How to Waterproof Wood for Bathroom?

Wood is quite often used in modern homes as a sink countertop. Some bathrooms also have wooden flooring as opposed to tiles. But the downside to wooden flooring is the fact that exposure to moisture makes it susceptible to accelerated wear and tear.

So, how can you prevent the deterioration of the wood in your bathroom? How can you waterproof the wood for your bathroom? You should continue reading to know the answers to your questions.

Waterproofing Wood in the Bathroom

Waterproofing all the wood in the bathroom is important so that it lasts longer. You should waterproof the wood if you want it to look its best for the foreseeable future.

Moisture can degrade the structure of the wood. It will cause the wood to become moldy. The mold infestation will start to spread, which can be costly to remedy.

Waterproofing the wood will prevent moisture from piercing through the porous surface of the wood. Here are some tips to prevent moisture from damaging the wood.

1. Wear Protective Gear 

You should wear safety equipment before you go about waterproofing the wood surface. Here are the safety gears you should wear when preparing the surface of the wood.

  • Safety mask
  • Rubber gloves
  • Sturdy shoes
  • Long sleeve shirt

Wearing the aforementioned protective gear is essential to avoid getting yourself hurt when preparing the wood. You can safely prepare the wood surface wearing the above items.

Safety Information: Avoid applying the sealant to waterproof the wood in an enclosed environment. Make sure that there is proper ventilation before applying the sealant. This is important to avoid inhaling harmful fumes of the sealant.

If possible, consider taking the wood outside the house when coating the material.

2. Prepare the Surface

Before using a product to waterproof the wood, you have to first prepare the surface. Use 180-grit sandpaper to sand down the wood. This will remove the paint, seals, and any imperfections from the wood.

You should next use 220-grit paper to get a smooth finish of the wood. Afterward, you should clean the area using a broom or vacuum cleaner. You should also clean the wood using a damp cloth or towel.

3. Apply a Sealant

You must apply a sealant to the wood to make it waterproof. There are different types of sealants you can apply on the surface.

Oil and Lemon Solution

Applying a mixture of oil and lemon can protect the wood from moisture in the bathroom.

This will not just preserve the wood but also add a pleasant smell to the wood. Moreover, a mixture of oil and lemon will remove any stains from the wood.

Just add drops of lemon in tung or linseed oil. Fill the spray bottle with a mixture of oil and lemon.

Make sure to spray the solution directly onto the wood. Wipe it off to remove any stains. The oil mixture will penetrate the pores of the wood making it waterproof and give a nice glossy finish.

Tung oil is preferable over linseed due to a longer curing time. But if tung oil is not available you can use boiled linseed oil to waterproof the wood. The preparation process for both oils is the same.

A gallon of tung or linseed oil is enough for about 400 square feet of wood. You will have to apply at least four coats of the solution. The oil will get absorbed into the wood creating a waterproof barrier.

One downside of using oil and lemon sealant is that the drying time is quite long. You may have to wait between one to two weeks for the solution to dry. The exact time will vary depending on the size of the wood you want to waterproof.

You can also use a thinning agent to reduce the drying time. But thinning is not recommended for weathered or unfinished wood as the solution won’t properly penetrate the wood.

Polyester Resin

You can also apply the polyester resin to make the surface waterproof. A polyester resin has a much shorter drying time as compared to oil. Moreover, it can also be used to restore damaged wood. You can use a finishing resin or a laminating polyester resin.

  • If you want to preserve the warm look of the wood, you should use a finishing resin that contains a wax that hardens on the surface.
  • A laminating resin is recommended if you want to pain the wood while preserving the surface.

The application process for the polyester resin is the same as the oil and lemon solution. You should apply the solution after preparing the surface. You should mix the polyester resin with acetone to create a smooth finish.

Just add the resin to a bucket and gradually add the acetone.

Continue to add the acetone until the solution becomes slightly thicker than water. To avoid diluting the mixture, you should make sure to not put too much acetone.

Use a soft-bristled paintbrush if you are coating a small surface of the wood like the wood surrounding the vanity mirror. For applying on the wood countertop or floor, you can use a paint roller.

You will have to create a new mixture for every coat. You must clean the roller or the paintbrush after each coat. For the best possible finish, it is recommended to wait about 30 minutes before the application of the next coat.

You can also add a few drops of wax to the final coat to give a shiny look to the wood.

Polyurethane Sealant

Polyurethane sealant is another great option to waterproof the wood. The sealant is a mixture of polyurethane and acrylic mixture with different solvents.

The sealant can give an attractively glossy finish to the wood. Moreover, the sealant can give a gentle sheen that will improve the look of the material.


A varnish will provide a nice finish to the wood, while also preserving the material. It is a mixture of solvent, resin, and drying oil, which will help protect the wood.

The mixture will protect the wood from turning yellow due to exposure to moisture.

Spar varnish is recommended for wood in the bathroom as it creates an excellent water barrier. You can apply the varnish on the wooden vanities and cabinets.

Applying the varnish is easy and the drying time is just 15 minutes.

Commercial Sealants 

You can also use a commercial sealant for waterproofing wood in the bathroom. Most commercial sealants available in hardware stores consist of varnish, polyurethane, and lacquer.

Commercial sealants are effective in waterproofing and also giving a rich color to the wooden surface. Moreover, they dry more easily and require less frequent reapplications.

You can use the sealant waterproofing wood both inside and outside the house.

Most sealants are available in the bottle or can. You can purchase commercial sealants with varying strengths and durability.

Similar to other sealants, you have to apply the commercial sealants to a dry and clean wood surface. Use a paintbrush or roller to apply the sealant. Leave the sealant to dry for two to three hours before the application of another coat.

It is recommended to apply at least five coats divided over a period of two days for the best results.

You can apply as many coats as possible until the desired results are achieved. The more coats you apply, the more will be the level of protection.

Some commercial sealants are also available as a spray-on can. The mixture is easy to apply using a built-in spray bottle. You should check the label for the correct method for applying the sealant.


Lacquer is a mixture of alcohol and dissolved resin. You can buy it in a wide variety of finishes at your local hardware store. You should use a thinning agent to dry the sealant faster.

An important thing to note is that the sealant emits strong, toxic fumes. So, you should only apply the sealant by taking the wood outside in the open air. Once the sealant has dried completely, you should bring the wood inside.

Another thing to note required the sealant is that the wood can develop a yellow tinge. It is recommended to use the sealant on deep-toned wood. Using the sealant on light-toned wood will not give the best results.

Final Recommendations

Commercial sealants offer the best results for waterproofing the wood in the bathroom. However, using an oil-based sealant often provides a better finish. In addition, the oil-based sealant is more durable as compared to a water-based commercial sealant.

Each sealant has a different curing time. Resins take just one day to cure. Commercial sealers including varnish take about a week to cure. Oils take the longest to cure often requiring a wait of up to two weeks.

An important point to remember regarding sealants is that they don’t last forever. You will have to reapply the sealant at least once every two years to preserve the wood. Moreover, you should apply four to five coats for the best protection of the wood.

Lastly, you should avoid a hot or cold environment when applying the sealant.

This is important otherwise the sealant won’t dry and settle properly. The sealant should be applied at room temperature. For the best results, remove the wood from the bathroom and apply the sealant outside the house.

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