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Fire Stopping Guide
Intumescent Mastic & Fire-Resistant Sealants Explained
Intumescent mastics and fire-resistant sealants are used within defined passive fire protection systems to protect suitable joints, gaps and service penetrations. Different products have different properties and tested applications, so the terms should not be treated as interchangeable.
Use this guide as a practical introduction, then check the relevant tested system and manufacturer documentation before selecting or installing a product.
Use This Guide
Understand the principle first
Use this guide as a practical introduction, then check the relevant tested system and manufacturer documentation before selecting or installing a product.
Sealants Guide
Quick Guide
Intumescent mastics and fire-resistant sealants are used within defined passive fire protection systems to protect suitable joints, gaps and service penetrations. Different products have different properties and tested applications, so the terms should not be treated as interchangeable.
Key Points
What You Need to Know
Linear Joints
Some sealants are tested for defined wall or floor joints.
Service Gaps
Certain systems cover annular gaps around services.
Batt Systems
Sealants may be used with compatible fire batts.
Movement
Joint movement capability varies by product and system.
Key Principle
What Is Intumescent Mastic?
Intumescent mastic is a sealant formulated to react when exposed to heat. Depending on the product, it may expand to help close gaps around suitable services or form part of a penetration sealing system.
Its permitted applications, movement capability and fire performance depend on the manufacturer evidence.
Practical Guidance
Fire-Resistant Sealants
Fire-resistant sealant is a broad description covering different products designed for defined fire stopping applications. Some are acrylic-based, some contain graphite and others are designed for specific joint or service conditions.
The correct product should be chosen according to the service, substrate, movement and system requirements rather than product name alone.
Selection & Application
Where Are Sealants Used?
Typical applications can include perimeter joints around fire batts, linear joints, small annular gaps and certain service penetrations.
A sealant that is suitable for one application may not be suitable for another, even if both applications require fire resistance.
Important Detail
What to Check Before Selection
Check the substrate, joint width and depth, service type, expected movement, environmental exposure and required fire performance.
Where the sealant forms part of a multi-component system, compatible products should be used in the arrangement covered by the supporting evidence.
Relevant Products
Explore Related Product Ranges
Use the guide to understand the application, then browse the relevant Fire Protection Direct product categories.
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Frequently Asked Questions
Frequently Asked Questions
Intumescent mastic is a specialist sealant that reacts to heat and is used in defined passive fire protection applications.
Not always. Fire-resistant sealant is a broad category and products can use different technologies and have different tested applications.
No. The actual service, substrate, gap and installation arrangement must be within the scope of the product evidence.
A standard sealant should not be assumed to provide the fire performance of a tested fire stopping product.
Required depth varies by product and tested system. The relevant technical documentation should be followed rather than using a generic rule.
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