wood splitting. You can keep your wood from splitting by waterproofing it

4. Prevents Wood Warping:

Warping can make your plywood looks like it’s deformed.

This happens when the moisture content in the wood changes unevenly. And, sun rays hit different parts dry differently changing the shape of the wood.

The solution is again waterproofing!    

What are Different Methods Of Waterproofing Plywood?

Now, let’s get to the business. We have been walking you through the benefits of waterproofing your plywood.

How would you proceed with it?

What are the methods available out there which would fit your needs and bill the best? 

Before, discussing in depth the ways to waterproof the wood, you would also like to get a basic idea of preparing the plywood for waterproofing.

How To Prepare Plywood For Waterproofing?

  • As a first step, you can set up a place to get on with the business of waterproofing.
  • You can lay down a tarp or newspaper to prevent the floor from getting dirty.
  • Clean the plywood and look for rough spots or grooves as this can make the surface uneven post-waterproofing. 
  • You need to sand the plywood surface with sandpaper (180 to 220 grit). Sand the surface, corners, and throughout to give it a smooth surface.
  • The next step is to apply wood fillers to fill any gaps that might impede waterproofing. Let it dry overnight before proceeding with waterproofing.

 Now that you have clue about how to do it, let’s look at various waterproofing sealers that can be used. We have made a list of five top methods for you.

1. Use Epoxy Sealer To Waterproof Plywood

Waterproof epoxy sealer

Epoxy sealers are the most popular choice of waterproof for plywood. Epoxies are used even for waterproofing boat parts!

So, this must be an excellent product to waterproof your outdoor deck or kitchen deck.

There are multiple reasons behind the same. One of which is that with the epoxy sealer you wouldn’t need to worry about ruining the aesthetics of your wood. Epoxy sealer is clear unless you are thinking of adding dyes to it for color.

The second advantage of epoxy is that it makes the wood highly resistant to dents, dings, and scratches as well.

Epoxy can be applied in the following steps:

1. Mix the epoxy with the hardener: Epoxy sealers come with a hardener, you can mix these as per the instructions to get the final product (It is advised to choose a cooler day or evening to do the waterproofing with epoxy. A sunny day might contribute to air bubbles in the wood).

2. Use a paint roller to apply the mixture. Don’t forget to apply it on the edges and sides. This mixture dries very fast so paint it fast before it dries up.

3. Apply the next coats only after 2 or 3 hours: You can use a hair dryer on the surface if there are any air bubbles.

4. You would also need to tip the surface to correct the strokes from the paint roller.

5. Let it dry for a week: You need to wait until the epoxy has completely hardened before proceeding to install or use the wood.

6. Seal it with a UV-resistant coating: As the last step, you can give a thin coating of any UV-resistant top coat. For this, you can use a paintbrush or a roller. Stick to the instructions and let the wood dry as mentioned in it.

2. Waterproof Plywood With Varnish/Polyurethane

Applying varnish on wood

Varnish is another waterproofing material you can look into. Varnish, in more accurate terms, polyurethane is a thin and less noticeable resin that gives the wood a glossy appealing look after application.

Varnish is a good choice for decks that will be staying above water levels and not submerged. It is also an extremely versatile sealer that will make your plywood resistant to moisture, mildew, and scratches.

There are mainly two types of polyurethane resins;

  • Water-based
  • Oil-based

Oil-based polyurethanes provide more durability to the wood than water-based polyurethanes.

Also, bear in mind that, you won’t be able to apply any other food finishes once you have used varnish on the plywood. Before, you waterproof the plywood with varnish, make sure that you have done any changes that you wanted on it. 

Now, let’s see how can we apply a varnish over plywood the proper way:

1. Use a Sanding Sealer:

Before applying varnish, apply a thin layer of sanding sealer to the wood. It will take almost an hour to dry. After that, you can use 220-grit sandpaper and make the surface smooth.

2. Apply the Varnish:

Use a paintbrush or paint sprayer to administer the varnish to the plywood. Make sure that you cover the whole wood including the edges and ends.

Oil-based polyurethane may take only hours to dry whereas, a water-based will take 24 hours. Once the first coat has dried completely, you can go ahead and apply a second coat. 

3. Let it Dry:

‘Patience is a virtue’! Especially, when it comes to the drying part of the plywood after the varnish application. It might take around 30 days for it to dry and be used for installation.

3. Use Drying Oil Method To Strengthen Plywood

Drying oil is the go-to method if you want to maintain the natural flexibility & moisture of the wood.

With other methods such as epoxy or paint the products create a shell around the plywood to protect/ block it from the water or moisture content.

But here, the substance soaks into the pores of the wood. It doesn’t exactly make the wood ‘waterproof’ but strengthens the wood from water damage. Because of the same reason, it is recommended to reapply the drying oil frequently to maintain the effect. 

The application of the drying oil can be done in simple steps:

1. Prepare the Wood:

As mentioned in the previous session before the application.

2. Rub the oil over the Plywood:

You can use a single oil or can use a combination of oils ( tung oil, boiled linseed oil, or mineral oil) to waterproof the plywood. Wipe off the excess oil using a rug or a cotton cloth. Let it dry before applying the second coat.

3. Sand the Wood:

This time, sand the wood with 80-grit sandpaper and create a small layer of sawdust. Apply the second round of oil along with the sawdust. This would help in filling the pores in the wood as the oil will absorb the sawdust too while it dries.

4. No need for Waiting:

You can use the material for application once you have coated the oil over it.

4. Use Liquid Latex/Spray-On Latex For Waterproofing of Plywood

Liquid latex or spray-on latex is probably the easiest and most cost-effective method of waterproofing techniques. This substance seals the porous layers of the plywood and makes it impervious to deterioration that might happen from contact with water.

You can buy a spray-on or paint sprayer to apply the product. The other biggest advantage is that you get to choose a color of your own choice.

It comes with a set of disadvantages also. You may need to repaint it from time to time. To repaint, you will have to strip the old paint away and start with the new paint again.

Also, though this method is highly effective and can be used in high-moisture areas, it is better to seal the edges of the plywood with another sealant.

When using the spray method, there are two things you need to take into consideration. Since spray-on sealers are more difficult to manage than brushed-on sealers, you may not get proper control over the process. Make sure that:

  1. You are covering the whole wood by taking a sufficient amount of paint.
  2. You are distributing it evenly and not causing the plywood to have a spotty concentration of paint.

5. PVA (Polyvinyl Alcohol)

PVA or Polyvinyl Alcohol is a colorless, non-toxic adhesive. It has been used as a waterproofing material by many. There are many advantages of using a PVA for waterproofing. This includes:

  1. Since it is a non-toxic material, you can use it on the plywood that will be installed in food preparation or living room areas.
  2. You can sustain the aesthetics of your plywood as PVA is colorless and wouldn’t ruin the beauty of your wood.
  3. PVA retains the flexibility of the plywood.

Have you been considering taking the aid of PVA to safeguard your plywood? But, how do we apply PVA to plywood?

Here’s how:

1. Dilute PVA: PVA is quite rubbery and difficult to apply. You can dilute the glue with water to make it diluted. The rule is to use 1 part glue for 5 parts of water.

2. Apply it to the Plywood: Make use of a synthetic bristled brush.

Once the first layer has dried, you can go up to three to five coatings.

6. Wood Staining

Even though, not mainly preferred, you can keep wood staining as a potential option in the back of your mind.  Wood staining can give plywood protection against water and humidity.

As an added benefit, it also provides a brightened look to your plywood. You can buy the product in a container, pour it into a paint sprayer, and can be applied on the plywood effortlessly.

Frequently Asked Questions

The codes ‘INT’ & ‘EXT’ are used to indicate waterproof ply.

The highest grade of water-resistant plywood is marine plywood.

It would only last around two years. If the plywood is in constant contact with the water, it may only last a few months.


It’s true that no wood is completely impenetrable to moisture and water. But, exposure to these will eventually lead to the decay of the wood.

You wouldn’t be planning to redo your whole project because later in the future, the water caused the degradation of plywood.

The simple act of waterproofing the plywood can save you a ton of money, time, and effort in the long run. Most of all, the process is not that difficult.

Take your time to choose the best waterproofing sealant and say no to water damage.

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