Mi Flues

Mi-Flues Chimney & Twin-Wall Flue Systems

Mi-Flues is a specialist chimney and flue manufacturer established in 1988, supplying products for domestic, commercial and industrial heating applications.

Its wider range includes flexible chimney liners, insulated twin-wall chimney systems, single-wall connecting flue, gas venting and specialist chimney components.

Bonfire’s current Mi-Flues manufacturer category is deliberately more focused and contains a TWPro Black adjustable wall support for compatible insulated twin-wall chimney installations.

Because flue components form part of a complete tested chimney system, the most important consideration is not simply whether a bracket looks the correct size. The manufacturer, system family, diameter and required wall distance must all match.

Mi-Flues TWPro

TWPro is Mi-Flues’ insulated twin-wall chimney system for applications where a conventional masonry chimney is unavailable or unsuitable.

Twin-wall chimney is commonly used for:

• Wood-burning stoves
• Multi-fuel appliances
• Selected gas appliances
• Selected oil appliances
• Internal chimney routes
• External chimney systems
• Properties without an existing chimney

The insulated construction helps keep flue gases warmer as they travel through the system while maintaining the required separation between hot combustion gases and the surrounding building.

Mi-Flues TWPro Black Wall Support

The current Mi-Flues product stocked by Bonfire is a black adjustable wall support for the TWPro system.

Its purpose is to stabilise a vertical twin-wall chimney where the system runs alongside a wall.

The support can be adjusted to create approximately 130mm to 210mm stand-off from the wall, allowing the chimney position to be coordinated with roof overhangs, gutters, wall details and the required clearance from the building.

The current Bonfire component is listed for a Ø175mm compatible flue outside diameter. Always confirm the exact TWPro system and diameter before ordering rather than selecting a bracket simply because the nominal stove outlet appears similar.

Wall Supports Provide Lateral Support

This distinction is important.

A standard adjustable wall support is intended primarily to provide lateral stability. It holds the vertical chimney in position against sideways movement.

It is not automatically a load-bearing support designed to carry the complete vertical weight of the chimney.

A full external twin-wall installation can therefore require other components such as:

• Base or wall supports
• Wall bands
• Adjustable wall brackets
• Tees and inspection caps
• Roof supports
• Fire stops
• Flashings
• Storm collars
• Terminal cowls

The structural support strategy should be designed around the complete chimney height and route.

Why Is the Wall Distance Adjustable?

An external chimney cannot always run tight against the wall.

The stand-off may need to accommodate:

• Roof eaves
• Guttering
• Window projections
• Stone or brick detailing
• External insulation
• Combustible clearances
• The route required to reach a safe terminal position

An adjustable support allows the chimney to remain vertically aligned while achieving the required separation from the building.

Do Not Mix Twin-Wall Flue Systems Without Checking

Twin-wall chimney components from different manufacturers can look very similar but should not be assumed to be interchangeable.

Differences can include:

• Internal and external diameters
• Insulation thickness
• Joint design
• Locking bands
• Support dimensions
• Approvals and system designation

If an existing chimney is already installed, identify the manufacturer and exact product family before ordering replacement brackets or extensions.

A Mi-Flues TWPro component should therefore be matched to the compatible TWPro system unless the manufacturer specifically confirms otherwise.

Twin-Wall Flue or Flexible Chimney Liner?

These solve different problems.

A flexible chimney liner is normally installed inside an existing suitable masonry chimney.

An insulated twin-wall chimney creates a new chimney route where no usable masonry chimney exists or where the installation design requires a new system.

A stove installation can also use single-wall stove pipe between the appliance and the point where the insulated chimney begins.

The transition between these components must be made using the correct approved adaptors.

Planning a Twin-Wall Chimney

A chimney system should be designed as a complete route rather than assembled one component at a time.

Before ordering, establish:

• Appliance flue-outlet size
• Required chimney diameter
• Internal or external route
• Total chimney height
• Wall stand-off
• Bends or offsets required
• Support locations
• Distances from combustible materials
• Roof or wall penetration
• Required terminal position

The final chimney height and termination also need to provide suitable draught and comply with the relevant installation requirements.

Mi-Flues Supply & Installation from Bonfire

Bonfire has extensive in-house experience designing and installing chimney and flue systems for wood-burning, gas and other heating appliances.

Our design and installation service can include site surveys, chimney calculations, twin-wall specification, structural supports, roof penetrations, flashings, commissioning and testing.

For supply-only orders, the final system design and component suitability should be confirmed by the competent person responsible for the installation.

Mi-Flues FAQs

What does Mi-Flues manufacture?

Mi-Flues manufactures chimney and flue products including flexible liners, insulated twin-wall chimney, single-wall flue and specialist commercial and domestic chimney components.

What is Mi-Flues TWPro?

TWPro is an insulated twin-wall chimney system used for suitable solid-fuel, gas and oil appliance installations where a manufactured chimney system is required.

What does a twin-wall wall support do?

A wall support stabilises a vertical chimney against lateral movement and maintains its position away from the building. Standard wall supports should not automatically be treated as load-bearing chimney supports.

How adjustable is the Mi-Flues wall support sold by Bonfire?

The current TWPro Black wall support stocked by Bonfire provides approximately 130–210mm adjustment from the wall.

Can I use a Mi-Flues bracket on another brand of twin-wall chimney?

Do not assume so. Twin-wall systems can differ in diameter, joint design and approval. Match components to the exact chimney system unless compatibility has been specifically confirmed.

Can Bonfire design my complete twin-wall chimney?

Yes. Bonfire can survey suitable properties and specify the flue diameter, route, supports, clearances, flashings and terminal as part of a complete stove and chimney installation.