How to Waterproof Wood for Bathrooms, Outdoors, and Other Places

Wood is the oldest and most popular construction material in the world. And although it is highly versatile and durable, it can get damaged and disfigured on exposure to bright sunlight, humidity, wind, or rain.

To protect your wooden furniture or the wood in your flooring, doors, windows, or walls, you need to waterproof it. And if you intend to place wooden furniture outdoors, you should perform complete weatherproofing instead. 

Waterproofing or weatherproofing increases the longevity and durability of wood by creating a tough layer over the wood through which water cannot seep in.

In this guide, we will focus on how to waterproof wood for indoor as well as outdoor spaces. 

Continue reading to find out more.

For more woodworking tips, read our Woodworking 101 guide.

Ways to Waterproof Wood

There are several ways in which you can waterproof wood. These methods can be split under three categorical headings:

1. Using Oil

Hand-rubbing oil over the surface of the wood is a tried and tested technique of waterproofing it. 

Oil is generally suitable for treating smaller surfaces such as tables, kitchen countertops, and others. For projects involving a larger surface area that needs to be treated, it is good to go for a stain or sealant.

These are the steps involved when using oil for waterproofing wood:

Choosing the Oil

You can pick from one of these three oils that are most commonly used to waterproof wood:

Linseed oil

Linseed oil is readily available in two forms, raw and boiled. Boiled linseed oil has metal drying agents. These are poisonous and render linseed oil unfit for use in kitchens or anywhere near the dining area. But it can be used for outdoor furniture.

Walnut oil

Walnut oil is also freely available for purchase from most department stores and it won’t cost you a lot. Be careful of nut allergies though. It is best to know if any member of your household is allergic to walnuts before you decide to use walnut oil for waterproofing wood.

Tung oil

Tung oil is commercially used as a mix in several waterproofing products. Raw tung oil can be quite expensive as compared to other oils though. For this reason, it is normally used in small-scale projects.

Purchase the oil that you find suitable to your needs and buy it in sufficient quantities. Even if some of it is left over after the work is finished, you can save it for future projects as oil has a long shelf life.

You might be interested in: How to Distress Wood? 11 Easy Ways for Woodworkers

Mixing the Oil

Blending the oil with other ingredients is recommended before you can use it as an effective waterproofing solution. This speeds up the process of drying and also reduces the stickiness of oil, besides creating a longer-lasting finish. Having said that, you can always use the oil as it is, that is, without mixing in any other solution into it.

Although there are pre-blended oils available for purchase, you can save a few bucks and make a custom mix on your own. Here is how to do that:

• Use one part oil and mix it with equal part turpentine oil. To this, add a half-part apple cider vinegar.
• Mix these fluids thoroughly in an empty container.
• Another way involves mixing two oils (usually linseed oil and tung oil) in one part each. To this, one part mineral spirit and one part polyurethane are added.

Preparing the Surface

You must have a smooth work area before you can apply oil over it. If the surface has irregularities and rough patches, it will be more visible when oil is applied.

You can prepare the surface by using the following techniques:

• If the work surface is small, you can use sandpaper to manually sand it.
• For large surfaces, it is better to use an orbital sander or a belt sander.
• Finish the sanding with subsequently finer grit sandpaper. This will give a smoother feel to the wood.
• Sweep up the residue dust with a clean cloth or vacuum the surface to prepare for the next step.

Applying the Oil Blend

This can be done by either using a brush or a clean and soft rag. To have more control over the pressure you use while applying the oil, using a cloth is a better option.

If you use a brush:

• Apply the oil to the wooden surface with a natural and soft-bristle brush.
• Always apply the brush strokes with the grain and in the same direction for all your strokes.
• Use even pressure when you apply the oil.
• Let the oil seep in for about an hour. Then, using a clean cloth, rub the remaining oil into the surface.
• Make sure that all the oil is removed from the wooden surface.

If you use a piece of cloth:

• Fold the cloth upon itself once or twice depending on the size of the cloth. This ensures that there are no rough edges and also allows you to hold the cloth firmly.
• Wear gloves to prevent your hands from getting in contact with potentially irritating turpentine oil or mineral spirits.
• Start by applying a small amount of oil on the rag and rub it on the wood, going with the grain as you do so.
• Work till there is no residual oil on the wood and you get an evenly coated surface.
• Let the oil dry for a while after removing the excess oil.
• You can wait for a day before applying another coat as this will allow the wood to better absorb the oil and result in more efficient waterproofing.

Sanding the Surface

When the wooden piece or surface is completely dry, use very fine steel wool or fine-grit sandpaper to lightly sand it for a smooth finish.

2. Using a Sealant

Artificial sealants are a popular and reliable waterproofing solution. Sealants provide a deep and richly coloured finish to the wood.

These can come in the form of lacquer, varnish, and polyurethane. Most sealants are available for purchase specific to the surface to be finished.

The steps involved in using a sealant to waterproof wood are:

Picking a Sealant

Sealants can be picked up from home improvement stores and the type of sealant you choose will depend on which surface you intend to use it for. For instance, there are deck sealants, furniture sealants, outdoor sealants, and fence sealants.

Since you need to use the sealant for purposes of waterproofing or, better yet, weatherproofing (in the case of outdoor furniture), you should use a marine wood sealant. It is water-resistant and UV-resistant.

Preparing the Surface

If the wood has been finished in the past, it helps to remove the finish completely before you can proceed to apply a sealant. Use large-grit sandpaper, either manually or through an electric sander, to rid the wood of any trace of a previous finish.

Areas that are tough to smoothen can be dealt with by using rougher sandpaper. Always finish with fine-grit sandpaper for an even finish.

Remove any dust particles or waste from the sanding surface with a clean cloth or a vacuum cleaner before you apply the sealant.

Bonus Read: How to Remove Paint From Wood? 4 Ways That Work

Applying the Sealant

Go through these steps to apply a sealant:

• Use a soft-bristle paintbrush or a paint sprayer to apply the sealant.
• Apply an even coat over the entire surface.
• Ensure an optimum range of temperature and humidity in the work area, else the product will evaporate quickly.
• Let the surface dry for a few hours.
• Lightly sand the dried surface using ultra-fine steel wool or fine-grit sandpaper.
• Apply a second coat of the sealant. If the wood is cedar, redwood, or pine wood (softwoods), it might need a third coat for proper waterproofing.
• Allow the wood to sit for some days. This is known as curing and helps the wood absorb the sealant thoroughly.

3. Using a Combination of Stain and Sealant

This is a good option when you are not sure of how to waterproof wood for outdoor use. Stain-sealant combos not only add a touch of shade to your wood but also offer good waterproofing abilities. Plus, they are easy to apply and maintain.

Usually, sealants are water-based while stains are oil-based products. The following steps are necessary for properly staining and sealing wood and for achieving waterproofing:

Choosing a Stain

For most purposes, an oil-based semi-transparent stain is the right choice for treating wood. Depending on whether you want to apply waterproofing stains to your outdoor or indoor furniture, you can choose either an exterior-grade stain or a light stain respectively.

Preparing the Wood

Similar to other waterproofing methods, this one also requires sanding the surface of the wood to remove previous finishes as well as get an even work surface.

• Use steel wool, sandpaper (via manual rubbing or electric sander), or a metal file to rid the surface of any imperfections.
• When using sandpaper, use subsequently finer grits for better finishes.
• Remove all the dust and waste produced as a result of sanding by using a cloth or a vacuum cleaner.

See also: How to Install Hardwood Flooring?

Applying the Stain-Sealant

You will need multiple coats of stain and sealant to achieve the desired level of waterproofing. The steps involved in doing so are:

• Apply the first coat with a paintbrush.
• Ensure an even and thorough application over the entire surface of the wood.
• Allow the wood to dry properly. This can take anywhere between a few hours to a day, depending on the weather and the quality of the wood.
• When completely dry, sand the surface using sandpaper.
• Before applying another coat of stain-sealant, remove sanding residues from the surface.
• Proceed to apply the second coat. This will take longer to dry.
• Check for any stickiness to make sure the surface is completely dry. Dry surfaces are not sticky to the touch.
• When you are assured of the dryness of the wooden surface, you can apply a third and final coat of the stain-sealant.

Waiting for the Wood to Get Cured

You should allow the wood to dry adequately for the waterproofing to take hold. 

Remember, it can take three days or even an entire week for the wood to cure.

Tips on How to Waterproof Wood for Bathrooms

Applying waterproofing to bathrooms is a process filled with unique challenges. Inside the bathroom, wood will be subject to constant exposure to humidity and moisture. To deal with these you need a guided approach.

The following tips can come in handy when waterproofing wood inside bathrooms:

• Ensure that the surface is completely dry before applying a waterproofing solution.
• Always work at room temperature. Extremes of heat and cold can cause your solution to become either too fluid and runny or very thick, which may result in uneven finishes.
• While working indoors, wear a mask to avoid inhalation of toxic fumes.
• If possible, move the work surface outdoors, for the above-mentioned reason.

Conclusion

Waterproofing wood is an essential part of preparing it against future damage by direct contact with water or by a building up of moisture. While you can hire a professional to apply waterproofing solutions to your furniture or other wooden surfaces, doing it yourself will save you some of your hard-earned money while also giving you a valuable experience.

When you are figuring out how to waterproof wood, you might have various doubts about the process as well as about how difficult or easy it can be. This guide seeks to explain the entire process of applying a suitable waterproofing solution for wood, whether indoors or outdoors. 

For this, we have outlined the three main methods used in the process. We hope that the information will help you get a long lifespan out of the wood at your home.

Also read: How to Kill Mold On Wood?