CT1 vs Silicone Sealant – Which Should You Use on Site?

When choosing a sealant for construction or trade work, the question often comes up: CT1 or traditional silicone sealant? Both products are widely used on site, but they behave very differently depending on the application.

In this guide, we compare CT1 vs silicone sealant, looking at adhesion, flexibility, durability, and the situations where each product performs best.

What Is CT1 Sealant?

CT1 is a hybrid polymer sealant and adhesive, designed to bond and seal a wide range of materials without the need for primers. It is often used in construction, plumbing, roofing, glazing, and general building work.

Unlike traditional silicone, CT1 acts as both a sealant and a structural adhesive, making it suitable for heavier-duty tasks.

Key Features of CT1

• Bonds to most materials without primer
• Works on wet surfaces or even underwater
• High grab adhesive properties
• Paintable once cured
• Resistant to mould and bacteria
• Excellent vibration and movement resistance

Because of its versatility, CT1 is commonly used for:

• Bonding skirting boards, panels, and trims
• Sealing around baths, showers, and sinks
• Exterior sealing on roofs, gutters, and windows
• Industrial and marine applications

What Is Silicone Sealant?

Silicone sealant is one of the most commonly used sealing products in construction, particularly for bathrooms, kitchens, and glazing.

It is designed primarily as a flexible waterproof sealant rather than an adhesive.

Key Features of Silicone

• Excellent flexibility
• Strong waterproof properties
• Resistant to temperature extremes
• Ideal for expansion joints and glazing

Typical uses include:

• Bathroom sealing around baths and showers
• Kitchen sinks and worktops
• Window glazing
• Sanitary areas where movement occurs

CT1 vs Silicone Sealant: Key Differences

The key difference is that CT1 acts as both an adhesive and a sealant, while silicone is designed purely for sealing.

When Should You Use CT1?

CT1 is typically the better option when you need strong bonding combined with sealing performance.

Tradespeople often choose CT1 when working with:

• Multiple materials (metal, wood, plastic, stone, glass)
• Outdoor installations exposed to weather
• Applications where movement and vibration occur
• Repairs where surfaces may be damp

It is particularly useful on site because it eliminates the need for primers and multiple products, saving time during installation.

When Should You Use Silicone Sealant?

Silicone sealant is still the preferred choice in many sanitary and glazing applications where flexibility and waterproof sealing are the primary requirements.

It works best for:

• Bathroom sealing
• Kitchen worktops
• Window glazing
• Expansion joints

Silicone is usually more cost-effective for straightforward sealing tasks where strong bonding is not required.

Can CT1 Replace Silicone?

In many situations, CT1 can replace silicone, especially where additional bonding strength is useful.

However, silicone still has advantages in certain areas:

• Dedicated sanitary silicone often contains extra mould resistance
• It is cheaper for high-volume sealing work
• Some glazing systems are designed specifically for silicone products

Because of this, many professionals keep both CT1 and silicone in their toolkit depending on the job.

CT1 vs Silicone Sealant: Which Is Better?

There isn’t a single winner – it depends on the task.

Choose CT1 if you need:

• Strong bonding
• A multi-purpose sealant
• Application on damp surfaces
• Exterior durability

Choose silicone sealant if you need:

• A flexible waterproof joint
• A cost-effective sealing solution
• A dedicated sanitary seal

For many tradespeople, the best approach is using CT1 for bonding and structural sealing, while silicone remains ideal for sanitary and glazing work.

✔ Tip: On busy sites, many installers carry CT1 as a general-purpose solution while using silicone only for dedicated sanitary applications.