Choosing the correct materials for commercial fire protection is essential. Even relatively small gaps and openings can compromise fire-resistant walls, floors and ceilings, allowing fire, smoke and hot gases to spread between different areas of a building.
Intumescent sealant for commercial buildings helps protect these openings as part of a correctly specified passive fire protection system. When exposed to high temperatures, the sealant expands and forms an insulating char that helps restrict the passage of fire and smoke.
However, not every fire-rated sealant is suitable for every application. The required product will depend on the type of construction, the service passing through the opening, the required fire resistance and the details of the tested fire-stopping system.
This guide explains how intumescent sealants work, where they are used and what should be considered when selecting and installing them in commercial premises.
What Is Intumescent Sealant?
Intumescent sealant is a fire-stopping material designed to expand when exposed to heat. As the temperature rises, the material increases in volume and produces a dense, insulating char.
This reaction helps close gaps and openings that could otherwise provide a route for fire and smoke. Depending on the product and its intended application, the sealant may be used around pipes, cables, conduits, ducts or construction joints.
Intumescent sealants form part of passive fire protection. Unlike active systems such as sprinklers and fire alarms, passive fire protection is built into the structure of a building. Its purpose is to support fire compartmentation and help contain a fire within a defined area for a specified period.
Why Intumescent Sealant Is Important in Commercial Buildings
Commercial buildings often contain large numbers of mechanical, electrical and plumbing services. Every pipe, cable, duct or conduit that passes through a fire-resistant wall or floor creates a penetration that may weaken the compartment line.
If these openings are not correctly protected, they can allow:
- Fire to spread into adjoining rooms or floors
- Smoke and hot gases to pass through compartment boundaries
- Escape routes to become unsafe more quickly
- Fire-resistant construction to perform below its intended rating
- Damage to spread to critical equipment and business assets
Correctly specified fire-stopping systems help preserve compartmentation, protect escape routes and provide occupants with more time to leave the building safely. They can also support the work of the fire and rescue services by slowing the spread of fire and smoke.
This is particularly important in offices, schools, hospitals, care facilities, hotels, warehouses, shopping centres and other premises where there may be complex services or large numbers of occupants.
Where Is Intumescent Sealant Used?
Intumescent sealant can be used in a range of fire-stopping applications, subject to the product’s tested field of application. Common uses include sealing around:
- Electrical cables and cable bundles
- Metal pipes and conduits
- Plastic pipes used with compatible fire collars or wraps
- Service penetrations through fire-resistant walls and floors
- Fire-rated construction joints
- Gaps around suitable door frames and other fire-resistant elements
- Openings containing a combination of approved services
The suitability of a product must always be confirmed against its technical documentation. A sealant tested around a metal pipe, for example, should not automatically be assumed to provide the same performance around a plastic pipe or cable bundle.
How to Choose the Right Intumescent Sealant
Choosing a firestop sealant is not simply a matter of finding a product with the required number of fire-resistance minutes. The complete installation must match a tested or assessed system.
1. Confirm the Required Fire Resistance
Establish the required integrity and, where applicable, insulation performance of the wall, floor or joint. This information should be identified in the building’s fire strategy, project specification or approved fire-stopping schedule.
The selected system must provide the required performance for the specific construction and application. A product described as fire-rated for a particular period may not achieve that rating in every wall, floor or penetration arrangement.
2. Identify the Substrate
Confirm the material through which the service passes. This could include:
- Plasterboard partition systems
- Masonry walls
- Concrete walls or floors
- Composite or specialist fire-resistant constructions
The substrate type and thickness can affect the performance of the fire-stopping system. Only use the product in constructions covered by the relevant test evidence, classification or technical assessment.
3. Check the Penetrating Service
Different services behave differently during a fire. Metal pipes conduct heat, combustible pipes may soften or melt, and cable bundles can leave irregular gaps.
Before choosing a sealant, identify:
- The material of the pipe, cable or duct
- The external diameter or overall dimensions
- Any pipe insulation and its composition
- The number and arrangement of cables
- Whether services are mixed within the same opening
Combustible pipes will often require an additional intumescent device, such as a fire collar or fire wrap. Sealant should not be used as a substitute unless the complete arrangement is specifically supported by appropriate evidence.
4. Measure the Opening
The size and shape of the opening will influence the permitted annular gap, backing material and required sealant depth. If the opening falls outside the tested limits, simply applying more sealant does not make the installation compliant.
Oversized, irregular or complex openings may require a different fire-stopping solution, such as coated fire batt, fire compound or a proprietary penetration seal system.
5. Consider Joint Movement
Some construction joints are designed to accommodate movement. These applications require a fire-rated joint seal with suitable movement capability as well as the necessary fire performance.
Check whether the product is suitable for static penetrations, linear joints or movement joints. A rigid sealant used in a moving joint may crack or separate from the substrate, reducing its effectiveness.
6. Review Environmental Conditions
Consider the conditions the cured seal will experience. Relevant factors may include:
- Internal or external exposure
- Humidity and contact with water
- Operating temperature
- Exposure to chemicals or cleaning products
- Compatibility with adjacent materials
- Whether the sealant needs to be painted
Check the manufacturer’s technical data before using the product in damp, exposed or specialist environments.
7. Verify the Supporting Evidence
Always review the current technical documentation for the complete fire-stopping system. This may include test reports, classification documents, technical assessments, installation instructions and third-party certification.
The documentation should cover the actual substrate, penetration type, opening dimensions, backing material, sealant depth and required fire performance.
How to Install Intumescent Sealant
Installation details vary between products and systems. The manufacturer’s instructions and the approved system detail must therefore take priority. A typical installation may involve the following stages.
1. Inspect the Opening
Confirm that the substrate, service type and opening dimensions correspond with the specified fire-stopping system. Check for damage, unsupported services or other conditions that could affect the installation.
2. Prepare the Surfaces
Remove dust, oil, grease, loose material and other contamination from the surfaces. The substrate should be sound and suitable for adhesion. Any primers required by the manufacturer should be applied as directed.
3. Install the Specified Backing Material
Some systems require mineral wool, backing rod or another approved material behind the sealant. This controls the depth and profile of the seal and can form an essential part of the system’s fire performance.
Use the correct material, density, orientation and compression. Do not substitute an alternative backing product without suitable supporting evidence.
4. Apply the Correct Sealant Depth
Apply the sealant continuously to the depth and width specified in the approved detail. Avoid gaps, voids and air pockets, particularly around cables and irregular penetrations.
Applying too little material may prevent the system from achieving its intended performance. Applying excessive material is not a reliable way to compensate for an incorrect opening or unsuitable system.
5. Tool the Surface
Tool the sealant within the manufacturer’s stated working time. This helps create good contact with the surrounding surfaces and provides a consistent finish.
6. Allow the Sealant to Cure
Protect the installation from water, damage and excessive movement while it cures. Drying and curing times will vary depending on the product, application depth, temperature and humidity.
7. Label and Record the Installation
Where required by the project, attach a fire-stopping identification label and record the installation. Useful records may include:
- The location of the seal
- The product and system reference
- The date of installation
- The installer’s details
- Photographs taken before and after installation
- The corresponding inspection or approval record
Accurate records make future inspection, maintenance and alteration considerably easier.
Common Intumescent Sealant Installation Mistakes
Fire-stopping defects are often caused by small departures from the approved system. Common mistakes include:
- Using ordinary decorators’ caulk instead of a suitable fire-rated product
- Selecting a sealant based only on its headline fire rating
- Using the wrong backing material or installing it incorrectly
- Applying insufficient sealant depth
- Sealing an opening larger than the permitted dimensions
- Using a product around an unapproved service or substrate
- Failing to account for pipe insulation
- Using a static sealant in a movement joint
- Leaving hidden gaps between closely grouped services
- Mixing components from different systems without supporting evidence
- Failing to label, inspect or record completed work
These issues may not be obvious once the installation has been covered or decorated. Fire-stopping work should therefore be checked before it becomes inaccessible.
Maintaining Fire-Stopping in Existing Buildings
Fire-stopping is not only a consideration during new construction. Refurbishment, maintenance and the installation of new building services can disturb existing compartment lines.
New cables are sometimes passed through existing seals, while old services may be removed without the remaining opening being repaired. Any alteration can invalidate the original system if it is not completed in accordance with an approved detail.
Building owners and facilities teams should include fire-stopping within regular fire safety inspections. Damaged, incomplete or undocumented seals should be assessed by a competent person and repaired using a suitable system.
Frequently Asked Questions
Is all fire-rated sealant intumescent?
No. Fire-rated sealants use different technologies and may be intended for different applications. Some products are intumescent, while others rely on alternative formulations. Check the product documentation rather than assuming every fire-rated sealant expands significantly.
Can intumescent sealant be used around plastic pipes?
It depends on the tested system. Plastic pipes often require a compatible fire collar, wrap or other closure device because the pipe can soften and leave a large opening during a fire. Use only an arrangement covered by suitable test or assessment evidence.
Can ordinary sealant be used in a fire-resistant wall?
Ordinary sealant should not be used to protect service penetrations or joints where fire resistance is required. It may burn, shrink or lose adhesion during a fire, leaving an open route for fire and smoke.
How much does intumescent sealant expand?
The expansion ratio varies considerably between products. A larger expansion figure does not automatically mean better performance. What matters is whether the complete system has been tested or assessed for the intended construction, service and opening.
Can I paint over intumescent sealant?
Some products can be overpainted, but paint compatibility and curing requirements vary. Refer to the manufacturer’s technical data and test a small area where appearance is important.
Who should install fire-stopping products?
Fire-stopping should be specified, installed and inspected by people with suitable knowledge and competence. Installers must understand the approved system detail and follow the product manufacturer’s instructions.
Choosing Intumescent Sealant for a Safer Commercial Building
Intumescent sealant plays an important role in protecting penetrations and joints within commercial buildings. When correctly specified and installed, it helps maintain fire compartmentation and restrict the spread of fire and smoke.
The key is to consider the complete fire-stopping system rather than the sealant in isolation. Before installation, confirm the substrate, service type, opening dimensions, backing material, sealant depth, movement requirements and supporting evidence.
Never replace a specified product or alter an approved detail without appropriate technical confirmation. Careful product selection, competent installation and thorough record-keeping will help create a safer and more resilient building.
Written by
Fire Protection Direct Team
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