How Temperature Resistance Affects Silicone Sealant Performance

What Is Temperature Resistance in Silicone Sealant?

Temperature resistance refers to a sealant’s ability to maintain its structure, flexibility and adhesion when exposed to heat or cold. Most general-purpose silicone sealants perform well in everyday conditions, but specialised applications—like sealing metal roofs, bathroom fittings or outdoor joints—demand a product that holds up to temperature swings without shrinking, hardening or splitting.

The performance of a silicone sealant is directly tied to its ability to stay flexible. Extreme heat can cause some sealants to degrade, lose grip, or even become more brittle and crack, while extreme cold can make them more brittle. That’s why choosing a product with suitable temperature resistance is key to long-term results.

When Temperature Resistance Matters Most

1. Kitchens and Bathrooms

Heat from ovens, cooktops, kettles and steam can all take a toll on silicone sealant. In bathrooms, the mix of humidity and regular cleaning means you need a sealant that won’t degrade with heat or warm water.

Try: Selleys Wet Area Silicone, specifically designed to resist heat and moisture while providing mould-resistant protection.

2. Outdoor Use

UV rays and high summer temperatures can make standard sealants fade or crack. If you're sealing gaps in walls, metal roofing, gutter joints or around windows, the sealant needs to withstand high ambient temperatures and direct sun exposure.

Try: Selleys Roof & Gutter Silicone, formulated to remain stable and flexible under extreme weather conditions, including high heat. For sealing around concrete or bricks, Selleys Brick and Concrete Silicone is the solution, with Selleys Glass Silicone recommended for use around windows, other glazing, and mirrors.

3. Automotive and Industrial Projects

Engines, exhaust pipes and machinery often operate at very high temperatures. Using a silicone sealant not rated for those environments can lead to premature failure.

Try: Selleys Autofix Instant Gasket High Temperature Sealant, engineered to handle temperatures up to 315°C continuously, and short bursts up to 343°C.

How Temperature Extremes Impact Silicone Sealant Durability

Silicone sealant performance depends on more than just initial application—it needs to stay strong over time. Temperature fluctuations cause materials to expand and contract, and if your sealant can’t move with them, cracks and leaks can form.

For example, under high heat, low-resistance sealants may soften, slump or lose adhesion altogether. In extreme cold, they may shrink, stiffen, or become prone to splitting.

This is especially true for outdoor or semi-exposed surfaces, where temperatures can swing dramatically from day to night. Over time, repeated expansion and contraction will wear out any product that isn’t designed for thermal flexibility.

Tips for Improving Silicone Sealant Performance

Using a product rated for the temperature conditions you expect is essential, but correct application is just as important. Silicone sealants such as Selleys Roof & Gutter Silicone or Selleys Wet Area Silicone will only perform to their full potential if the surface is clean, dry, and free from oil or soap residue.

Preparing the area with a surface cleaner like Selleys Sugar Soap can improve bonding. Applying in cooler weather or late in the day—when surfaces are shaded and not overly hot—also helps the sealant cure evenly. For exposed or high-temperature applications, it’s worth waiting the full recommended curing time before exposing the joint to stress or movement.

Common Mistakes That Can Undermine Durability

Using an all-purpose sealant where a high-heat product is required is one of the most common missteps. For example, applying a bathroom-grade silicone around a stovetop or engine part could lead to premature failure.

Another issue is neglecting surface prep—if dust or moisture is left behind, even premium products may not adhere properly.

Overapplying product can also lead to inconsistent curing, particularly in hot or humid conditions. This can result in a seal that looks set on the surface but remains soft beneath. In high-heat or variable environments, it’s crucial to use a purpose-designed sealant and follow product-specific instructions to the letter.