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Does Polyurethane Waterproof Wood?

Does Polyurethane Waterproof Wood?

When it comes to protecting your wood from water damage, choosing the right sealant is an important decision. Polyurethane has been a go-to choice for many years due to its ability to form a hard coating that can withstand exposure to moisture. But does polyurethane really waterproof wood? In this blog post, we will discuss the pros and cons of using polyurethane for waterproofing wood and provide useful tips on how best to apply it when needed. We’ll also explore alternative options available so you can make an informed decision based on your particular needs!

PU (Polyurethane)

Polyurethane, commonly known as PU, is a versatile and highly useful material used in an array of applications. PU is a type of polymer that is made by combining a diisocyanate with a compound containing hydroxyl groups. It can be found in foam insulation, car seats, footwear, mattresses, and even in the coatings used to protect hardwood floors.

PU is highly durable, flexible, and resistant to abrasion and chemicals, making it an ideal choice for a variety of structural and aesthetic applications.

Additionally, PU can be formed into molded shapes, which makes it a commonly used material in 3D printing. With its impressive properties and adaptability, it’s no surprise that PU is rapidly gaining popularity as a material of choice in many industries. [1]

Is Polyurethane Waterproof?

Polyurethane is a versatile material that is popularly known for its waterproof qualities. This polymer is created through the chemical reaction of isocyanates and polyols. It is used in various industries, including construction, automotive, and fashion, because of its incredible ability to seal out moisture.

In fact, polyurethane coatings are commonly used to waterproof roofs, decks, and even boats. Polyurethane is also an excellent choice for waterproof clothing, like raincoats, because of its elasticity and durability.

It is worth noting, however, that not all polyurethane products are entirely waterproof, as some have porous surfaces that can allow water to seep through. Overall, polyurethane is an excellent choice for waterproofing due to its sealing capabilities and versatility. [2]

What Makes Polyurethane Water-resistant?

Due to its chemical structure, polyurethane is highly resistant to water. The PU molecules contain long chains of linked compounds that form a network of small pockets or cells. These cells fill with air, which helps prevent any liquid from penetrating the surface and causing damage.

What Makes Polyurethane Water-resistant

Additionally, polyurethane has hydrophobic properties, meaning it repels water by creating a tight seal on the surface. This not only helps protect against moisture but also dust, dirt, and other debris that can cause wear over time.

Furthermore, polyurethane coatings are resistant to UV radiation and chemicals, so they last longer than many traditional waterproofing methods such as paint or lacquer.

Does Polyurethane Protect Wood From Water?

Polyurethane, a type of plastic, can be used as a sealant on wood to protect it from water damage. [3] It forms a tough, protective layer over the surface of the wood, helping to repel moisture and prevent it from penetrating the pores of the material. This can be particularly useful for outdoor applications, such as decking, fences, and furniture, which are constantly exposed to rain, snow, and other forms of moisture. Additionally, polyurethane can also provide a layer of protection against UV rays, which can cause wood to fade and become discolored over time. By creating a barrier between the wood and the elements, polyurethane can help to extend the lifespan of your wooden items and keep them looking great for years to come.

Which is Better: Oil-based or Water-based Polyurethane for Waterproofing Wood?

When it comes to waterproofing wood, you have two main options: oil-based polyurethane or water-based polyurethane. Both types of PU are highly effective at preventing moisture from penetrating the surface of the wood and causing damage, but they do have some distinct differences that may influence your decision. Oil-based polyurethane is a classic choice for adding a layer of protection to wood surfaces due to its durability and resistance to wear and tear. Although this type of PU takes longer to dry than water-based varieties, it forms a hard, glossy coating that can last for many years with proper maintenance.

Oil-based polyurethane is also more resistant to staining and fading than water-based PU, making it a better choice for applications that will be frequently exposed to sunlight. [4]

On the other hand, water-based polyurethane is a great option if you’re looking for a fast-drying sealant with little odor or VOCs. It can also produce a warmer finish than oil-based PU, which may be preferable in certain situations. However, water-based polyurethane does tend to wear away faster and require more frequent reapplication than oil-based products.

Ultimately, it is up to you to decide which type of PU best fits your needs when waterproofing wood!

In conclusion, polyurethane is an excellent choice for protecting wood from moisture damage due to its ability to form a strong, waterproof seal. Whether you opt for oil-based or water-based PU is largely up to your own preferences and the specific application. It is important to remember that proper surface preparation and application techniques are essential for achieving the best results when using polyurethane.

How to Make Polyurethane More Water-resistant?

Although polyurethane is naturally water-resistant, there are a few ways to make it even more so. The first step is ensuring that the surface of the material is properly prepared before applying the polyurethane. This includes removing any dirt, dust, or debris from the area and sanding down any rough edges.

Additionally, using several coats of sealer or primer can help create an additional layer of protection against moisture.

How to Make Polyurethane More Water-resistant

Once applied, you should also consider adding a topcoat of wax or paint to further enhance the water-resistance of your PU items.

Finally, it is important to remember that regular maintenance such as cleaning and resealing are key for keeping polyurethane in great condition over time. With these tips in mind, you can ensure that your polyurethane items stay waterproof for years to come!

How Long Does Polyurethane Take to Dry to Become Water-resistant?

Typically, polyurethane takes 24 hours to dry completely and become water-resistant. It is important to note that this can vary depending on the type of PU used and the temperature and humidity conditions in which it is applied.

For example, oil-based polyurethane typically takes longer to dry than water-based PU, and high temperatures or excessive moisture can further delay drying time. In general, however, you can expect your PU items to be fully waterproof after about 24 hours. [5]

Benefits and Disadvantages of Using Polyurethane for Waterproofing

Before deciding on a waterproofing material, it’s important to consider the advantages and disadvantages of each. When it comes to polyurethane, there are several key benefits that make it an ideal choice for many projects:

  • Durable: Polyurethane is highly resistant to wear and tear, making it a great long-term solution for waterproofing.
  • Easy Application: PU can be applied in just one coat, meaning you don’t have to spend time on multiple applications.
  • Cost-Effective: Polyurethane is relatively inexpensive compared to other waterproofing materials, making it an affordable option.
  • Versatile: This product works well on wood, concrete, metals, and other surfaces, so you can use it for a variety of projects.
  • However, polyurethane also has some drawbacks that should be taken into consideration:

  • Long Drying Time: Oil-based PU takes significantly longer to dry than water-based varieties. This can cause delays when working on a project.
  • Fumes: The fumes or VOCs released while applying polyurethane can be harmful if proper ventilation isn’t provided.
  • Difficulty Removing: If you make a mistake while applying the product, it can be difficult to remove without damaging the surface of the wood.
It is important to weigh all of these factors carefully when deciding which waterproofing material is best for your project.

Overall, polyurethane is an excellent choice for protecting wood surfaces from moisture damage, and is well worth considering for any projects that require waterproofing. With proper preparation and application techniques, you can ensure that your PU items stay looking great for years to come.

How to Waterproof Wood Using Polyurethane?

How to Waterproof Wood Using Polyurethane

Waterproofing wood with polyurethane is a relatively simple process that can be completed in just a few steps.

  1. First, make sure the surface of the wood is clean and free of dirt, dust, and other debris. You may want to use sandpaper to smooth out any roughness or grooves on the surface before proceeding with waterproofing.
  2. Once you’ve prepared the surface, it’s time to apply the sealant. Begin by using a brush or roller to apply an even coat of oil-based polyurethane onto your wooden item. Make sure to cover all areas thoroughly for maximum protection against moisture damage.
  3. Let your first coat of PU dry before applying a second layer. Once the first coat is completely dry, you can apply another even layer of polyurethane to the wood. It’s important to be mindful of drips and runs when applying multiple coats.
  4. After you’ve applied the second coat, let it dry for 24 hours so that it can form a strong waterproof seal on your wooden item.
  5. Finally, use a damp cloth or sponge to remove any excess PU from the surface of the wood. This will help keep your sealed wood looking clean and fresh over time!

By following these steps, you should be able to easily waterproof your wooden items using polyurethane!

Tips How to Protect Wood From Water

Water can be damaging to wood, but there are a few simple steps you can take to protect it from moisture damage.

  1. The first tip is to make sure that the wood is sealed correctly. This means using a sealant such as polyurethane or varnish that will form a waterproof barrier on the surface of the wood. Remember to always apply several coats for maximum protection against water damage!
  2. Additionally, try to avoid exposure of your wooden items to extreme temperatures and humidity levels, as these can cause warping and cracking over time.
  3. Finally, be sure to regularly clean and oil your wooden items in order to keep them looking great for years to come! Regular oiling helps to repel moisture and keep the wood from drying out.

By following these tips, you can help ensure that your wooden items stay in great condition for many years to come!


Is polyurethane a silicone?

No, polyurethane is not a silicone. Silicone is a type of rubber-like material made from siloxane polymers, while polyurethane is an organic polymer made from two different sets of chemicals. While both materials are effective at waterproofing surfaces, they serve different purposes and have distinct properties that make them more suitable for certain applications than others.

Can you apply polyurethane over paint?

Yes, it is possible to apply polyurethane over paint. However, you should ensure that the paint is completely dry and free of any debris or dirt before applying the PU. Additionally, if the painted surface is glossy, it may be best to use an oil-based polyurethane instead of a water-based variety for better adhesion.

Is Polyurethane Completely Waterproof?

No, polyurethane is not completely waterproof. While it does offer some amount of water resistance, it is not a fully waterproof material and can become saturated over time with prolonged exposure to moisture and high humidity. Because of this, many people prefer to use a combination of polyurethane products along with other sealants or protective coatings in order to ensure complete protection from water damage.

This is especially important for items that will be exposed to a significant amount of moisture or may need extra protection against the elements. When using multiple layers of protection together, make sure that each product’s instructions are followed precisely so as to get the best results possible.

What is the Best Waterproof Finish for Wood?

When it comes to wood, there are many different finishes available that can help protect the wood from water damage. The best waterproof finish for wood depends on the type of wood and its intended purpose. For outdoor use, a sealer or varnish may provide adequate protection from moisture in wet climates. For indoor projects, polyurethane is often recommended as a good waterproof finish to protect against spills and humidity.

If you are looking for something more specialized, such as an anti-mold or UV resistant finish, there are also specialty products available.

No matter what your project requires, knowing which product will give your wood the best protection from water is key to creating a lasting result that looks great for years to come.

Will Polyurethane Keep Wood From Rotting?

Polyurethane is a great way to protect wood from moisture damage, however it will not prevent rotting completely. While polyurethane can give added protection against water and humidity, if the wood itself has been damaged by rot or mold, then polyurethane alone won’t be enough to stop the rot from progressing.

Will Polyurethane Keep Wood From Rotting

To really ensure that your wood doesn’t succumb to rot, you’ll need to address any existing issues by repairing or replacing the affected areas before applying a protective coat of polyurethane.

Will Rain Ruin Polyurethane?

Rain can be a damaging force to polyurethane. Excessive exposure to moisture can cause the material to swell, discolor, and even delaminate in some cases. The effects of rain on polyurethane depend largely on how well it is sealed and the quality of the material itself.

If you have outdoor furniture made from polyurethane that is exposed to frequent rain, you should ensure that it is properly sealed or coated with a waterproof sealant so as to minimize damage.

Generally speaking, if you keep your outdoor furniture covered when not in use (either by moving it indoors or using an outdoor cover) and seal it regularly, then your polyurethane should be able to withstand exposure to moisture from rain.

Will polyurethane prevent water rings?

Yes, polyurethane is an effective way to protect furniture from water rings. Polyurethane is a type of finish that forms a protective layer over the wood and prevents moisture from penetrating into the wood’s surface. Applying polyurethane can help prolong the life of your furniture as it will better resist wear and tear caused by spills or daily use. It also helps prevent stains, scratches, fading, and discoloration.

Moreover, polyurethane seals off any existing water rings already in the wood so they won’t get any worse over time. To get the best results, apply multiple coats of polyurethane with sanding in between each coat to achieve a nice even finish.

What Can Damage Polyurethane?

The durability of polyurethane is one of its primary benefits, but it’s still vulnerable to some common contaminants and sources of wear. Direct exposure to UV light can cause discoloration or fading over time, while oils, greases, solvents and other chemicals can also damage the surface.

What Can Damage Polyurethane

The material is also sensitive to extreme temperatures; prolonged heat exposure can cause cracking and brittleness in the finish. Similarly, cold temperatures may lead to embrittlement or loss of resilience.

Polyurethane should not be exposed to abrasive cleaners as this will reduce the life span of the material significantly.

Proper maintenance and cleaning with a non-abrasive cloth will help keep polyurethane surfaces looking great for a long time.

How Do You Waterproof Wood Naturally?

There are several natural methods you can use to waterproof wood. Many of these involve using ingredients such as beeswax, linseed oil, and boiled linseed oil. This section will discuss some of the most popular and effective ones:

  1. Beeswax – One of the oldest and simplest methods for waterproofing is to mix beeswax with turpentine or boiled linseed oil, and then brush the mixture onto the wood. The wax forms a protective layer that repels water and reduces cracking and splitting. It also helps protect against fungus growth.
  2. Linseed Oil – Another common method is to apply raw or boiled linseed oil directly to the surface of the wood to form a seal. Boiled linseed oil is heated with additives to make it more liquid and to allow it to penetrate deeper into the wood. It also helps protect against fungal growth and provides some waterproofing.
  3. Tung Oil – This is a type of oil extracted from the seeds of the tung tree. It has natural water-resistance properties and is often mixed with beeswax or boiled linseed oil to provide an extra layer of protection against moisture. It’s also resistant to mildew and fungi growth.
  4. Coconut Oil – This is another natural waterproofing method that requires regular application for best results. Simply rub coconut oil into the wood, let it soak in, then buff it off with a soft cloth. Coconut oil won’t prevent water from entering the wood, but it will help reduce swelling and splitting due to moisture exposure. No matter which method you choose, be sure to properly clean and dry the wood before applying any protective coating.

Does polyurethane fade in the sun?

Yes, polyurethane can fade in the sun. Polyurethane is a type of plastic material that is particularly vulnerable to UV light exposure and will eventually become discolored or brittle when exposed for long periods of time. To prevent this from happening, it’s best to apply a clear sealant or varnish over the top of the polyurethane before exposing it to direct sunlight. This will provide an extra layer of protection against fading, discoloration, and potential cracking.

Additionally, you should also move furniture indoors or use outdoor covers whenever possible to further protect the material from UV damage when not in use. With proper care and maintenance, your polyurethane furniture should last for many years

What is better than polyurethane?

Some other options that may be better than polyurethane for waterproofing wood include varnish, shellac, and tung oil. Varnish is a great option if you’re looking for a glossy finish that will protect your wooden items from water damage. Shellac is another popular choice due to its ease of application and durability when exposed to moisture. Finally, tung oil can be used as an all-natural alternative to polyurethane but it may not provide the same level of protection against water damage. Each option has its own unique benefits so it’s important to choose the one that best meets your needs!



To summarize, using polyurethane is a great option when it comes to protecting your wood from water damage and will form a hard coating that can withstand prolonged exposure to moisture. Be mindful of the potential disadvantages in some cases and consider alternative options when needed for best results. Taking the time to understand how each type of sealant works in different scenarios and what elements you need for a successful waterproofing project will help ensure you get the most out of your investment.

We hope this blog post has provided helpful information and tips on how best to apply polyurethane as well as other options available. Now it’s your turn, be proactive and start researching products now, so that you’ll be ready when the time comes!


  1. https://onlinelibrary.wiley.com/doi/10.1002/pi.6441
  2. https://knowledgecenter.mearthane.com/polyurethanewaterproof#:~:text=The%20short%20answer%20is%20yes,compared%20to%20other%20known%20materials.
  3. https://www.bobvila.com/articles/how-to-waterproof-wood/#:~:text=Polyurethane%2C%20varnish%2C%20and%20lacquer%20are,sealants%20with%20excellent%20waterproofing%20properties.
  4. https://tallesttree.com/blogs/news/what-you-need-to-know-about-polyurethane-wood-finish
  5. https://www.diygeeks.com/is-polyurethane-paint-waterproof/