Boiler Flues in Conservation Areas: Do You Need Permission?

Replacing a boiler in Hampstead often raises a question homeowners elsewhere never have to ask: can the flue go where it needs to go? Most of NW3 and the neighbourhoods around it are conservation areas, and that changes the rules for anything new on the outside of a house. This guide sets out what the national rules say, in plain English, and how they apply here.

Worth knowing: The rules only bite when something changes on the outside. Repairing a boiler, or replacing one where the flue stays in the same place, rarely needs permission at all.

The national rule: permitted development, Class G

In England, many small changes to a house are allowed without a planning application. These are called permitted development rights. Class G of the General Permitted Development Order covers installing, altering or replacing a chimney, flue or soil and vent pipe on a house.

Two limits matter most:

1. Height. A flue or pipe must not rise a metre or more above the highest part of the roof.
2. Conservation areas. On protected land, which includes conservation areas, a flue or pipe is not permitted development if it is on a wall or roof slope that fronts a highway and forms the principal elevation or a side elevation of the house. Both conditions apply together.

In practice, that means a flue on the back of a house in a conservation area is usually allowed, while one on the street-facing front or side is not.

What changes in Camden: Article 4 directions

Councils can go further and remove permitted development rights in particular areas with an Article 4 direction. Camden has Article 4 directions covering, among others, the Belsize, Hampstead, Fitzjohns Netherhall, Redington and Frognal, Primrose Hill and South Hampstead conservation areas. Each direction lists exactly which rights it removes, so check the one for your street before planning any work on the outside of the house.

The West End Green Conservation Area in West Hampstead is not on Camden’s Article 4 list, so the standard conservation area rules above apply there.

Flats and listed buildings

Flats have no permitted development rights of this kind at all. A new flue through the outside wall of a flat, or a new soil pipe on a block, normally needs planning permission and the freeholder’s consent.

Listed buildings need listed building consent for most changes that affect their character, inside or out. Several houses on Chalcot Square in Primrose Hill, and many others across NW3, are listed. Speak to Camden’s planning team before you commit to a route.

A quick guide

Your situation	Likely answer
Boiler repair, flue unchanged	No permission needed
New flue on the rear wall of a house	Usually permitted development
New flue on a street-facing front or side wall, conservation area	Planning permission needed
Any new external flue on a flat	Planning permission needed
Any external change to a listed building	Listed building consent likely
Flue more than a metre above the roof	Planning permission needed

Planning a flue route

If a boiler needs replacing, ask your installer for a flue route at the back of the house first, or one hidden from the street, before anything changes on the outside. We do no gas work ourselves, but new soil and waste pipes follow the same rules, and we plan their routes the same way.

If your hot water has stopped, our guide to no hot water covers the first checks, or call 07862 142953.