What Is a FuranFlex Flue Liner?
FuranFlex is a patented chimney lining system that uses a heat-cured composite material. It is installed
into an existing chimney as a flexible resin tube, then expanded and cured using steam to create a
hardened, structurally stable liner. When installed correctly and in accordance with manufacturer
instructions, the result is a smooth, joint-free lining with a consistent internal diameter.
FuranFlex is typically used for:
- Relining existing masonry chimneys that need a new internal flueway.
- Situations where installing rigid sections or traditional liners would be difficult due to bends or access limitations.
- Certain types of gas, oil, or solid-fuel appliances when the manufacturer’s guidance permits it.
The suitability of a FuranFlex liner depends on the appliance type, flue gas temperature, pressure regime
and local regulations. A competent installer should assess each installation individually.
How the FuranFlex System Works
Although the exact method must follow the manufacturer’s current installation manual, a simplified overview is:
- Survey & Measurement
The chimney is inspected for condition, dimensions and straightness. This determines whether
FuranFlex is an appropriate option for the specific appliance and building. - Insertion of the Uncured Liner
A flexible, fabric-like liner impregnated with resin is inserted into the chimney from top or bottom,
depending on the site layout. - Inflation
The liner is expanded with air or steam so that it presses evenly against the inside of the chimney. - Steam Curing
The expanded liner is heat-cured with steam, following the manufacturer’s stated temperature and
pressure controls. Once cured, it becomes rigid and maintains its new shape. - Final Trimming & Connection
Once cooled, the liner is trimmed and connected to the appliance and terminal components using
appropriate fittings.
The finished liner is joint-free and follows the shape of the existing chimney, which can be helpful in
flues that are hard to reline using other methods.
Where FuranFlex Flue Liners Are Commonly Used
FuranFlex liners may be used in a variety of buildings, including:
- Commercial and industrial premises.
- Hotels, restaurants and heritage buildings.
- Large domestic properties with complex chimney layouts.
They are often considered where:
- An existing chimney has an irregular shape or multiple bends.
- Preserving the structure is essential, such as in historic buildings.
- A smooth internal surface is beneficial for future maintenance and draft performance.
Installers must confirm that the selected FuranFlex product variant is compatible with the intended
appliance category and flue gas characteristics.
Benefits of FuranFlex Flue Liners
When used in appropriate applications and installed correctly, FuranFlex liners can provide several benefits:
- Joint-Free Internal Surface
The liner cures as a continuous tube, reducing the number of joints inside the chimney. - Ability to Follow Existing Chimney Shapes
The liner adapts to bends and irregularities, which can be difficult for rigid systems. - Full-Height Relining Without Major Structural Work
No need to dismantle chimney stacks or ceilings in many cases, depending on access. - Smooth Internal Surface
A consistent internal diameter can help with flue performance when correctly sized.
Exact performance characteristics depend on the product variant, chimney condition and appliance type,
so each project must be assessed individually.
FuranFlex vs Traditional Flue Liners
Different lining methods are better suited to different situations. Here is a general comparison:
| System Type | General Characteristics | When It May Be Suitable |
|---|---|---|
| Stainless Steel Flexible Liners | Common for domestic solid fuel or gas appliances where permitted. | Straighter chimneys and standard relining jobs. |
| Rigid Metal Sections | Durable and widely used for commercial chimneys. | Situations with straight or predictable flue routes. |
| FuranFlex (Composite) | Installed soft then steam-cured in place to form a rigid liner. | Complex or difficult-access chimneys (subject to suitability checks). |
The right choice depends on appliance type, chimney condition, installation constraints and regulatory needs.
Regulation & Compliance Considerations
As with all flue systems, FuranFlex installations must comply with:
- Current Building Regulations for the relevant UK nation.
- Applicable British and European Standards for chimneys and flue systems.
- Any manufacturer-specific installation requirements.
- Appliance manufacturer flueing instructions.
Because standards and regulations are updated over time, installers should work to the most current guidance
and ensure all design decisions can be supported by documentation.
Maintenance & Long-Term Care
Maintenance requirements depend on the type of appliance, how it is used and the guidance provided by
the appliance and flue manufacturers. Typical long-term care may include:
- Routine inspection of accessible sections and connections.
- Cleaning or sweeping intervals appropriate to the appliance and fuel used.
- Checking that condensate management and terminations remain clear.
- Monitoring for signs of damage or changes in appliance performance.
Correct maintenance helps prolong the useful life of any flue liner.
Choosing an Installer for FuranFlex Flue Liners
Because FuranFlex requires specialist equipment and trained personnel, it should be installed only by
installers who are experienced with the system and work in accordance with current manufacturer guidance.
When selecting an installer, consider:
- Experience with composite liners and with your appliance type.
- Ability to provide a site survey and confirm suitability of the system.
- Knowledge of relevant regulations and standards.
- Clear method statements and documentation for the curing process.
A professional assessment ensures the liner selected is appropriate for the specific application and
that installation aligns with applicable standards.
FuranFlex flue liners provide a useful option for relining existing chimneys where other methods may be
impractical. Their steam-cured, joint-free construction can be advantageous in chimneys with awkward
shapes or limited access. As with all flue systems, careful assessment, competent installation and
ongoing maintenance are essential to ensure safe and effective operation.
