May 11, 2021

Best Way to Waterproof Plywood

How to waterproof plywood

What is the best way to waterproof plywood? Plywood is considered a durable and reliable wood material that you can use for various purposes, including construction and renovation. Its strength is considerable; therefore, many do-it-yourselfers have begun to opt for this method.

The longevity it offers is not comparable to many other options on the market. One of the most attractive aspects of this product is also its price. It is quite affordable and therefore many people are willing to buy it, although it has a very distinct disadvantage.

Exterior plywood is not very well designed to cater to moisture, and this is a widespread problem that everyone faces when they use this wood because it will begin to swell when exposed to water. 

This swelling helps nobody as it begins to tear off the paint and rip apart the internal structures. Once the moisture has dried, the wood will then start to fade. This is even worse because this wood’s strength benefits go up in flames.

To reap all the advantages of this wood, we must waterproof it. This will work hard to ensure that this wood’s interior and exterior structure does not crack even when exposed to water damage. Waterproofing the plywood will also prevent any unnecessary decay, thereby prolonging the life and performance of this product. 

Fortunately, it is not very difficult, and the materials required can be found in almost any hardware store worldwide. The process itself is pretty straightforward, depending on the quality of wood that you have chosen. Therefore, this guide will work out the best way for you to go about it, even when dealing with rough surfaces.

Reasons for Waterproofing Plywood?

  1. Rot and Decay

Exterior Woods is known as the superhero of the wood world due to its excessive strength and durability. What they cannot deal with is water. Many kinds of wood are highly susceptible to moisture and rot and decay because mold loves to eat wood. This is quite natural and is often affected by the humidity of the wood’s area. Most of the time, it is too late once a piece of wood begins to rot. 

At this time, the mold will only start to spread like cancer and damage the wood internally. It would help waterproof plywood because it will allow you to maintain the appealing look of the item you have created. Such products often have a financial value, and preserving them for as long as possible is essential. It will be unlikely that you will experience any mold on it after sealing the wood for a very long time.

  1. Protection against the sun and rain

Once any water has managed to get into the piece of plywood you’re working on, it will likely cause a large amount of rot. Rain is notorious for damaging wood because of its relentless nature. Once it penetrates a section of the wood, the rain keeps falling, hammering down this position like a nail. Over time you will find that there will be a large amount of damage done to the plywood material. This can render it useless and leave someone feeling quite frustrated.

Aside from rain sunlight, Rays also carry quite a powerful punch when it comes to wood. Twisting will likely occur when it is boiling and the sunlight Rays are beaming down at the wood. After some time of this occurring day in and day out, they would likely lose all of their previous beauty and turn into quite an eyesore. Given that the sunlight Rays will contribute to the swelling and compression of the wood, it is only likely that the wood will fail structurally quite soon.

  1. Balanced Integrity 

Even if you take away the more dangerous elements of the environment, there are still many things that can happen to wood naturally. Preserving any wood is normally done worldwide to keep the structural integrity well balanced. This means that you will now be holding it against something like insects, which can cause significant problems to furniture.

How to Waterproof Plywood?

Things you will need 

  • An appropriately sized brush for the wood you have
  • Sufficient Polyurethane Varnish
  • Some masking tape

Weatherizing a piece of wood will allow you to ensure that it lasts for quite a long time. Gaining years out of a project will take you around one or two days of work is a significant investment.

Step 1: Sanding 

First, we must prepare the wood by sanding it to achieve a very smooth finish. This can be done using sandpaper that has a grit of 80. You may keep repeating this procedure until you have reached the required smoothness, even if you have to increase measurements. 

You must get a clean cloth dipped in a bit of water to remove all the dust on the wood. We do this to avoid sealing Dustin with the wood over time.

Step 2: Apply Polyurethane Varnish

Now we want to get our paintbrush out and add a bit of the polyurethane varnish to the ends of the wood. The edges of the wood are the most complicated and essential to varnish because of the oxygen gaps. 

You will want to get the masking tape out and cover the surface of the wood to prevent the oil from hanging around on the surface. What we want to achieve here is for the wood to absorb this varnish and sealant. 

Therefore once you have covered the top part of the plywood, begin to paint on the sides. As you complete this first coating, you must allow the wood some chance to breathe and allow the varnish to dry for 30 minutes. Once this is complete, we repeat the process until we put in several varnish coats.


In conclusion, this is quite a necessary process to be undertaken to improve the product’s durability. To fully harness this strength capacity, you must seal it against any potential intruders. Mold, water, and sunlight can be big problems for any outdoor plywood furniture.

Therefore, you must apply several coats of varnish to the product to help it defend itself. The procedure will not take you very long, possibly a maximum of two days. This process is referred to as weatherizing a piece of wood, and it is quite an investment because it will allow you greater longevity.

See our post on: Marine Plywood Alternatives.

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