Silicone & Sealants

What is a Sealant?

A sealant is a material used to block the passage of fluids, air, or other substances through openings or joints in materials. While some are rigid, most are engineered to be flexible, allowing them to accommodate movement between different building components without cracking or losing adhesion.

The primary functions of a sealant are to:

• Waterproof: Prevent water ingress in areas like bathrooms, kitchens, and exterior joints.
• Weatherproof: Protect against rain, wind, and UV radiation in outdoor applications.
• Provide Flexibility: Accommodate natural expansion and contraction of building materials.
• Fill Gaps: Create a clean, aesthetic finish over gaps and cracks.
• Provide Specialist Protection: Offer specific properties such as fire resistance or mould prevention.

In the UK and Europe, sealants are classified by the BS EN 15651 standard, which certifies their suitability for different applications, such as for facades (exterior walls), sanitary joints, or glazing.

Types of Sealants

While there are many specialist formulations, most sealants can be grouped into several key categories based on their intended application.

General Purpose Sealants

These are the versatile, everyday products designed for simple interior filling and sealing tasks where high flexibility or extreme weather resistance is not a priority. 

Often based on acrylic polymers, they are easy to apply and can be painted over, making them ideal for sealing gaps around skirting boards, architraves, and window frames before decorating.

• Primary Use: Interior gap-filling and decorating.
• Key Properties: Paintable, low odour, easy to tool.

Shower & Bath Sealants (Sanitary Sealants)

This is a specialist category of sealant, almost always silicone-based, designed for high-humidity environments. Its critical feature is the inclusion of a powerful fungicide, which actively resists the growth of mould, mildew, and bacteria. 

These "sanitary" grade sealants provide the necessary flexibility to accommodate movement, preventing cracks and leaks. They typically use an acetoxy cure system, which releases a characteristic vinegar-like smell as it cures.

• Primary Use: Sealing around baths, shower trays, sinks, and kitchen worktops.
• Key Properties: 100% waterproof, excellent mould resistance, durable finish.

Building & Roofing Sealants

Designed for demanding exterior applications, these sealants offer superior performance characteristics. They are engineered for high movement accommodation, allowing them to expand and contract with temperature changes without failing. 

They also have excellent adhesion to a wide range of construction materials and high resistance to UV radiation and weathering. These are often based on "neutral cure" silicone or other advanced polymers, which have a lower odour and offer better adhesion to metals and plastics.

• Primary Use: Sealing exterior window and door frames, expansion joints, guttering, and roofing components.
• Key Properties: High flexibility, excellent weather and UV resistance, strong adhesion.

Intumescent Sealants (Fire Stopping)

Intumescent sealant is a specialist product used as part of a building's passive fire protection system. In the event of a fire, the sealant is designed to swell or expand dramatically when it reaches a certain temperature. 

This expansion seals gaps and joints in walls and floors, preventing the passage of fire and smoke from one compartment to another for a specified period (e.g., up to 4 hours). It is a critical component for sealing around pipes, cables, and construction joints in fire-rated walls.

• Primary Use: Fire stopping gaps and linear joints in fire-rated structures.
• Key Properties: Expands in heat to block fire and smoke, provides acoustic insulation.

Considerations for Application

• Preparation is Everything: The single most important factor for a successful seal is a clean, dry, and dust-free surface. Use cleaning spirits or alcohol wipes to remove any soap scum, grease, or old sealant residue before you begin.
• Use a Primer (If Required): For difficult surfaces like some plastics or porous stone, a specialist primer may be needed to ensure proper adhesion.
• Tooling for a Professional Finish: Immediately after applying the sealant, smooth the bead using a sealant finishing tool or a wet finger dipped in a mild soap solution. This creates a neat, compressed seal that adheres correctly to both surfaces.
• Observe Curing Times: All sealants need time to "cure" and develop their final properties. Do not expose a newly sealed area to water until it has fully cured, as per the manufacturer's instructions.