What Is The Difference Between Silicone and Polyurethane Sealant? 

 October 13, 2020

By  Dale Keese

Silicone and polyurethane sealants are the most popular sealants in the market today. They are both formulated with elastomeric material which keeps air and moisture out while filling in the surface gaps. They are similar in many ways, though many people still wonder which of these to use.

The difference between silicone and polyurethane sealants is in their chemical composition: silicone is inorganic while polyurethane is organic and less chemically resistant. These are the primary differences of each of their sealants, which affect their lifespan and how quickly they break down.

Because of the difference in their chemical composition, each of these sealants have their own advantages and disadvantages. To better understand if silicone or polyurethane sealant is better suited for your project, let’s get to know each of them in detail.

Sealants are an elastomeric material which allows for movement on the surface it is applied on. They’re used in building materials to prevent moisture and air, and aside from this important function, they also lend cosmetic improvements to the surface they’re applied on.

Silicone and polyurethane are the most widely used choices among sealants. Although they do work the same way, their chemical composition affects various aspects of its performance as well as cost. These are important things to consider when choosing between the two types of sealants.

Drying time 

Silicone dries much faster than polyurethane. On the other hand, polyurethane tends to stay wet for as long as 24 hours. This is why silicone is rarely ever used in areas prone to high vehicular or human traffic, whereas polyurethane would be a better choice because it resists abrasion much more effectively.

Weather resistance

Silicone is recommended for use in colder climates because it has no impact on the application. Polyurethane is more difficult to apply the colder the temperatures are. Silicone is flexible even in lower temperatures, unlike polyurethane.


Silicone sealants are best used for tile, glass, or metal surfaces. Polyurethane is recommended for concrete, masonry, and natural surfaces including wood. Since polyurethane dries hard, application should be much swifter because it stiffens as soon as it gets out of the tube. Meanwhile, silicone is softer which makes it easier to apply and remains soft throughout application.


Silicone sealants have a lifespan of at least 20 years, while polyurethane sealants last 5 to 10 years on average. The factors that affect how long each sealant lasts is how much sunlight it’s exposed to as well as temperature changes, since these impact how often a surface needs to contract or expand. The reason why silicone sealants last longer is because its chemical composition prevents it from breaking down, since it is an inorganic material.

For homeowners, lifespan should be taken into consideration because when you are buying a system replacement, it’s important to consider the warranties. Polyurethane sealant manufacturers typically provide a 5 year warranty, while silicone sealant manufacturers offer a 20 year warranty. You can make a decision based on how long you’re planning to maintain the building. In some instances, warranties may be transferrable to a new property owner.


The price will affect any decision you may have, so here are some more things to consider:

  • Material cost: Silicone tends to cost twice as much as polyurethane
  • Labor cost: The application process for both silicone and polyurethane sealants are similar, but if you are going to outsource labor, repair, or replace polyurethane sealants more often, you’re going to spend much more.

The next time you spot a crack and identify that it needs to be sealed, you now know why there is a large price difference among offers. The cheapest offer may actually result into an expensive problem in the long run. This is why it’s crucial to choose the correct sealant from the get-go.

Frequently Asked Questions

What are the advantages and disadvantages of polyurethane and silicone sealant?

Silicone Pros:

-   High ultraviolet resistance
-   Temperature resistance
-   Possesses the highest movement capability
-   Longer lifespan
-   Stays flexible over time
-   Dries quickly
-   Best for cold temperatures
-   Malleable
-   Long life span

Silicone Cons:

-   More expensive
-   Pure sealants aren’t paintable
-   Strong odor
-   Not ideal for high traffic locations
-   Flammable when in direct contact with flame

Polyurethane Pros:

-   Extremely tough
-   Resistant to abrasion
-   Can be painted
-   Good adhesion
-   Affordable
-   Good movement capability

Polyurethane Cons:

-   Difficult to apply
-   Longer drying time
-   Not suitable for cold weather
-   Shorter lifespan

Can I transition from one type of sealant to another?

Yes. To transition from either kind of sealant to another, you’ll need to make sure that all previous sealant applications are completely removed first. If you apply one type of sealant over  another kind of sealant, this will cause quick deterioration and it will end up damaging the seal. It will also prevent you from having a smooth, seamless application as you may notice thick beading and cracks in the caulk.

More often than not, it costs more money to replace a deteriorated sealant than to install it correctly on the first try.

Is polyurethane or silicone sealant better for concrete?

When it comes to concrete projects, whether it’s in the outdoors, a driveway, or pavement, it needs to be able to expand and contract without cracks that tend to form once water gets underneath the surface.

This is why you need to fill the expansion joints with material that eliminates the possibility of water seeping through. Either silicone or polyurethane sealants can do the job. However, the chemical composition of polyurethane sealant is better suited for sealing porous surfaces including concrete.

But if you are merely looking for a short-term sealant meant to add protection to a concrete surface such as walls, silicone sealants are recommended. Keep in mind that you would have to reapply silicone sealants regularly over time. Silicone sealants are also used if it’s more important to preserve the concrete’s look since it penetrates deep into the surface and won’t alter its appearance.

Is polyurethane sealant waterproof?

Yes, polyurethane sealants are waterproof. As it’s recognized as a highly versatile sealant, it’s commonly used to waterproof surfaces in both residential and industrial applications on concrete, masonry, plastic, vinyl, and metal.

Is silicone sealant waterproof?

Yes, silicone sealants are waterproof. It’s widely used for projects that require a tight waterproofing seal such as bathrooms (sinks, tubs, toilets, faucets) as well as aquariums, metal pipes, or other types of metal fabrication. When applied correctly, silicone sealant can provide a protective and waterproof seal for as long as 20 years but its lifespan and waterproofing capabilities may degrade with time especially when exposed to extreme temperature changes.

About the author

Hey, I'm Dale Keese.. thanks for reading.. hopefully this article can save you some time and trouble with your sealing job. I'm also in the process of making some video walk-throughs for youtube so check back soon! thanks

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