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.

Its longevity 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 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 tears off the paint and rips apart the internal structures. Once the moisture has dried, the wood will then start to fade. This is even worse because the benefits of this wood’s strength 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 the wood that you have chosen. Therefore, this guide will help you figure out the best way to go about it, even when dealing with rough surfaces.

Reasons for Waterproofing Plywood?

  1. Rot and Decay

Exterior Wood is known as the superhero of the wood world due to its excessive strength and durability. What it cannot deal with is water. Many kinds of wood are highly susceptible to moisture, 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. 

Mold will only start to spread like cancer and damage the wood internally at this time. Waterproofing plywood would help 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 mould after sealing the wood for a very long time.

  1. Protection against the sun and rain

Once water gets 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 much damage will be done to the plywood material. This can render it useless and leave someone feeling quite frustrated.

Aside from the sunlight from the rain, rays also carry quite a powerful punch for 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 become 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 remove the more dangerous elements of the environment, many things can still happen to wood naturally. Preserving wood is normally done worldwide to keep its 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, which is a significant investment.

Step 1: Sanding 

First, we must prepare the wood by sanding it to achieve a 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 must increase measurements. 

You must get a clean cloth dipped in 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 apply a bit of polyurethane varnish to the ends of the wood. Because of the oxygen gaps, the edges of the wood are the most complicated and essential to varnish. 

You will want to remove the masking tape and cover the surface of the wood to prevent the oil from accumulating. 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 a necessary process to improve the product’s durability. To fully harness this strength capacity, you must seal it against potential intruders. Mold, water, and sunlight can be big problems for 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 called 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.

Leave a Reply