Disclaimer: This guide is for general information purposes only. It is not a substitute for professional advice. Always consult a HETAS-registered or other suitably qualified installer before purchasing or fitting a stove and flue system. Building Regulations and manufacturer requirements must be followed.
Why Getting Your Flue Right Matters
A wood-burning stove is only as good as the flue system behind it. Poor flue sizing causes poor draw, smoky rooms, and potential safety hazards. Choosing the right liner, diameter, and height before you buy a stove saves you significant cost and disruption later. This checklist walks you through everything you need to confirm before placing an order.
Pre-Purchase Flue Checklist
Step 1 — Check the Stove Outlet and Required Flue Size
Many stoves have a 125 mm (5-inch) or 150 mm (6-inch) outlet, while some larger models require a bigger flue. Check the installation manual for your exact model.
The connecting flue pipe and chimney liner are different components. Do not assume that a 125 mm stove outlet means a 125 mm liner is suitable. In England, 150 mm is generally the minimum chimney flue diameter for wood-burning stoves; a 125 mm flue may be permitted for an appropriate DEFRA-exempt appliance up to 20 kW, provided the manufacturer's instructions allow it. Ecodesign compliance alone does not establish this exemption. Your installer must confirm the size for your stove, fuel and installation, including the rules in your part of the UK.
Do not reduce the flue below the appliance outlet or the manufacturer's specified minimum. Any increase in diameter and any adaptor must be specified by your installer.
Some stove outlets require a particular connection adaptor. Our Opus/Bronpi European Flue Adaptor is for compatible models and sizes only. Likewise, the Arada 5 Inch Flue Spigot is a model-specific component, not a universal fitting. Confirm compatibility before ordering.
Step 2 — Determine Your Flue Route: Existing Chimney or Twin-Wall System?
You have two main options for routing flue gases from your stove to the outside:
-
Existing masonry chimney — an installer must assess its condition, dimensions and suitability, including whether it needs lining or relining (see Step 3).
- Twin-wall insulated flue system — if there is no existing chimney, a twin-wall system is usually run internally or externally. Its route, diameter, height, supports and clearances must be designed for the property and appliance.
Decide which route applies to your property before moving to the next steps.
Step 3 — Assess Your Liner Requirements
A new flexible liner is not automatically compulsory simply because you are fitting a new stove to an existing chimney. The installer must establish that the chimney is sound, suitably sized and safe for its intended use. Lining or relining may be necessary following that assessment or to meet the appliance manufacturer's requirements.
- Choose a liner approved for the appliance, fuel and operating conditions. Stainless-steel grade alone does not establish suitability; follow the liner manufacturer's specification.
- A flexible liner should be installed in a single length without joints inside the chimney. It normally connects to the stove's connecting flue pipe through a suitable adaptor.
- Any insulation must be suitable for the liner system and installed according to its manufacturer's instructions and the installer's design.
Browse our Installation & Flue Accessories collection for the fittings currently available. Ask your installer to specify the components you need before ordering.
Step 4 — Record the Information Your Installer Needs
Gather the stove manual, room dimensions and any existing chimney information. Photographs of the fireplace and roofline can help with an initial discussion. Leave roof access and internal chimney measurements to a suitable professional.
- Chimney dimensions and condition — these help the installer assess suitability and whether a specified liner will fit.
- Effective flue height — measured vertically from the stove outlet to the discharge point. A height of around 4.5 m is a common starting point in England's guidance, not a guarantee of adequate draught or a universal rule.
- Flue termination position — this depends on roof geometry, openings, adjacent buildings and local conditions. Your installer should check Diagram 17 of England's Approved Document J, or the applicable guidance elsewhere in the UK. Thatched and other readily ignitable roofs need particular consideration.
- Bends and offsets — these affect resistance and cleaning access. Your installer must check the proposed route.
- Room dimensions and building characteristics — these help assess heat demand and ventilation. Room volume alone does not determine stove output or flue size.
Step 5 — Consult a Qualified Installer Before Buying
Arrange an assessment before finalising your stove and flue purchase, even if the chimney has recently been swept. Sweeping alone does not confirm that a chimney is suitable for a new appliance.
In England and Wales, a HETAS-registered installer can normally self-certify eligible work within their registration. Alternatively, the appropriate Building Control approval route is required. Scotland and Northern Ireland have different building standards and notification arrangements; contact the relevant local authority before work begins.
Tell your installer if the building is listed, has a thatched roof, or is in a Smoke Control Area. Ask them to confirm ventilation, carbon monoxide alarm provision, clearances, sweeping access and commissioning requirements as part of the installation.
Find a registered installer and consumer advice at HETAS.
Quick Reference: Measurements to Record
| Measurement | Why It Matters |
|---|---|
| Stove flue outlet diameter | Starting point for checking the specified flue size |
| Chimney internal diameter | Confirms liner will fit |
| Effective flue height (m) | Helps the installer assess draught |
| Terminal position relative to roof, openings and nearby buildings | Helps check applicable termination clearances |
| Number of bends in run | Affects draw calculation |
| Room volume (m³) | Helps size stove kW output |
Flue Accessories from The Bijou Stove Company
Once you have confirmed your specification with an installer, browse our curated range of flue components:
- Opus/Bronpi European Flue Adaptor — for compatible Opus/Bronpi models; confirm the required size
- Arada 5 Inch Flue Spigot — for compatible Arada models only; confirm the exact fit
- Installation & Flue Accessories — full collection
Checked October 2026. This guide does not replace a site assessment or installation instructions. Regulations differ across the UK. Confirm current local requirements and both the appliance and flue manufacturers' instructions with your installer.