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Can Silicone Sealant Be Used Outdoors? How To Apply It Better?

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Can silicone sealant be used outdoors? According to the material properties of different Silicone Sealants, they have different performance capabilities. If you want to find some durable sealants that work really well outdoors, this blog is for you!

Can Silicone Sealant Be Used Outdoors?

Can silicone sealant be used outdoors? Yes, silicone sealant can be used outdoors. Silicone sealant is a type of adhesive that can be used to fill holes and cracks on various surfaces. Silicone sealants are available in different types, including waterproof, solvent-based, and high-heat silicone.

Take DOWSIL 991 Silicone High-Performance Sealant as an example below:

Can silicone sealant be used outdoors

Properties of Silicone Sealant for Outdoor Use:

When selecting a silicone sealant for outdoor use, it is important to choose one that has the following properties:

Weather Resistance:

The sealant should be able to withstand extreme temperatures, rain, snow, and UV radiation without deteriorating or losing its sealing properties.


The sealant should be able to maintain its integrity for an extended period, without cracking or becoming brittle.


The sealant should adhere well to a variety of substrates, including metal, glass, concrete, and plastic.


The sealant should be able to accommodate the movement and expansion of the substrate without losing its bond.

Resistance to Mold and Mildew:

The silicone sealant should be resistant to mold and mildew growth, which can occur in damp outdoor environments.

Chemical Resistance:

The sealant should be able to resist exposure to chemicals and pollutants commonly found in outdoor environments.

Can silicone sealant be used outdoors and what kinds of sealants will be better? Overall, this sealant with these properties can be an excellent choice for outdoor applications, such as sealing windows, doors, and other gaps or joints in buildings, as well as sealing around outdoor fixtures like air conditioning units and light fixtures.

How Long Does Silicone Sealant Last Outside?

The duration of outdoor performance for sealant depends on various factors. Based on the manufacturer's specifications and user feedback, DOWSIL 991 Silicone High-Performance Sealant can provide up to 50 years of durability in various weather conditions, including extreme temperatures and UV radiation.

Factors Affecting the Lifespan of Silicone Sealant

The actual lifespan of silicone sealant may vary depending on several factors, such as:


Proper application of the sealant, including adequate surface preparation and joint design, can contribute to its longevity.

For the practical application of DOWSIL 991 Silicone High-Performance Sealant, the most difficult thing is definitely how to apply it better.

But don’t worry, if you have doubts about this, you can go to Joinstar to get professional answers—they not only provide a variety of high-quality sealants but also provide you with targeted solutions.


The type of substrate and its condition can affect the adhesion and performance of the sealant.


The level of exposure to environmental factors, such as sunlight, rain, and pollution, can affect the sealant's degradation and performance over time.


Regular inspection and maintenance of the sealant can help identify and address any issues before they cause damage.

Overall, silicone sealant can provide long-lasting outdoor performance when applied and maintained properly.

However, factors such as exposure and substrate condition can affect its lifespan, so it is important to consider these factors when selecting and using silicone sealant for outdoor applications.

When Should You Not Use Silicone Sealant Outdoors?

There are certain situations where silicone sealant may not be suitable for outdoor use.

When Not to Use Silicone Sealant Outdoors?

Wet or Damp Surfaces:

Applying silicone sealant on wet or damp surfaces can compromise its adhesion and performance. It is recommended to apply sealant on dry surfaces.

Substrate Incompatibility:

Some substrates, such as some types of plastics, may not be compatible with silicone sealant and may result in poor adhesion or chemical reactions that can compromise the sealant's performance.

For example, for DOWSIL 991 Silicone High-Performance Sealant, we do not recommend that you contact it with natural rubber, EPDM rubber, or certain plastics without proper compatibility testing.

Substrate Movement:

Silicone sealant can accommodate substrate movement to a certain extent, but excessive movement can cause the sealant to fail. It is important to consider the level of substrate movement when selecting a sealant.

Critical Structural Joints:

Silicone sealant is not suitable for critical structural joints that require load-bearing capacity, as it may not be able to withstand the stress and strain of such applications.

Best Time of Day to Apply Silicone Sealant Outdoors:

The best time of day to apply silicone sealant outdoors is when the temperature and humidity are within the recommended range specified by the manufacturer.

This is typical during the cooler hours of the day, such as an early morning or late afternoon, to avoid the risk of the sealant drying too quickly or not adhering properly due to excessive heat or humidity.

Overall, it is important to consider the specific conditions and requirements of the outdoor application when selecting and using sealant and to follow the manufacturer's instructions for the best results.

How Do You Apply Silicone Sealant Outside?

Proper application is essential for the effective and long-lasting use of silicone sealant outside.

Tips for Applying Silicone Sealant Outside

Surface Preparation:

The surface must be clean, dry, and free of dust, grease, and other contaminants that can affect the adhesion of the sealant. Use a suitable cleaner or solvent to clean the surface and allow it to dry completely before applying the sealant.

Joint Design:

The joint design should be suitable for the application and the type of sealant used. The joint width should be appropriate, typically 2-3 times the depth of the sealant.

For DOWSIL 991 Silicone High-Performance Sealant, the ideal ratio of seam width to sealant depth is approximately 2:1. And there should have a backer rod or bond breaker tape installed if necessary.


Apply the sealant using a caulking gun, making sure to maintain a steady and consistent pressure. Use a tool or a finger to smooth and shape the sealant into the joint, ensuring that it fills the entire joint and adheres properly to both sides. 

Final words:

Do you know can silicone sealant be used outdoors and how can you apply it better now? Joinstar can provide you with many kinds of professional silicone sealants suitable for outdoor work! Whether you're looking for house caulk or construction site applications, they're worth the money!