What Is the Best Waterproof Wood Finish (4 options)

Wood is porous and therefore very sensitive to water damage. That is why it is important to treat your precious projects with a waterproof wood finish. Only in this way can you extend the quality and lifespan.

The 4 best waterproof wood finishes are Oil-Based Varnish, Waterproof Sealant-Stains, Polyurethane and Lacquer.
Each of these waterproof wood finishes will form a solid layer on the wood surface that is not only waterproof but in some cases also UV resistant and scratch resistant.

In this article, I’ll take a closer look at these four synthetic finishes as well as how to apply them. If you are looking for how to make wood waterproof, be sure to read this article to the last letter.

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Why is Waterproofing Wood Important?

Before we get to discussing the best waterproof wood finishes, it’s good to understand the difference between water resistance and waterproofing.

If the wood is water-resistant, it can withstand a limited amount of water. This will help protect it from minor spills that can be easily cleaned up. However, when water-resistant wood is continuously exposed to water, it soaks into the wood and causes permanent damage.

A waterproof wood finish creates a tough surface that won’t allow water to soak into the wood. Here there is no risk of water ingress. Waterproofing wood is used on, for example, boats or other parts that come into contact with water for a long time.

The reason why waterproofing of wood is important is because wood is a porous material and can absorb water easily. Prolonged absorption of water can lead to a damaged wood structure. The porosity is something that differs between different types of wood and is also called the durability of wood. You can read more about this in my article, A Clear Guide to Durability Classes of Wood.

To make wood more resistant to water and moisture, for example, if you plan to build something outside with wood, it needs to be treated with some kind of treatment. Otherwise, it will eventually warp, crack, discolor or rot.

At the same time, these products will also offer other benefits such as UV resistance and protection against scratches and mold. Knowing how to make wood waterproof is important for extending its life and appearance.

But watch out! However, this does not make the wood completely invincible to the elements. You will still need to maintain finished wood regularly to keep it looking its best. I will come back to this in detail later in this article.

What is the best waterproof wood finish?

Best waterproof wood finish option #1: Oil-Based Varnish

Oil-based varnishes are in my opinion one of the best waterproof wood finishes to apply. In addition to their good waterproofing, these varnishes dry quickly because they contain natural oils, resin and metal driers.

Oil-based varnish works because the oil in the lacquer is absorbed through the pores deep in the wood and the resin only penetrates the surface. Once the resin has cured sufficiently, it creates a clear coat that is durable.

This type of varnish seals wood like no other finish and is therefore used on wooden boats.

But there is also a drawback to this type of varnish. The metal dryer in varnish can be toxic. So never use it to finish things that food comes into contact with. You will find several alternatives for that in my article, What is the Best Wood Safe Wood Finish (All in One Guide).

Best waterproof wood finish option #2: Waterproof Sealant-Stains

Using a sealant-stain combination is another good option when figuring out how to waterproof wood. Thanks to this option, you can apply both a color finish and a waterproof layer.

Sealant stains consist of either oil-based, water-based or alkyd-based binders, and pigments.

In addition to the opaque option, you can also opt for transparent color variants. This type of sealant dries fairly quickly and requires little maintenance.

Best waterproof wood finish option #3: Polyurethane

Polyurethane is a waterproof wood finish similar to varnish and is even more resistant to scratches. Plastic that has been dissolved in a solvent is called polyurethane. Based on the solvent, polyurethane comes in two different varieties. One type of polyurethane is made of oil, and the other is made of water.

Personally, I think water-based polyurethane is better because it dries so rapidly. The wood absorbs the water, and as a result, the grain lifts a little as a result. But you can simply fix this by using 220 grit sandpaper to sand in between the first and second coat. Although oil-based polyurethanes take a long time to dry and solidify, they won’t have this impact.

If you are considering polyurethane, I advise you not to go for the cheapest option. Cheaper versions contain a lower quality polymer resin which gives them a more plastic feel and look.

Best waterproof wood finish option #4: Lacquer

Lacquer is the last in this list of waterproof wood finishes. It is a quick drying finish that is applied to wood. Lacquers can be sprayed or brushed on. Note: paints may only be applied in an open and well-ventilated area. When you are going to spray them you must wear a gas mask.

Lacquers are made up of synthetic polymers such as acrylic resin and lacquer thinners, which are solvents. Once applied to a wood surface, it cures very quickly, faster than any other finish. Lacquer can reach its full hardness in just 7-10 days.

But there is also a drawback. Paint should be applied in a minimum of 3-5 coats for a durable and waterproof finish. Another problem with lacquer is that it is more brittle than the other waterproof wood finishes mentioned above.

How to waterproof wood?

A waterproof wood finish is simple to apply. The only thing to keep in mind is that the finish coat needs a lot of time to properly cure and become waterproof.

Before you apply any water proof wood finish, be sure you have filled all cracks and holes in the wood. My article, What Wood Filler Is The Best To Use? 3 Types Clearly Explained! will help you to find the perfect filler for your task.

Sand the wood with 80 to 220 grit sandpaper to prepare it for applying a sealant. This will enhance the surface for adhesion by slightly opening up the wood’s pores.

Apply a coat of your finish after sanding, then wipe away any leftover dust. Before adding the second layer of paint, let it dry. You can use up to three layers in the same manner.

Apply one coat of polyurethane or varnish, then wait for it to dry. It needs to be sanded once it has completely dried.

After sanding the first coat, apply a second coat and let it dry. Repeat the process whichever many times you wish to use coats. You must do this in order to give the polyurethane or varnish its optimum strength.

How much should you reapply waterproof wood finish?

Applying a sealer to wood does not mean that the wood will be waterproof forever. The natural elements will cause the previous finish to slowly degrade and wear. So reapplication of wood finishes is important if you want it to last.

Depending on the environmental conditions, you will have to apply a new layer of waterproof wood finisher every year or every two years.

Always check the manufacturer’s instructions for how long they last and how often to reapply. But above all, use common sense and check the surfaces from time to time for signs of cracks or loosening of the waterproof wood finish. If the finish starts to fade or the wood underneath looks gray or dull, it’s time for a refinish.

Then sand the surfaces with 80 to 120 grit sandpaper. Once sanded, simply apply the finish as you would on a new piece. When you’re done, let it harden and the maintenance is done.