FAQs

Fire mastic, also known as fire-rated mastic or intumescent sealant, is used to seal gaps, joints and linear seals where fire resistance needs to be maintained. Common applications include construction joints in walls, perimeter gaps around fire-resistant building elements, and service penetrations where pipes, cables or other services pass through fire-rated walls and floors. Fire-stopping mastics help restrict the spread of fire, smoke and hot gases through these openings. Always use a tested and certified fire-stopping system that is suitable for the specific application and construction type, and refer to the relevant certification and installation guidance before use.

Yes, once fully cured or dry, most fire-rated mastics and intumescent sealants can be painted over. Painting can help achieve a neat finish while maintaining the appearance of fire-stopping and fire-sealing installations. However, compatibility may vary between products, so always refer to the relevant product datasheet, technical data sheet or manufacturer’s guidance for specific painting recommendations and application instructions.

Some fire-rated mastics and intumescent sealants may offer water resistance once fully cured; however, performance can vary depending on the product and application. It is always recommended to consult the relevant product datasheet or technical data sheet to confirm suitability for the intended environment. Where high levels of moisture are expected, or for external fire-stopping applications, a silicone-based fire-rated sealant is generally the recommended solution due to its suitability for exposed and damp conditions.

The curing time for fire-rated mastic and intumescent sealant can vary depending on the product type, application depth and site conditions. In most cases, fire mastic will cure within 24 to 48 hours. Factors such as temperature, humidity and ventilation may affect drying and curing times. For product-specific guidance, always refer to the relevant technical datasheet or manufacturer’s installation instructions.

Fire mastic, also known as fire-rated mastic or intumescent sealant, is used to seal gaps, joints and linear seals in walls and other building elements to help prevent the passage of fire, smoke and hot gases. Fire-stopping mastics are commonly used around construction joints, service penetrations and perimeter gaps where fire resistance needs to be maintained. To ensure compliance and performance, always check the relevant certification, technical documentation, and fire test evidence, and use a tested fire-stopping solution that is suitable for the specific application and construction type.

Selecting the correct fire-rated sealants for a fire door installation is essential to maintaining the fire performance of the door assembly and helping to prevent the spread of fire and smoke.

When sealing gaps between the fire door frame and the surrounding wall, it is important to use products that have been tested in fire door assemblies and comply with the recommendations of BS 8214:2016.

When choosing a fire-rated sealant, check that:

• Fire-rated mastics have been successfully tested as a linear gap seal in accordance with BS 476-20 or BS EN 1366-4 for the required fire resistance period.
• Fire-rated expanding foams have been successfully tested as a linear gap seal in accordance with BS 476-20 or BS EN 1366-4 and provide a minimum of 30 minutes fire resistance.
• The sealant has been included within a fire test between the door frame and surrounding structure on a timber-based fire door assembly tested in accordance with BS 476-22 or BS EN 1634-1.

If a product does not provide this information, you should request the relevant fire test evidence and certification before specifying or installing it.

FAS Fire Door Foam™ and FAS Fire-Rated Acrylic Sealant have been independently tested for use in fire door assemblies and are Certifire approved under certificates CF5839 and CF5840. When used individually, both products can provide up to 60 minutes of fire protection. When used together as a tested system, they can achieve up to 120 minutes of fire resistance.

Typical applications include:

• FAS Fire Door Foam™ for gaps up to 25mm to achieve up to 60 minutes of fire protection.
• FAS Fire-Rated Acrylic Sealant for gaps below 5mm to achieve up to 60 minutes of fire protection.
• A minimum 10mm cap of FAS Fire-Rated Acrylic Sealant over FAS Fire Door Foam™ to achieve up to 90–120 minutes of fire protection.
• Installation with standard packers as part of the tested system.

FAS Fire Door Foam™ also replaces the need for mineral fibre wool, helping to reduce installation time by approximately 12 minutes per doorset installation.

For further technical advice on selecting the correct fire door sealants, please contact our team on 0121 521 2179 or [email protected].

Yes, FAS Fire Door Intumescent Acrylic Sealant can be used in applications where smoke control is required. The sealant has smoke leakage test evidence in accordance with BS EN 1634-3: 2004, demonstrating its suitability for use as part of a tested fire and smoke sealing system. In addition to providing fire resistance, the sealant helps maintain the integrity of compartmentation by restricting the passage of smoke through joints and perimeter gaps. Always refer to the relevant certification, test evidence and installation guidance to ensure suitability for your specific application.

FAS Fire Door Foam™ is a fire-rated expanding foam designed to simplify fire door installation and fire-stopping applications. Compared to traditional stone mineral fibre wool, it offers a quicker and more cost-effective installation method, helping to reduce labour time and overall project costs. When used with FAS Fire Door Intumescent Acrylic Sealant, it forms part of a tested fire door sealing system for perimeter gap sealing around fire door frames.

FAS Fire Door Silicone Sealant has been fire tested to provide up to 60 minutes of fire resistance when used in timber fire doors and timber glazed screens. The sealant has been tested in accordance with BS 476: Part 22: 1987 and BS EN 1634-1, demonstrating its suitability for use as part of a tested fire door sealing system. Always refer to the relevant certification, fire test evidence and installation guidance to ensure the product is suitable for your specific fire door or glazing application.

All relevant information can be downloaded on this website