How Long Does Polyurethane Last? Know The Correct Answer!

Polyurethane works as a shield for wood materials, especially for indoor use. But most people are not aware of its durability. 

So, how long does polyurethane last? Oil-based Polyurethane lasts 10 to 20 years in a wooden substance. The intact one can last 3 to 6 years, and an opened one can last more than 12 months, a maximum 2 to 3 years with high maintenance. Likewise, a water-based one can last in wood for 10 years and an intact one can for 3 years. But if the can is open, it will last up to 12 months.

You can get more information related to its shelf life. Also, we had a broad discussion about its storage techniques. Stay with this article if you have quarries.

How Long Does Polyurethane Last in Wooden Materials?

Polyurethane is used to protect the wood for a long time. If it does not last for a long time, buying that product would not be worth it. So, let’s see how long it lasts on wooden materials.

How Long Does Polyurethane Last in Wooden Materials

Oil-Based Polyurethane

Oil-based polyurethane lasts longer than water-based polyurethane. 

  • Most of the applied polyurethane lasts between 10 to 20 years. If applied professionally, it lasts more than ten years.
  • But it will not last longer if not taken care of the wooden substance. 
  • If the wood is often exposed to water or chemicals, it will damage the coat. 
  • Also, exposing the wood to sunlight for a long time will lose its protective abilities.
  • You need to apply less layer of oil-based polyurethane for coating. Also, it requires less maintenance. But for careless use, ultimately, people damage the coating and the wood.

Water-Based Polyurethane

Water-Based Polyurethane
  • Water-based polyurethane lasts approximately 10 years. Water-based polyurethane needs more coats than oil-based. If you give less or are not properly applied, it will last less. 
  • Also, if a cheaper quality polyurethane is applied, it will last 5-6 years.

Water-based polyurethane is not commonly used as its durability is less. Also, the process of application is harder as it needs more coats. Moreover, longevity matters most in the case of a wooden protector. Water-based polyurethane fails to give long-term protection.

How Long Does Polyurethane Last in A Can?

There is no doubt that a full can is not used after giving a finish to the wooden subjects. You can not throw out the remaining part of polyurethane after one use. Also, you can buy a product for further use. So, how long it lasts as an intact or opened one is also an important thing.

How Long Does Polyurethane Last in A Can

Intact Can

In case you have not opened the can, the shelf life will be longer. If you look around the can, you will find an expiry date mentioned on the can. The date is given both in the oil-based and water-based polyurethane.

In the case of oil-based polyurethane, it lasts around 3 to 6 years from the manufacturer’s date. The longevity is larger because it contains more oil. The oil acts as a natural preservative and keeps the solution lubricated.

In the case of water-based polyurethane, it lasts 3 years from the manufacturer date. It does not last as intact or opened.

Opened Can

If you have used polyurethane once, remember one thing that it will not last long. With proper care, you can increase its shelf life. But that will not be the same as the intact one.

How Long Does Polyurethane Last in An Opened Can

An opened oil-based polyurethane should be used before 12 months. But with high maintenance and proper storage technique, you can extend 2 to 3 years.

An open water-based polyurethane cannot last more than 12 months. With proper storing techniques, you can extend the longevity for a few months. But if you are buying a water-based, try to use most of the part before one year.

How To Increase Polyurethane Shelf Life in Wooden Substance?

No substance can last long without proper care and maintenance. In the case of a wooden substance, polyurethane is the best protector. But you have to take care of the polyurethane also. Some easy tips can increase the shelf life of polyurethane.

How To Increase Polyurethane Shelf Life in Wooden Substance
  • Before applying the polyurethane, make sure there is no water on the wood.
  • Use the best quality polyurethane.
  • Give proper coating of urethane. The inadequate coating can damage the wood and the applied coatings.
  • Dry properly before applying another coating.
  • Carefully use water around the substances. Try not to pour water too often.
  • Try not to expose the surface to chemicals and oil.
  • Do not keep your polyurethane-applied furniture in sunlight for a long time.
  • Apply a layer once every year. It will protect the previously given coats and increase their longevity.

If you follow these things, the applied polyurethane can last more than the mentioned time.

How To Increase An Open-Canned Polyurethane For Long-Time Use?

How To Increase An Open-Canned Polyurethane For Long-Time Use

If you want to use polyurethane for a long time, you have to follow some rules. It needs a few requirements, but all are crucial.

  • After using the desired amount, remove air from the can. You can use clean marbles or stones. Add them into the can until the polyurethane level rises to the lid. Do not leave any air inside because you may find microorganisms in polyurethane if you allow air to pass.
  • You can use a varnish thinner or spirit instead of marbles or stones. But avoid mixing it with the polyurethane.
  • If any of these two are still bothering you, use argon gas. Fill the remaining part with it and seal the lid.
  • You can also place the polyurethane in different containers. That can save the remaining products from ruining.
  • Wrap the lid from the outside with a plastic wrapper.
  • Never shake your polyurethane before using it because it allows air to enter the polyurethane.
  • You should keep the container in a dark and cold place. The basement is a better storage place. Do not let it be exposed to excessive heat or cold; it can freeze or melt.

Following these steps, you can increase an open canned polyurethane lifespan.

How to Tell If The Polyurethane Goes Bad?

There are several ways to find out that the polyurethane goes bad. If you find the following features in your used polythene, dispose of it immediately.

How to Tell If The Polyurethane Goes Bad
  • If you find the texture hard, it is a clear sign that the polyurethane went bad.
  • If the polyurethane is not still harder but changes a little texture, examine it. Pour it on a plain wooden surface. If it is not evenly wiped, it is not good. But if it is evenly wiped, wait and see its drying time. If drying time extends the product’s highest drying time, it is a clear sign of bad polyurethane.
  • Another way of examination is its odor. The smell of polyurethane changes if it goes bad. The odor comes from a bad polyurethane that is not the regular one. It will smell sour.
  • You may sometimes find microbial attacks on its surface. You should not use it then on any substances.

If you find any of these features, stop using that product. A bad polyurethane cannot give any protection; rather, it damages the wood.

If you’re curious about the longevity of polyurethane finishes and how long they last, our guide on whitewood vs pine might also offer insights into selecting the right wood for your project. Additionally, if you’re interested in learning how to apply polyurethane using a rag and need guidance, our article on how to apply polyurethane with a rag could provide step-by-step instructions. We understand the importance of achieving the best finishes and addressing specific application techniques, and our comprehensive resources are designed to help you navigate and make informed choices for your woodworking projects.


These are some commonly asked questions by people about polyurethane.

Q: Can I use Old Polyurethane?

Yes, you can use old polyurethane if it is good for the wood. If the application takes more time to dry, do not apply on the desired substance. Also, if it emits a foul or sour smell, do not use it.

Q: How long until polyurethane is waterproof?

Polyurethane is water resistant. But oil-based polyurethane can act as waterproof for 30 days and water base is for 7 to 14 days.

Q: What is the meaning of polyurethane turned white?

Polyurethane turned white, which means that it is going bad. But that does not mean that you can not use it. Sometimes, after using it, the milky appearance disappeared.


Applied polyurethane can give protection to the wood for a long time. But if you say about the expiry date, you can find it on the can. In case you have opened it, it will not last long. So, after applying polyurethane,  you should do some tasks for storage.

If there is any air remaining, it will damage the polyurethane. The texture will change and the odor could get sour. In that case, you can add stones, marbles, spirits, or argon gas to remove the air. Then, seal the lid. In this procedure, both the oil-based and water-based polyurethane will stay long.