How to Waterproof Wood for Bathroom- 5 Proven Ways

Wooden bathroom flooring, walls, and furniture are popular among homeowners. But most users are unaware or at least neglect risks water poses to the structure.

Strictures made of wood in the areas that is constantly moist such as bathroom should especially be protected hence the discussion on how to waterproof wood for bathroom.

Here’s how to go about the process:

We have four surefire methods to waterproof bathroom wood. Apply tung or linseed oil to create a lovely and protective hand-rubbed topcoat.

Also, finish and waterproof the surface simultaneously with a stain-sealant combination. Or seal the lumber with a polyurethane, lacquer, or varnish finish.

Finally, apply a resin and acetone mixture to the surface.

These strategies are efficient in protecting the lumber from water damage. All you need is to choose the best one for your project.

Therefore, read this guide for more information on waterproofing bathroom wood.

In addition, we will discuss how to prepare the wood for waterproofing and frequently asked questions on the subject.

Table of Contents

How Do You Prepare Wood for Waterproofing?

Regardless of the waterproofing method chosen, the surest way to ensure an appealing and long-lasting outcome is by excellent preparation.

Remember, any wood imperfections are more noticeable after stain application. The formula also highlights all the lumber stains and colors.

Below is a brief procedure for preparing wood for waterproofing.

  • Wear Protective Clothing

Do not forget to wear safety gear when handling harsh cleaning chemicals and heavy-duty equipment.

For example, always wear gloves when operating power tools.

In addition, put on goggles or safety glasses for protection against wood splinters and dust particles.

Consider an N95 mask to protect yourself from atmospheric bacteria during sanding. The accessory also prevents allergic reactions such as coughing fits and sneezing.

Please avoid walking barefoot, as the floorboard or flooring may have hidden nails.

  • Sand the Wood

Use a metal file or thick sandpaper to remove visible flaws. Scrape the surface until the lumber looks uniform.

Finish by sanding the surface with 220-grit sandpaper. It allows the stain to penetrate the wood evenly.

  • Wipe Wood Dirt and Dust

Before finishing, sweep the lumber or rub scraps with a dry rag. The exercise also fixes hidden damages and flaws that are not visible due to paint coats.

Further, wipe the wood with a water-bleach mixture to remove mold.

  • Allow the Wood to Dry

Examine the walls and floorboards for cracks to fix dampness encouraging bacterial growth.

Wetness also produces foul odors, mildew, and paint or stain peeling. Thus, do a thorough assessment before applying the topcoat.

Moreover, a waterproof seal depends on an oil-free, clean, and dry surface. Hence, let the wood dry thoroughly after cleaning.

  • Tighten Screws and Fill Wood Holes

Tighten loose screws and fill up holes and gaps from nails or screws. Use spackling paste or wood putty for a lasting result.

Also, repair broken wallboards and flooring using nail plates and wood glue.

NB: Test the cleaning agent on a small inconspicuous spot if you doubt its side effects. In addition, its color may change after curing.

Thus, ensure it dries before deciding.

How to Waterproof Wood for Bathroom

Experts give four fail-proof strategies to waterproof bathroom wood where water rules. 

They include oiling the surface, adding a stain and varnish topcoat, waterproofing with a wood sealer, and using resin and acetone. 

All you need is correct application techniques.

Method One: Waterproof the Bathroom Wood with Oil

Bathroom Floor
Wooden Bathroom Floor

First, it is prudent to choose the correct oil for your project.

Further, we have various oil types in the market, available in two primary categories: Penetrating and finishing oils.

Penetrating oils soak deeply into the lumber pores, whereas finishing oils sit on the surface as a coating.

Penetrating oils naturally yellow or darken with age.

But more importantly, they seep deeper into the wood grain. Thus, they prevent moisture from reaching unwanted areas, reducing the risk of rot.

On the other hand, finishing Oils like Tung do not penetrate deeply into the wood pores. 

Hence, when adopting this method, it is advisable to seal the wood with a transparent finish, Varnish, or polyurethane.

The best penetrating oils include tung and linseed oil. They undergo refining to remove chemicals causing yellowing.

Furthermore, Raw Linseed Oil is more famous for exterior applications like decks. It soaks deep into the lumber pores and dries pretty quickly.

But some woodworkers find it harder to handle than Tung Oil. Linseed oil has a longer drying time, requiring some patience during application.

Conversely, Tung Oil dries slower, making it easier to apply to interior projects. However, experts do not find it potent enough for outdoor tasks.

Thus, consider your project needs before choosing the formula.

Nevertheless, both products are available in gloss, semi-gloss, and matte finishes. So, you’ll need multiple coats to deliver a shiny-looking surface like furniture-grade Varnish.

Remember to reapply the oil every few years. It eventually wears out due to prolonged sunlight and weather elements exposure.

Further, please avoid applying penetrating oils on Varnish or polyurethane.

The formulas are designed for smooth coating only. Thus, they will fail when used over textured surfaces.

The application guide is as follows:

  • Wear Safety Gear

Always wear gloves when handling these chemicals and work in a well-ventilated area.

Moreover, wear long-sleeved pants and shirts to minimize skin exposure. These formulas can irritate your skin if you absorb them over time.

  • Create the Mixture

Mix the oil and thinner in the recommended ratio. Usually, you need one part oil and four parts of paint thinner or mineral spirits.

Further, avoid using water as it creates a gel solution. Hence, it’ll be challenging to deliver an even finish with a brush.

  • Apply the First Oil Coat

Spread the mixture onto the wood with a brush. Then, let it soak for fifteen minutes.

Next, wipe away the excess product with a clean rag. This way, you ensure that only a uniform layer remains on the surface.

  • Let the Finish Dry

Wait 24 hours between subsequent layers for the best outcome. But sometimes, water may still bead after three or four applications.

Here, consider a gloss polyurethane coat instead. This way, you seal wood pore gaps more effectively.

Then, allow the finish to dry for one week before applying a second polyurethane layer.

  • Apply a Second Coat If Necessary

Alternatively, you can add a second layer if water beads up after multiple applications. But this time, please use glossy or semi-gloss polyurethane instead of mineral spirits.

Unfortunately, adding polyurethane to your mixture causes yellowing. Thus, test the formula in a small area before finishing the surface.

  • Let Project Cure

Give the project 30 days to cure thoroughly before exposing it to moisture or outdoor elements.

Significant aspects to note about using oils to waterproof lumber include:

  • You can use tung or raw linseed oil for the project and expect a professional outcome.
  • The formulas dry faster than others in the market. And you can mix them with mineral spirits to enhance penetration.
  • Consider polyurethane if the water-resistant project will stay outdoors—raw linseed oil yellows over time with prolonged sunlight exposure.
  • Use glossy or semi-gloss polyurethane for exterior workpieces like decks. It helps to seal the surface against moisture.
  • Utilize a paintbrush for oil-based waterproofing formula.
  • Avoid touching the finish with bare hands to avoid irritation.
  • These oils wear out eventually. Thus, reapply the finish every few years but only after the first year.

Method Two: Add a Stain and Varnish Topcoat

Stain & Varnish is a one-step technique for staining and varnishing lumber. It combines an old-world stain formula with transparent polyurethane.

Coating the stain with a durable transparent finish guarantees a rich color and protects it from fading.

Stain and Varnish also protect the wood from water damage. It does not allow moisture to meet the lumber’s surface, making it waterproof even in the bathroom.

Follow these steps for a successful outcome.

  • Prepare the Mixture (If needed)

Start by mixing two parts of turpentine or paint thinner with one part of paint or Varnish.

Pour the formula into a pump-up garden sprayer or get a bristled paintbrush.

  • Apply the First Coat

Apply the formula using your chosen applicant.

You can spray it on the surface, allowing it to soak in for five minutes. Or apply the solution using the paintbrush.

Ensure you do not overlook corners. They are likely to dampen during showers, causing further damage to your wooden flooring.

In addition, cover all surfaces well and confirm no segment remains untouched.

Lastly, use a roller or brush for more extensive surfaces. Then, let them dry for two hours before going to the next step.

  • Remove the Excess Solution by Wiping

After letting the finish cure for two hours, wipe the wood with a clean paper towel or cloth.

Ensure you remove all excess solution on the surface. Otherwise, it may block wood pores, causing more damage.

Allow the lumber to dry thoroughly before adding another coat.

  • Apply the Second Coat

Apply one more coat if you notice untreated surface areas.

However, ensure no layer remains wet after application. This scenario may create problems during later stages.

For example, the finish will absorb excess moisture and produce damp patches. Worse still, you’ll notice a foul smell even during humidity-free seasons.

Next, if necessary, rub the surface with medium sandpaper or steel wood. And apply another varnish layer.

Also, allow each coat to dry properly before adding more. Continue until you get a satisfactory outcome.

  • Let It Cure

Let the project cure for a week to get a sure waterproofing job.

Alternatively, you can seal and protect the surface with a polyurethane coat.

NB: Stain & Varnish feature fine ingredients that guarantee superior protection. Thus, the bathroom wood remains safe from all kinds of deterioration and damage.

Method Three: Waterproof with a Wood Sealer

A wood sealer is a transparent finish coating the wood’s outer surface. Further, the formula’s primary function is to repel moisture.

Thus, it is beneficial in waterproofing lumber, keeping it safe from rot and fungal growth.

The application process is as follows:

  • Get a Wood Sealer

Bathroom wood is susceptible to stains and scratches, making it look oil-fashioned and shabby.

Thankfully, the water-resistant Varnish is an easy method to prevent these issues. In addition, the finish serves as a barrier between the subflooring and moisture.

  • Prepare the Sealer

Pour some sealer into a paint tray. Then, stir the formula to mix it evenly.

Carefully apply the product over the surface using a lint-free cloth or a natural bristle paintbrush.

  • Prepare the Surface

You can hire an electric sander for this process. But sanding by hand is possible when you have time.

The goal is to ensure the lumber is clean and free from loose material like dust and dirt.

Sweep again with a broom to remove the remaining particles. Then, wipe the floorboard with a damp mop.

  • Apply a Coat of Sealer

Apply the formula uniformly and strive to deliver full coverage.

Watch out for bubbles forming after the solution dries. If they are too many, use a flat accessory like an old credit card or your hand to remove them.

Also, check whether the formula still pools after 20 minutes. Then, wipe it with a paper towel till it soaks into the wood grain.

If necessary, sand the surface again to seal it from moisture damage.

  • Let the Sealer Dry

Give the first coat an hour to dry.

Next, apply the second layer using the above method or spray it with a spray gun.

Please do not let the floorboards become damp after sealing. Allow them at least 24 hours before proceeding to the next step.

  • Clean the First Coat

Wipe the lumber with a clean towel to remove dirt and dust. Then, evaluate the surface for areas with poor overage.

However, don’t worry if you spot any flaws. Repeat the application procedure until you cover the whole surface.

  • Apply a Second Coat

Apply the second layer in a thin coat, not a thick one. In addition, let every coat dry before adding the next.

This way, you prevent clumps and drip accumulation on the surface and guarantee a more uniform finish.

  • Let It Cure

Give the sealer a day to cure before resuming regular use.

This exercise helps lock in the strength of each sealer coat. It also prevents any damage from happening during this step.

Method Four: Use Resin and Acetone

The first step is to get the correct resin and acetone. Moreover, please avoid using acrylic sealers as they only cause problems, not prevent them.

For the resin product, you need one specifically designed for waterproofing wood. And luckily, it is available at any store online or in your area.

Similarly, ensure the acetone does not have anything besides pure acetone. Otherwise, other chemicals react with resin and ruin everything.

Only use acetone when applying water-based wood sealers on concrete surfaces. The solvent-based formula is harmful if you use it outside its intended purpose.

In addition, mix the resin and acetone well before applying them to the wood.

Again, please avoid using nail polish remover with the mixture. It only produces an awful smell and leaves marks on the bathroom floor.

Check out the other application steps below:

  • Create the Mix

The recommended ratio is three parts acetone and one part resin.

Further, use a paintbrush to spread the formula over the bathroom wood. Then, let it dry overnight.

  • Apply the Acetone and Resin Mixture

This step is the most challenging as you have to work quickly. Further, the formula may dry up before delivering adequate coverage.

So, use a foam brush or paintbrush for spreading and a clean rag to wipe off excess formula.

This way, you avoid getting an uneven surface.

Remove stains with acetone-soaked rags until the surface regains its original color.

  • Reapply a Few More Coats

The process needs around 20 minutes to dry thoroughly. However, feel free to scrape resin crystals with a sharp accessory like an ice pick.

Ideally, you need two resin-acetone coats to waterproof the wood desirably.

Sometimes, moisture seeps through the surface after the first coat. Don’t panic but add another one before the solution evaporates.

  • Let It Cure for a Few Days

Check the flooring the following day after applying the formula.

Also, look out for cracks. Then, fill them using carpenter wood filler paste as it evens the surface.

Here’s a Video On Waterproofing Wood for Bathroom:

Importance of Waterproofing Wood for Bathroom

Waterproofing wood has immense benefits.

For instance, waterproofing guarantees longevity despite a bathroom experiencing significant moisture exposure.

Here is more information about the procedure’s importance.

  • Prevents Rot

Prolonged water exposure leads to rot. Moreover, wood rot smells foul, looks ugly, and drastically weakens the material.

If you notice rot in bathroom wood, cut out the area immediately. Then, investigate the cause of the water damage.

Waterproofing wood stops the rot by preventing water absorption.

  • Prevents Dry Rot

Despite being similar, dry rot and rot have different root causes. The good news is waterproofing prevents both scenarios from occurring.

Dry rot occurs when fungi grow on the wooden surface. In addition, it does not need much moisture to thrive.

The damage happens when the lumber dries, but the fungi are already growing thus, the name dry rot.

Consequently, it is crucial to prevent the fungi from growing. And waterproofing makes the strategy a reality.

Waterproofing the wood fills its pores and deprives the fungi of a place to hold on and grow. 

Besides, when moisture hits the waterproof surface, it beads up and drains. Hence, the water does not sit or soak into the lumber.

  • Prevents Splitting

Splitting is among the most damaging effects of prolonged water exposure. It causes the wood to crack and compromises the structure’s integrity.

Sometimes, splitting is challenging to see, especially on installed wood.

But waterproofing comes to your rescue, and you do not have to keep worrying about the lumber.

It prevents moisture absorption and reduces splitting chances.

  • Prevents Mold

Mold and mildew growth is another problem associated with moisture.

Thankfully, waterproofing wood prevents water absorption and hinders mold and mildew growth.

Please note that these organisms are a critical health issue. In addition, they spread quickly, causing severe damage to the bathroom wood.

Furthermore, areas with mold and mildew infestation need cleaning or remodeling. Therefore, take water protection seriously and waterproof exposed wood.

  • Prevents Swelling

Bathroom wood swells as it absorbs water.

Further, a single swelling bout does not warrant lumber replacement. But if the scenario persists, it can destroy the wood.

If you notice swollen wood, examine it after drying. Then, determine if it requires replacement.

Can You Use Plywood In the Bathroom?

Plywood is perfect for bathrooms. Besides, plywood is the go-to material for bathroom subfloors.

However, you can only deliver a durable outcome with the correct product.

Plywood grades depend on the quality of the material’s front and back. Further, faces follow an A to D scale, whereas backs are one to four.

Top-quality plywood is A1 and is the priciest, while a lesser quality product grades A4 and costs less.

So, consider the wood’s grade and cost when choosing suitable plywood.

When purchasing plywood, look for a flat sheet with core layers free from warping. Also, ensure the edges are clean.

Please avoid sheets with lots of voids and knots.

Finally, expect a 1/32 inch discrepancy between the wood’s actual and stated thickness. 

How to Waterproof Plywood In the Bathroom

Plywood is an excellent building material. However, the sheets are not equal.

Further, it is advisable to waterproof plywood if you anticipate prolonged water exposure. This way, you avoid costly moisture damage and repairs.

Luckily, waterproofing the material is a straightforward process. You can also use various formulas ranging from Varnish to oil and waterproofing paint.

As a result, it is practical to keep the surface safe from warping, rot, and splitting.

  • Step 1: Prepare the Plywood

Ready the plywood before applying PVA, paint, or liquid latex. Clean the surface with a dry cloth or brush, removing dirty spots.

Next, use a wood filler for rough spots on the sheet. The exercise gives the surface uniformity and prevents gaps in the waterproofing.

Always give the filler enough time to cure and harden before going to the next step.

Wipe the plywood sheet with a wet rag once you confirm it is dry. Also, the moisture will raise the wood grain, helping the sealer bond better.

The last preparation stage is to sand the surface lightly. Use medium-grit sandpaper, say 60 to 100 grits.

The accessory smooths the sheet and removes rough spots gunking up the sealing or painting.

  • Step 2: Apply the Sealer

Paint the sealer with a roller or brush if you’re using the brush-on sealing technique,

Further, ensure you deliver adequate coverage. Then, let the first layer dry thoroughly before adding the second.

Some formulas and waterproofing needs demand a third coat. Also, although it is not mandatory, having more coats is better.

Alternatively, use the spray method.

Carefully read the manufacturer’s directives. Otherwise, improper use of the spray-on sealer may ruin the project.

For instance, using an inadequate sealer amount delivers spots and blotches. You’ll have more sealer in some areas and minimal in others.

In addition, spray-on sealers are more challenging to control than brush-on products. Therefore, please be intentional when pointing the sprayer to the surface.

  • Step 3: Allow the Wood to Dry, and Keep an Eye

Let the plywood dry for a few hours. However, if you have time to spare, wait up to 24 hours for a better outcome.

Once the plywood dries thoroughly, you can comfortably install it without posing risks.

In addition, add some sealer over nails and screws to ensure it remains watertight.

Further, although the material is waterproof, assessing them every few months is advisable.

This way, you can know if water is wreaking havoc without your knowledge.

Finally, water damage is easy to identify. Therefore, you only need an eyeball test, not a comprehensive inspection.

Here’s How to Waterproof Plywood:

Frequently Asked Questions

Some of the most rampant questions include:

  • How do I Waterproof Wood for Bathroom Use?

First, only apply the chosen formula to dry wood. Otherwise, the finish will eventually fail.

Unfortunately, it is hard to judge whether the bathroom lumber is dry enough to seal. But you can remove it from the bathroom space and let it dry under warm light.

Give the material one day, then apply the sealant.

In addition, it is advisable to work in a room-temperature environment when applying the waterproofing product.

Hot and cold temperatures cause the formula to behave differently, causing it to dry and settle unevenly.

Moreover, please avoid hot and enclosed environments. They make it easy to inhale sealant fumes.

If possible, coat the wood outdoors instead of in the bathroom space.

  • How Can I Protect Wood from Bathroom Moisture?

Protecting lumber from bathroom moisture depends on the available products and intended results.

In addition, it is prudent to reapply the waterproofing sealer after the recommended duration. This way, you guarantee superior protection from water damage.

Below are some aspects to consider:

  • Use an Oil and Lemon/Vinegar Solution

Cut a lemon in half and extract its juice. Continue squeezing until you deliver half a cup.

Next, add 6.5 oz of vinegar to the mixture and stir constantly.

Further, the solution will not affect the wood if water and oil separate. So, ensure all ingredients mix thoroughly before use for the best outcome.

  • Fix Issues at Once

Take a spray container and pour one component at a time.

Add half a cup of the liquid to the spray bottle. Then, pour three tablespoons of mineral oil or vegetable oil.

Close the cover tightly and shake appropriately before use. This way, you ensure uniform distribution throughout the solution’s contents.

Assess the wood surface for mold and mildew and clean it thoroughly before waterproofing.

Remember, dirt residues ruin the protection layer and render your efforts futile.

  • Waterproof Consistently

Use a microfiber or lint-free rag to apply the formula to the wood surface. Further, apply it evenly to facilitate complete coverage.

Oil-based finishes remain intact for up to six months without being washed away by liquids.

Thus, reapply the product frequently to keep the wood safe from moisture damage.

  • Can I Use Wood In the Bathroom?

Wood is a favorite choice in flooring and wall paneling. But it cannot withstand prolonged moisture exposure.

Also, bathroom wood will definitely contact water. Thus, it is prudent to waterproof the material before using it in the bathroom.

The wood swells up due to high moisture and humidity content.

As a result, it will twist and warp during expansion and contraction after installation.

Unfortunately, this scenario is not sightly. Therefore, it is wise to waterproof the bathroom wood.

  • Which Woods Is Best for Bathroom Interior

Manufacturers classify wood from one to five, depending on its moisture resistance abilities.

Class one only accommodates lumber less than 20 percent wet, while class two can withstand moisture levels above 20%. However, the latter only works with limited exposure.

On the other hand, class three wood allows routine exposure to humidity levels above 20 percent, whereas class four lumber can withstand vapor content above 20% and fresh water.

Finally, class five is the toughest lumber type. It can even withstand salty water.

In addition, you can classify wood as hardwood and softwood.

Hardwood materials feature low shrinkage under dynamic and changing conditions. Also, they have superior resistance to fungi, mold, and mildew.

Teak is among the few hardwoods with perfect attributes for a damp area like a bathroom.

Moreover, the lumber has natural non-slip qualities, making it excellent for saunas and outdoor patios.

Teak needs waterproofing but does not require much varnishing for a durable outcome. In addition, it looks better after oiling as it retains its natural properties.

Alternatively, you can use softwood such as Cedar, douglas fir, and pine for bathroom projects.

Further, Cedar wood performs admirably in steamy areas like shower rooms and toilets.

It also features a distinct natural scent and is more reliable than other lumber varieties.

Finally, Cedar’s resilience to cracks, warping, and twisting is first-class. 

In addition, you can use it for any modern bathroom and expect excellent moisture resistance and a historic appearance.

  • Can I Use Wood Flooring in a Bathroom?

Humidity and temperature fluctuation in a shower room or bathroom make the wood susceptible to warping.

Thus, consult hardware or supplier to get a suitable lumber type.

Besides, not all lumber yards supply wood recommended for bathroom projects. But others give specific alternatives.

For instance, engineered lumber is better for bathroom projects, thanks to its nature and tolerance to different conditions.

Also, engineered wood features solid wood layers over ply strips, unlike solid boards from a timber piece.

Hence, you can expect a stable and robust outcome.

Lastly, engineered wood comes in handy for underfloor heating applications. But it is best to consult on the best shower and bathroom floor ideas.

  • Where Can I Use Lumber Flooring in a Bathroom?

Please be more mindful of the wooden floors in the bathroom. Otherwise, pooling water eventually marks and discolors the wood.

Moreover, do not use raw lumber in damp rooms.

Avoid wood flooring, especially in family bathrooms used by kids or anywhere else prone to water splashing.

Also, use a different material for floors with lingering damp towels.

Wood’s natural beauty makes it a perfect choice for bathrooms with keen users. Further, it delivers an excellent antidote to the clinical feel of a ‘tiled all-over pattern.

  • How Do I Maintain Wood Flooring in a Bathroom?

Every product has specific maintenance recommendations. Hence, always confirm with your supplier for accurate information.

Some wood flooring has a Hard Wax Oil to waterproof it.

Therefore, consider reapplying the formula once or twice a year. You’ll feed the wood and improve the topcoat over time.

  • What Wood Lookalikes Can I Use for Bathroom Flooring?

We have alternatives if you’ve ruled out bathroom wood flooring because of the room’s location, household needs, or budget constraints.

Vinyl bathroom flooring ideas deliver an authentic wood appearance. In addition, thanks to today’s technology, some vinyl tiles have a lumber-like texture.

The material is also a perfect non-slip bathroom flooring option.

Alternatively, you can use bathroom floor tiles, such as porcelain and ceramic tiles. They replicate a wooden appearance and are easier to maintain in a busy household.


Waterproofing wood is essential as it increases your project’s longevity.

Further, moisture degrades the lumber’s structures, causing them to become moldy. And worse still, mold infestation is costly to remedy.

So, it is prudent to waterproof the surface to keep it perfect for the foreseeable future. In addition, the exercise prevents water from piercing through the wood’s porous surface. 

Check out some practical tips on:

How to Waterproof Wood for Bathroom

You can seal the wood with a varnish, polyurethane, or lacquer finish, Linseed or Tung oil, a resin and acetone mixture, and a stain-sealant combination.

Fortunately, the above article gives you quick steps on each strategy. Therefore, you can guarantee the durability of your bathroom project.

Image of a woodworker wearing hearing protectors for woodworking

Tyron Otieno

Tyron is an avid woodworker and writer. He founded this website to help other woodworkers, whether hobbyists or professionals by sharing his knowledge and experiencie after a decade of woodworking.

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