Log Burner Installation Cost With No Chimney — Twin-Wall Flue Guide (2026)

The short answer

A complete UK no-chimney install in 2026 — twin-wall flue, mid-range Ecodesign stove, hearth, register plate, CO alarm, and HETAS certification — costs £4,600–£7,300 total. Two-storey houses sit toward the upper end; single-storey homes, shorter flue runs, and external (rather than internal) routes land lower.

The premium over a standard existing-chimney install is £1,800–£3,500, almost entirely driven by the cost of fabricating a flue from scratch using twin-wall insulated stainless steel pipe.

What is a twin-wall flue?

Twin-wall flue is a two-layer insulated stainless steel pipe engineered to safely vent combustion gases when there's no existing masonry chimney. The outer skin stays cool enough to sit close to combustibles; the inner liner can handle 600°C+ continuous flue temperatures.

A complete system comprises straight lengths (typically £90–£120 per metre supply only), 45° or 90° tees, wall support brackets (every 1.8–2m on external runs), a weather collar, storm collar, and an anti-downdraft cowl at the top. For a UK two-storey house you'll need 5–7 metres of flue minimum, often more if the building is tall or the flue must clear a nearby roof ridge.

Itemised no-chimney cost breakdown

Internal vs external flue route — which is cheaper?

Internal route:the flue passes up through ceilings and floors to exit at the roof. Aesthetically tidier but adds boxing, plasterboard, fire-stopping, and often joinery for making good — a typical extra of £500–£1,500 on top of the twin-wall materials. Required where you can't exit externally.

External route:the flue exits at the back of the stove and runs up the outside of a gable wall to clear the roof. Simpler to install, no internal disruption. But brackets every 1.8–2m create a very visible vertical pipe — Reddit r/HousingUK regulars consistently report it's more obvious than marketing photos suggest.

The 2.3m proximity rule

If your no-chimney install is in a garden room, shed, or outbuilding within 2.3 metres of the main house, the flue must terminate at the height of the main house roof — not just the outbuilding roof. That can mean adding 4–6 metres of additional twin-wall pipe at £60–£120 per metre, easily pushing the flue element up by £800–£2,000.

It's a Building Regulations Part J requirement designed to prevent smoke from a low outbuilding flue affecting neighbouring properties. Check the proximity before you commit — it can change the project cost materially.

Building Regulations Part J — what your installer must verify

• Flue height: minimum 4.5 metres above the stove top. Termination ≥600mm above roof ridge if within 600mm of it; otherwise 2,300mm horizontally from any weathered surface and 1,000mm above any intersection.
• Distance to combustibles:a single-skin flue pipe needs clearance of at least 3× its diameter — so a 150mm (6") flue requires ≥450mm clearance to combustibles. Twin-wall has its own (tighter) clearances per manufacturer.
• CO alarm: BS EN 50291-certified, mandatory in the room with the stove. Position high on the wall or on the ceiling, ≥300mm from any wall, between 1m and 3m from the stove.
• Hearth: non-combustible, minimum 840×840mm for freestanding stoves. 12mm thick if stove certified to keep base under 100°C, otherwise 125mm constructional hearth.

What homeowners regret after a no-chimney install

Recurring patterns from r/DIYUK and r/HousingUK threads on no-chimney installs:

• External flue is more visible than marketing photos suggest
• Scaffolding for first-floor exit not included in initial quote (+£300–£800)
• Quote covers materials only, not fire-stopping, hearth, or certification
• Combustible-clearance shortcuts from budget installers — the #1 reason a HETAS inspector deems an install "immediately dangerous"

Recommended stoves for no-chimney installs

Stoves rated 5kW or below don't require an additional permanent air vent in most pre-2008 UK homes — a sweet spot for the no-chimney scenario:

• Charnwood C-Four — £1,195, 5kW, single-lever Quattroflow, 10-year warranty when registered. The most defensible UK-made mid-market pick. Full Charnwood guide →
• Hunter Herald 5 Eco — £1,099, 5kW, optional back-boiler integration, 10-year warranty.
• Stovax Stockton 5— £1,223 (£995 street), triple-air control, the UK's most-installed mid-market wood-burner per Reddit consensus.
• Clearview Pioneer 400 — from £1,500, 5kW, multifuel. UK-made; verify current Ecodesign / clearSkies status with your installer. Clearview context →

Frequently asked questions