Class G and Class H: flues, chimneys, antennas and dishes

Flue and antenna permitted development for a house sits in two short classes of the General Permitted Development Order, and both have limits people trip over. Class G of Part 1, Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015 allows the installation, alteration or replacement of a chimney, flue or soil and vent pipe on a dwellinghouse, provided it does not project a metre or more above the highest part of the roof. Class H allows antennas, including satellite dishes, on a house or in its curtilage, subject to limits on number, size and position. Neither class applies to a flat.

Both classes are also removed or restricted on designated land, and neither one touches listed building consent.

What Class G covers

Class G is the permission you rely on for a new boiler flue through a wall, a soil and vent pipe serving a new bathroom, a rebuilt chimney stack, or a flue for a wood burning stove. It was widened some years ago so that flues serving biomass and combined heat and power systems on a house fall within it as well, which is why you do not need a separate microgeneration class for a wood pellet boiler flue.

What it does not cover is a flue on a flat, a flue on a building that is not a dwellinghouse, or any structure that goes beyond a chimney, flue or vent pipe. A flue enclosed in a new projecting masonry casing starts to look like an extension and is assessed as one.

The class covers installation, alteration and replacement equally, so swapping a stainless flue for a larger one is development that has to meet the same limits afresh.

The one metre height limit

The single numerical limit in Class G is that the chimney, flue or soil and vent pipe must not exceed the highest part of the roof by one metre or more. Measure from the highest point of the roof, not from the ridge nearest the flue, and not from the eaves.

Two things follow. On a house with a dominant main ridge and a lower rear outrigger, a flue on the outrigger has a generous allowance because the comparison is with the highest part of the whole roof. And on a bungalow with a shallow roof, a flue that needs height for draught can run out of allowance quickly.

Building regulations are the other constraint and they often bite first. Approved Document J sets out where a flue outlet may sit relative to the roof surface, ridges, adjacent openings and boundaries, and those requirements are independent of planning. A flue can comply with Class G and fail Part J, or the reverse. Design to both.

Front elevations and designated land

On article 2(3) land, which means a conservation area, a National Landscape, a National Park, the Broads or a World Heritage Site, Class G does not permit a chimney, flue or vent pipe on a wall or roof slope that fronts a highway and forms either the principal elevation or a side elevation of the house.

Read that carefully, because two conditions have to be met together. The wall or roof slope has to front a highway, and it has to be the principal or a side elevation. A flue on a rear roof slope in a conservation area is normally still permitted development, even where the rear is visible from a footpath, because the rear is neither elevation type. A flue on the front of the same house needs an application.

Whether something fronts a highway is a question of fact about the relationship between the elevation and the road, and a highway includes a public footpath or bridleway. Where a corner plot has two road frontages, both the principal elevation and the side elevation are caught.

Where rights have been removed altogether, whether by an Article 4 direction or by a condition on the original permission, none of this helps. Our note on using section 73 to remove a permitted development condition covers the route where a condition is the obstacle.

What Class H covers for antennas

Class H covers the installation, alteration or replacement of an antenna on a house or within its curtilage, which includes television aerials, satellite dishes and, in principle, other receiving and transmitting equipment for domestic use.

The class has several interacting limits and they are easier to check in the Order than to summarise. The ones that catch householders are these. No more than two antennas are permitted on the house and its curtilage taken together, so a dish plus an aerial uses the whole allowance and a third piece of equipment needs an application. Antennas are not permitted on a chimney, wall or roof slope facing onto and visible from a highway where the house is on article 2(3) land. And there are height restrictions tied to the roof and the chimney, so an antenna on a roof without a chimney must not stand higher than the highest part of the roof.

Buildings over 15 metres in height are treated differently, which rarely matters for a house and matters a great deal for a block of flats, where Part 1 does not apply in the first place.

Size and number limits for dishes

The size limits are expressed as the largest linear dimension of the antenna, excluding any projecting feed element, reflector, mast or brackets. For a house the limit is one metre, and an antenna mounted on a chimney is held to a much smaller dimension of 60 centimetres.

A domestic satellite dish is typically well inside the one metre figure, so the limits that actually bite are the number, the chimney dimension and the height restrictions. Larger dishes for broadband or specialist reception are where the size limit becomes real.

Before you rely on any of this, check the current text of Part 1 Class H on legislation.gov.uk and read the government's technical guidance for householders alongside it. The class has been amended more than once, and secondary sources repeat old figures.

Siting to reduce visual effect

Class H carries two conditions that are easy to overlook and are enforceable in their own right. The antenna must be sited so far as practicable to minimise its effect on the external appearance of the building, and it must be removed as soon as reasonably practicable once it is no longer needed for reception or transmission.

The siting condition is a genuine obligation rather than advice. Where a rear-facing position would give adequate reception and the installer has put the dish on the front for convenience, the council can take the view that the condition is breached and that the installation is therefore not permitted development at all.

The practical answer is to record the decision. A note of the reception test at the alternative positions, with the date and the installer's name, is short and it answers the question if it is ever asked.

Listed buildings, flats and Article 4 directions

Permitted development rights do not remove the need for listed building consent. A flue or a dish on a listed building, or fixed to a curtilage structure that forms part of the listing, needs consent, and unauthorised work to a listed building is a criminal offence with no time limit on enforcement. Pair any application with a Heritage Statement that addresses the effect on significance.

Flats have no Part 1 rights at all. Neither Class G nor Class H is available to a flat owner, which means a new boiler flue through the wall of a converted flat is development requiring planning permission unless it falls within some other class. This is one of the most frequently missed points in householder work.

Article 4 directions in conservation areas commonly remove Part 1 rights in whole or in part, and the terms of each direction differ. Check the council's published list of directions rather than assuming the standard householder rights apply. Where the curtilage itself is uncertain, our note on measuring curtilage and the enlarged garden explains how the boundary is judged.

Smoke control areas and biomass flues

A flue that complies with Class G tells you nothing about what you may burn. In a smoke control area declared under the Clean Air Act 1993, it is an offence to emit smoke from a chimney unless you are using an authorised fuel or an exempt appliance, and the lists of both are maintained by Defra.

So a wood burning stove installed under Class G in a smoke control area needs to be an exempt appliance, or the owner needs to burn only authorised fuels. Councils enforce this through environmental health rather than planning, and the penalties are separate from anything planning can do.

Check the smoke control position with the council's environmental health team before buying the appliance. Retro-fitting an exempt appliance after installation costs more than choosing the right one.

Permitted development rights are a rule of thumb rather than a guarantee, and an application for a certificate of lawful development under section 192 or section 191 of the Town and Country Planning Act 1990 is the only formal way to confirm that works are lawful. Where an existing right matters to a wider scheme, our note on permitted development as a fall-back material consideration explains how that argument is run, and a Planning Statement is the document that carries it.

This is general guidance rather than legal advice, so 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.