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Class G chimneys: flues, vent pipes and height limits
Class G can grant planning permission for installing, altering or replacing chimneys, flues and soil and vent pipes on a qualifying house in England.
The height limit is easy to misread. The installation must rise less than 1 metre above the highest part of the roof. Reaching exactly 1 metre above that point is excluded.
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Permitted development can avoid a full planning application, but only if the right applies and every relevant limit and condition is met. Planning Geek can check the planning history, Article 4 directions and other restrictions, and help with a lawful development certificate or prior approval where needed.
The strict height limit
G.1(b) excludes an installation which exceeds the highest part of the roof by 1 metre or more. This is different from a rule allowing “up to 1 metre”.
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| Height above the highest roof point | Result under this test |
|---|---|
| 0.9 m | Within the Class G height limit |
| Exactly 1.0 m | Fails the Class G height limit |
| More than 1.0 m | Fails the Class G height limit |
Use the highest part of the roof, not the lower point where the flue emerges, and do not substitute the top of an existing chimney as the roof datum. Passing this measurement does not establish compliance with every other requirement.
Extra restrictions on protected land
On article 2(3) land, Class G does not permit the installation on a wall or roof slope which:
- Fronts a highway, and
- Forms either the principal elevation or a side elevation of the house
Both elements belong to the test. A highway-facing side wall on a corner plot needs particular care. The rule is not a blanket ban on every chimney anywhere in a conservation area, nor does it turn simply on whether the chimney can be seen from the road.
Article 2(3) land includes conservation areas, National Parks, the Broads, National Landscapes and World Heritage Sites. For Part 1, highway includes an unadopted street or a private way.
Check the house and its planning history
- The right is for a dwellinghouse, not a flat, maisonette or building containing flats
- It is unavailable where permission to use the house as a house arose only through Part 3 Classes G, M, MA, N, P, PA or Q
- A dwellinghouse built under Part 20 is excluded
- A relevant planning condition or Article 4 direction may remove the right
Class G does not contain a separate blanket listed-building exclusion, but listed building consent may be required for work affecting a listed building’s special character. The existing building and use must be lawful.
Which route covers the proposed equipment?
Class G concerns a chimney, flue or soil and vent pipe on a house. It should not be used as a general permission for unrelated external plant or every freestanding structure in a garden. Some domestic energy installations have separate rights under Part 14; check the relevant class and its own conditions.
Other roof works may need Class B or Class C. Neither class incorporates the installation, alteration or replacement of a chimney, flue or soil and vent pipe into its permission.
Planning and safe installation are separate
Class G has no prior approval procedure. If all requirements are met and the right is available, the GPDO grants planning permission. A certificate of lawfulness for proposed development can confirm the position before installation.
Planning compliance does not establish that the height, terminal position or construction meets Building Regulations and the relevant installation requirements. Obtain those checks from an appropriately qualified installer or specialist.
Sources and Class G legislation
Checked against the current GPDO Part 1 and article 2 definitions. The government householder technical guidance provides explanations and examples, but must be read with subsequent amendments to the legislation.
Read the Class G legislation
Class G – chimneys, flues etc on a dwellinghouse
Permitted development
G. The installation, alteration or replacement of a chimney, flue or soil and vent pipe on a dwellinghouse.
Development not permitted
G.1 Development is not permitted by Class G if—
(a)permission to use the dwellinghouse as a dwellinghouse has been granted only by virtue of Class G, M, MA, N, P , PA or Q of Part 3 of this Schedule (changes of use);
(b)the height of the chimney, flue or soil and vent pipe would exceed the highest part of the roof by 1 metre or more;
(c)in the case of a dwellinghouse on article 2(3) land, the chimney, flue or soil and vent pipe would be installed on a wall or roof slope which—
(i)fronts a highway, and
(ii)forms either the principal elevation or a side elevation of the dwellinghouse ; or
(d)the dwellinghouse is built under Part 20 of this Schedule (construction of new dwellinghouses).
Explore GPDO Part 1
Choose the work you are planning. These guides explain the English rules for houses.
- Part 1 overview
Start here for permitted development at a house - Class A: house extension and alteration
Rear and side extensions, windows and doors - Class AA: additional storeys
Build upwards above an existing house - Class B: roof enlargement
Dormers and hip-to-gable enlargements - Class C: other roof alteration
Rooflights and other roof alterations - Class D: porch
Porches outside an external door - Class E: outbuilding
Garden buildings, pools and other incidental development - Class F: hard surface
Driveways, paths and patios - Class G: chimney and flue
Chimneys, flues and soil and vent pipes - Class H: satellite dish
Microwave antennas on the house or in its curtilage - Paragraph I: definitions
Terms used in Part 1
Page Updated: 25th September 2026