How to Waterproof Wood for Bathroom Floors, Walls, and More

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Skipping waterproof wood in your bathroom can be a recipe for disaster. It might result in mold and mildew as well as warping wood on your bathroom floors and walls. These problems not only undermine the structural integrity of your space but also present health risks to you and your loved ones.

To avoid this costly and risky mishap, I’m going to share how to waterproof wood for your bathroom for ultimate durability and protection.

How Does Wood Waterproofing Work?

This is a process of treating wood to make it resistant to water damage and decay. Wood is a porous material that absorbs moisture, leading to swelling, warping, and rotting. With waterproofing, the wood will prevent these problems by creating a barrier that repels water.

bathroom wooden tiles

It works by creating a barrier that repels water and prevents it from penetrating the surface of the wood. It also helps to protect the wood from damage, decay and rotting caused by moisture.

Benefits of Waterproofing Wood in the Bathroom

Prevents Floor Damages

Exposure to moisture and water poses a risk to wood flooring, as the wood can absorb the moisture and become distorted or warped. If the flooring dries and shrinks to its original size, it may crack or become misshapen.

Ease of Cleaning and Maintaining

Keeping them clean is easier due to their non-absorbent nature, making maintenance a simpler task. Moreover, wooden floors treated to resemble weathered wood also exhibit resistance against different types of wood stains.

Improves Durability

Wooden flooring is known for its durability, with some types, like hardwood floors, capable of lasting a lifetime. Additionally, applying weatherproofing measures can significantly extend the floor’s lifespan, allowing for long-term use with minimal upkeep required.

Refinishing Options

Wooden floors, much like concrete floors, can be revitalized with a fresh coat of paint or stain, which can be easily accomplished on your own. This is a great way to give your floors a new lease of life.

bathroom

Aesthetic

Wooden floors can add elegance and warmth to any space. Additionally, wooden floors can create an illusion of a larger space, which can be particularly important in small bathrooms.

Types of Waterproofing for Wood

Water-Based or Oil-Based?

Water-based options are not as long-lasting as oil-based options. They require less wood preparation and can even be applied to damp surfaces.

While oil-based solutions have a longer lifespan and can penetrate the wood more deeply, it is not possible to apply them in moist conditions.

Tinted or Clear?

Tinted waterproofing options offer both general and UV protection. As a result, they need to be reapplied or recoated every three years.

wood painted with Minwax Helmsman Indoor-Outdoor Spar Urethane

Conversely, transparent or clear solutions aim to preserve the wood’s natural grain pattern and protect against fading. I recommend reapplying these treatments every two years to maintain optimal protection.

Suggested Reading: How to Fix Water Damaged Swollen Wood Furniture 

Before Waterproofing: Preparations + Materials You’ll Need

Before you start to waterproof wood for your bathroom, it is essential to take the necessary safety precautions and prepare the area adequately. Wear appropriate protective gear to avoid contact with the waterproofing solution and fumes. 

Work in a well-ventilated area to prevent inhaling toxic fumes. Keep children and pets away from the area during the preparation and application process. Prepare the surface, clean it thoroughly, and repair any cracks or damage. 

Materials needed for the project include a waterproofing solution (oil-based poly or water-based, depending on your preference), a paintbrush or sprayer for application, sandpaper, plastic sheeting to protect the surrounding area, tape, and rags for cleaning up spills or drips. 

Method #1: Using Oil for Waterproofing Wood

Step #1: Put on the First Coat

To avoid damaging the wood surface in the process of making wood waterproof, I’d advise against applying oils onto it directly.

Instead, pour the oil onto a rag and use the saturated portion to gently rub the wood, beginning from the interior and working outward. This method ensures a more even application and minimizes the risk of damage.

sponge brush and Rust-Oleum 207008 Marine Spar Varnish

Step #2: Leave it to Dry

I recommend allowing approximately 30 minutes for the oil to penetrate the wood fully. After this, remove the excess oil. The surface should be left to dry for at least 24 hours.

Step #3: Put Two More Oil Layers

Once the initial coat has dried, use a 0000-grade steel wool or its equivalent sandpaper grit to sand the surface before applying two more coats of oil. 

I recommend waiting for 24 hours after the second coat has been applied. After this, spread the third coat.

Step #4: Let it Cure

It is important to allow the surface to fully dry for a minimum of three days, or longer if necessary, until it is completely dry. 

How to Pick the Best Oil for Wood

When picking the best oil to waterproof bathroom wood, consider choosing an oil specifically designed for outdoor use. You must also consider its waterproofing, the type of wood you’re working on and its natural water resistance. 

mixing Minwax Water-Based, Oil-Modified Polyurethane

Consider also the climate and weather conditions in your area and choose an oil that fits your maintenance schedule.

Things to Remember When Using Oils

Method #2: Wood Waterproofing Using Sealants

Step #1: Prepare Your Sealant

Blend the wood sealers thoroughly by stirring for a minute or until it reaches the desired consistency for application. It’s important to adhere to all guidelines specified by the manufacturer.

Ready Seal Wood's Sealer and Stain

Step #2: Put on the First Coat

When it comes to applying a wood sealer, I recommend using a paintbrush and following the direction of the wood grain for the best results. It’s also important to work quickly to minimize exposure to any potentially harmful fumes. Ensure good ventilation in the workspace to further safeguard against these fumes.

Step #3: Dry it

The good news is that the initial layer dries relatively quickly within 4-10 hours, which allows for applying the first coat in the morning. Afterward, apply the second coat later in the evening.

Step #4: Apply the Second Layer

After the initial layer has dried, it is important to use fine-grit sandpaper to clean the entire surface and improve adhesion before applying the subsequent layers. Typically, hardwoods require only one or two coats, while softwoods necessitate at least two.

Step #5: Let it Cure

To determine if the wooden bathroom floor has fully cured, observe if water runs off the surface  and beads up instead of being absorbed into the wood.

Picking the Right Interior Waterproof Wood Sealant

Varnish

When selecting a varnish for interior pieces such as coffee tables and end tables, a spar varnish is a suitable option to prevent unsightly cup rings. For exterior wood that will be exposed to the elements, opt for a marine varnish that includes UV absorbers.

sealing wooden tiles

Lacquer

On lighter woods, lacquer may develop a yellowish hue deemed unappealing. However, lacquer produces a lustrous, warm, and highly scratch-resistant finish on dark-toned woods. To achieve optimal results, apply several light layers of lacquer.

Epoxy Resin

Although this is not a common choice, epoxy resin is highly effective in providing long-term protection for luxury bathroom surfaces.

Important Things to Remember When Using Sealants

Method #3: Waterproofing Wood Using a Stain and Sealer Combo

Step #1: Ready the Stain-Sealant Mix

Measure the amount of varnish needed for the whole project and transfer it into a sizeable container. Gradually add the stain in small amounts and wait for the mixture to transform into a hue that falls between the varnish and the stain.

Ready Seal Wood's Sealer and Stain- Natural Cedar

Step #2: Apply the First Layer

You’ll need either a paintbrush or a paint roller for the application. Once you’ve chosen your tool, immerse it into the mixture and carefully apply it onto the wood, following the grain’s direction. The goal is to achieve a smooth and even distribution across the surface.

Step #3: Let it Dry, and Wipe Excess Stain Off

Once your piece turns into a dried wood surface, use fine-grit sandpaper to sand the rough surfaces, and then wipe it down with a lint-free cloth in preparation for the second coat. 

Moreover, the drying time for a stain-sealer ranges from four hours to a whole day, depending on various factors, including weather conditions.

Step #4: Apply the Second (to Third) Layer of Coat

When applying the second coat, adhere to the same principles as when applying the initial coat, taking even more care to avoid spreading the mixture too thinly. Once completed, allow for approximately five hours to one day of drying time before applying the third and final layer.

Step #5: Let it Fully Cure

Following the application of the final coat, it’s crucial to allow the surface to cure for a minimum of three days before using it. Test the surface after 73 hours to ensure it’s fully cured. If water droplets are repelled, then the surface is good to use.

installing wooden tiles

Recommended Stain for Wood Floor Waterproofing

Since bathrooms are exposed to high levels of humidity and water, an exterior-grade wood stain is necessary. Consider also the tone of the wood stain, which ranges from light to dark. 

Typically, the lighter wood stain has higher oil content and is more suitable for indoor applications or woods that aren’t exposed to humidity. Darker wood stains, such as teak sealant, are better suited for bathroom floors. 

Finally, using pre-mixed stain-sealant products can save you time, effort, and confusion during the mixing process. Alternatively, you can mix the two components yourself using marine varnish.

Why Opt for a Stain-Sealant Combination?

Stain-sealant combinations that provide waterproofing properties are optimal for achieving effective waterproofing while also enhancing the aesthetic appeal of the wood. 

They are available in various colors, and the pigments used to create these colors are typically combined with binders such as water, oils, or alkyl-based binders.

Olympic Elite Advanced Solid Color Stain and Sealant in One

These are designed to be absorbed into the wood upon application and do not typically accumulate on the surface, meaning there is no need to wipe away any residue. However, alkyl-based stains may leave behind some residue on the surface.

Tip in Using a Stain and Sealant Combination

Method #4: Waterproofing the Bathroom Wood with Resin & Acetone

Step #1: Prep the Mixture

To waterproof wood for your bathroom using this method, begin by preparing the resin and pouring enough into a container. Next, gradually mix in a few drops of acetone until the consistency feels slightly thicker than water. 

mixing Ready Seal Wood's Sealer and Stain

If the mixture seems too thin, add more resin until it reaches the desired thickness.

Step #2: Apply the First Layer of Coat

To complete this process, you will require a paintbrush or paint roller. Take either the roller or brush and moisten it with the mixture, then proceed to gently apply it.

Step #3: Dry it

When applying resin-acetone mixtures, it is necessary to wait approximately 30 minutes between each coat.

Step #4: Apply the Second (to Third, Fourth, Etc.) Layer

Generally, it takes approximately five coats to achieve optimal water resistance for wood. Exercise caution when applying subsequent coats to avoid causing damage to the previous layers by applying too much pressure.

sealing wood after staining

Step #5: Let it Cure

Allow the surface to dry completely, which typically takes a minimum of six hours, although I advise leaving it overnight. Before using the wood, test it by splashing a small amount of water. If the wood remains unaffected, then it is ready for use.

Choose the Right Resins for Waterproofing

To begin, it is essential to use polyester resin specifically designed for wood applications. While synthetic resin, dissolved tree resin, and polyurethane resins are also available, the last of the three is the most commonly used option.

Polyester resin can be divided into two categories: laminating resin and finishing resin. Laminating resin is generally applied over sealers. On the other hand, finishing resin can be used without a wood sealer. 

pouring epoxy resin

Finishing resin contains additional wax, which allows it to harden and create a wear-resistant surface, while it also dries faster than laminating. Laminating resin requires a longer drying time but will result in a softer surface.

Waterproofing Wood For Bathrooms In Different Areas

Bathtubs

1. Put a small amount of silicone caulk onto a tool, such as a caulking gun, and spread it evenly along the line where the tub and wall tiles meet.
2. Apply a thin layer of silicone caulk around the drain and any other fixtures with gaps between them and the tiles. Spread it evenly and make sure all gaps are filled.
3. Purchase a high-quality, self-adhesive waterproof membrane from the market. Place the waterproofing membrane underneath the cement backer board before installing the tiles. Make sure to follow the instructions provided in the manual for proper installation.

Countertops and Cabinet Interiors

1. Take a silicone caulking gun and apply a good amount of silicone caulk along the inside edge of countertops and cabinets

counter top with resin surface

2. Use silicone caulk to seal any gaps around faucets, sinks, and other areas where water could enter. Make sure the caulk is applied evenly, and all gaps are filled.
3. Purchase high-quality epoxy compounds that can be easily applied using a brush or an applicator gun, depending on their viscosity. Epoxy compounds are ideal for filling large holes in concrete walls before laying tiles.
4. Allow enough time for the waterproofing compound to dry and cure before laying tiles and grout. Apply the compound well ahead of time, at least two days before laying the tiles and grout.

Walls or Floors around Showers or Bathtubs

1. To prevent water damage, it is necessary to apply first a waterproofing compound to the walls surrounding tubs and shower walls.
2. It can be applied using a brush or roller, based. Unlike other types of sealants, it does not require any priming. However, it is important to wait for at least two days before tiling over the surface. 

bathroom hardwood floor

3. Waterproof paints are suitable for painting wood areas prone to leakage, such as bathrooms and kitchens, as they waterproof the surface and enhance its appearance, simplifying maintenance. Nonetheless, as these paints are thicker than impregnating compounds, it is essential to wait at least three days before tiling over them. 
4. Before laying tiles and grout, make sure to prevent any water from seeping through for at least two days.

Recommended Wood Types for Bathroom Walls & Floors

Solid Hardwood

Solid hardwood floors are naturally water-resistant woods due to their natural resins and oils. They can be sanded to restore their finish, making them long-lasting and attractive to buyers as a bathroom floor.

Teak Wood

Teak has sturdy properties and does not need frequent varnishing. Teak oil can enhance its appearance and maintain its durability.

Solid Softwood

Softwoods are unsuitable for bathrooms due to their tendency to absorb water caused by their porous nature and loose grain structure. However, with proper preparation, some softwoods, such as cedar and pine, can still be used for bathroom flooring.

white wooden floor

Cedar Wood

It is highly resistant to twisting, warping, and cracking, making it an excellent choice for modern bathrooms.

Engineered Hardwood

Engineered wood flooring comprises 3 or 4 wood layers that are glued together. This allows for sanding and restoring the floorboards to their original finish in case of damage. They are very stable and more resistant to shrinking and swelling compared to solid hardwoods.

Laminated Wood

The wear layer or protective overlay is highly dependable, with some manufacturers claiming it can last up to 30 years. However, using laminate flooring for your bath is an inexpensive option. Also, it’s important to remember to protect the base wood from moisture.

Reclaimed Wood

To create a distinctive look for your bathroom wood, consider using reclaimed wood panels. This type of flooring is made from timber that has been previously utilized and attached. However, keep in mind that installing reclaimed wood floors can be expensive.

How to Protect Wooden Surfaces from Moisture & Water Inside the Bathroom

Opt for a Water-Resistant Wood

I recommend choosing water-resistant wood for your bathroom flooring and furniture to avoid any potential water damage. Teak is considered the most water-resistant wood, but other options, like cedar and redwood, perform well in damp environments.

Teak wood

Use a Waterproof Finish Consistently

One frequent error people commit is waterproofing their bathroom floor or wall only once and then disregarding it. However, this is a major blunder because even the finest waterproof wood sealant for interiors becomes less effective over time.

Apply Lemon/Vinegar Solution or Oil

This is an effective method to extend the longevity of the water-resistant coating on wood. Despite contradicting common knowledge, this technique helps shield the wood from harm, maintains the wood’s integrity, and provides a pleasant aroma.

Fix Bathroom Issues with Moisture

Repair any damaged pipes and check if your sink is releasing water aggressively. It’s also advisable to consider using a dehumidifier designed for bathrooms to eliminate surplus moisture.

Clean the Floor Regularly

For regular maintenance, I recommend using a vacuum equipped with a floor brush attachment, either weekly or bi-weekly. For a deeper clean, perhaps during spring or just before winter, opt for a diluted wood floor cleaning solution paired with a specialized wood floor mop. Always make sure to promptly wipe down the surface after cleaning to prevent any moisture damage.

How to Tell if Wood is Waterproof: Does Painting Make it Resistant to Water?

Are Pressure-Treated Woods Waterproof?

Pressure-treated wood is not entirely waterproof. During the pressure treatment process, the wood is infused with chemicals that provide some level of protection against water, decay, and insects. 

pressure treated lumber

This treatment process makes the wood more durable and resistant to moisture, but it does not make it completely impervious to water.

What’s the Best Way to Make Plywood Waterproof?

Water-based paint, waterproof varnish, and liquid latex are other solutions worth considering. Among these, liquid latex is particularly convenient as it only requires spraying and doesn’t need much attention afterward. For more details, check this guide on how to waterproof plywood

Can You Find a Waterproof Paint for Wood?

Yes, there are waterproof paints specifically designed for wood. These paints contain special ingredients that make them more resistant to water and moisture, helping to prevent wood from rotting, warping, or cracking. 

FAQ

Can you make wood 100% waterproof?

It is impossible to make wood 100% waterproof because wood is a natural material that can absorb moisture over time. However, various methods can be used to enhance the water resistance of wood and prolong its lifespan.

How do I protect my wooden bathroom vanity?

To protect your wooden bathroom vanity, apply waterproof paint or clear coating. This protects them from the harmful effects of moisture in the bathroom. It prevents issues such as discoloration, rotting, warping, and swelling.

How can you protect wood from saltwater?

Exposure to saltwater can cause significant damage to wood. To protect it properly to prevent degradation, use a marine-grade sealant, or you can apply a coat of varnish or paint.

Can you use oak wood in your bathroom?

Oak is a hardwood that is naturally resistant to water and moisture, which makes it a good choice for use in a bathroom.

Conclusion

Learning how to waterproof wood for bathrooms is essential to prevent water damage, rot, and mold growth. To achieve this, it’s crucial to select the appropriate waterproofing method.

With the right waterproofing approach, wood floors and walls can provide a beautiful and durable design element in bathrooms for years!

robert headshot

Robert Johnson is a passionate furniture maker & carpenter, sought after for his knowledge on the craft.
You’ve probably seen his down-to-earth wisdom in USA Today, Bobvila, Family Handyman, and The Spruce, where he has shared commentary and guidance on various woodworking topics.

Robert is the brain behind Sawinery, where he aims to share tips, tricks, and a passion for all things carpentry.

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