Class G flues in a smoke control area

A flue for a wood burning stove is usually permitted development on a house, and the limit that matters is height: under Class G of Part 1 of Schedule 2 to the General Permitted Development Order 2015, a chimney, flue or soil and vent pipe must not exceed the highest part of the roof by 1 metre or more. Fit a flue that stands a metre or more above the ridge and you have lost the permitted development right for the whole installation rather than for the top section alone.

Permitted development is only half the question. In a smoke control area the appliance and the fuel are controlled separately under clean air legislation, enforced by the council, and a flue that is lawful in planning terms can still leave you with an appliance you cannot lawfully use. Those two systems do not talk to each other.

The height and position limits on a flue

Class G covers the installation, alteration or replacement of a chimney, flue or soil and vent pipe on a dwellinghouse. The height limit is expressed against the highest part of the roof, which on a house with a ridge and a lower rear outrigger means the ridge.

Measure it properly. The highest part of the roof includes any existing chimney stack where the stack is part of the roof structure, and a flue fitted to a rear elevation still measures against the highest part of the roof rather than against the roof slope it emerges from. On a sloping site, the measurement is a vertical dimension between the flue top and the roof, so site levels do not come into it in the way they do for extensions.

Nothing in Class G permits a flue on a building that is not a dwellinghouse. Flats, maisonettes and converted buildings in other uses are outside the class, which is why a flue on a block of flats usually needs an application.

The front elevation restriction on article 2(3) land

On article 2(3) land, which means conservation areas, National Parks, National Landscapes, World Heritage Sites and the Broads, Class G does not permit a flue installed on a wall or roof slope which fronts a highway and forms either the principal elevation or a side elevation of the dwellinghouse.

Three words do the work there.

So in a conservation area a flue on the rear roof slope is usually fine, and the same flue on the front slope of the same house needs planning permission. Where the house is on a corner plot, both the front and the flank may be caught.

The restriction is about visibility from the street, and officers assess an application for a front flue on exactly that basis. A slim matt black twin wall flue on a slate roof is a different proposition from a stainless steel one, and saying so in the application helps.

Smoke control areas and exempt appliances

Most urban England is covered by smoke control areas. Inside one, you may only burn authorised fuels unless the appliance is an exempt appliance approved for burning a specified fuel. In England the rules on emitting smoke in a smoke control area are enforced by the local authority through financial penalties following changes made by the Environment Act 2021, and the sale of the most polluting domestic solid fuels has been restricted since 2021.

What that means for a householder:

• Check whether the address is in a smoke control area with the council before buying a stove
• If it is, choose an appliance on the published list of exempt appliances, and note the fuel it is approved for
• Burn only the fuel the exemption covers, or an authorised fuel
• Keep the appliance documentation, because that is what you produce if a complaint is made

An appliance that is exempt is not exempt for every fuel. Several are approved for wood only, and burning smokeless coal in them takes you outside the exemption.

Flues on a listed building

Class G does not displace the need for listed building consent. Installing a flue on a listed building affects its character as a building of special architectural or historic interest, so consent is needed whether or not the work is permitted development in planning terms.

The internal works matter as much as the external flue. Opening up a blocked fireplace, cutting through a historic ceiling or chimney breast, and lining a historic stack are all works affecting the building, and a scheme that only shows the flue outside will be queried.

Expect conservation officers to resist new external flues on principal elevations and to prefer reuse of an existing stack. Where an existing stack can be lined, that is nearly always the route of least resistance.

Conservation area and the principal elevation

Identifying the principal elevation is the single most common point of argument on these applications. The front door is the usual indicator, but not always: a Victorian villa turned to face a later road, a farmhouse with a formal front facing a garden, and a converted barn with no obvious front all cause trouble.

Look at the architecture rather than the address. The elevation with the architectural hierarchy, the better detailing and the original principal entrance is usually the principal elevation, and the government's technical guidance for householders sets out the approach.

Where it is still unclear, apply for a lawful development certificate for proposed development rather than building and hoping. A certificate under section 192 of the Town and Country Planning Act 1990 is the only formal way to confirm that works are lawful, and it costs far less than relocating a flue after a complaint. The same logic applies to other Part 1 limits, as the note on front garden paving, permeable surfaces and Class F explains for surfacing works.

Neighbour amenity and plume dispersal

Where an application is needed, the planning issues are appearance and smoke. A flue terminating below the level of a neighbour's upper window, or close to it, puts combustion products where somebody opens a window, and that is a legitimate amenity objection.

Practical answers: terminate the flue above the ridge line where the height limit allows, keep it at least the distances recommended in the combustion appliance guidance from openings and boundaries, and locate it away from neighbouring windows rather than at the nearest convenient point to the stove.

Illustrative example. A terraced house in a conservation area, stove installed against a party wall, flue proposed on the rear slope 400 millimetres from the boundary and terminating 600 millimetres below the neighbour's bedroom window. Moving the stove to the chimney breast and lining the existing stack removed both the planning issue and the amenity objection, at a lower cost than the external flue. Figures are illustrative.

Building Regulations running alongside

Approved Document J governs the installation: hearth construction, flue size and material, clearances to combustibles, air supply for combustion, flue outlet positions, and a carbon monoxide alarm. Compliance is confirmed either through building control or by a registered competent person scheme installer.

Three points householders miss. A flue that satisfies Class G can still fail the outlet position requirements in the guidance, because the two sets of rules measure different things. Air supply for a stove above a stated output needs a permanent vent, which affects the room. And the installation certificate is what a buyer's solicitor asks for, so keep it.

Where any of this has to be explained to a case officer, a short Planning Statement describing the appliance, the flue specification, the termination height and the distances to neighbouring openings answers the questions before they are asked. For other Part 1 limits that catch householders, the note on the 50 per cent curtilage rule for garden outbuildings is a useful comparison.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.