Boilers and heat pumps ยท In brief
Boiler flue position and plumes in terraced streets
Boiler flue position regulations require outlets that let combustion products disperse; Approved Document J gives Diagrams 34 and 35 as one way to comply. A Gas Safe registered engineer decides the position on the job.
Most useful for: Terraced neighbours and anyone planning a new boiler flue
Compiled from the sources at the end. Updated .
This page gives no clearance distances. They depend on openings, boundaries and the particular wall, so a number lifted from somewhere else is unlikely to fit your house. Ask the engineer to show which part of the diagrams they are working to.
Para 3.23 of Approved Document J also carries a note that matters in tight streets: condensing boiler plumes can be a nuisance to neighbours even at compliant distances. So a flue can meet the diagrams and still blow vapour across a neighbour's window or yard.
Do not assume a council officer will review the position either. Under para 3.1, a gas-appliance-only installation by a member of the approved class need not be notified to Building Control, so the conversation with the engineer is where this gets settled.
Why terraces make this harder
Terraced houses north of Mill Road stand directly on the pavement, and Newnham Croft terraces have small fronts and long thin back gardens. In layouts like these, the likely routes for a flue can be limited and close to the next house. Raise the plume with the engineer before the hole is drilled, and it can help to tell your neighbour early as well.
If you are worried about a flue
HSE says flues must be in a safe position at specified distances, and that if you are concerned you should get a Gas Safe engineer to examine it. Do not touch or alter a flue yourself. If you suspect carbon monoxide or smell gas, leave the checks and follow the emergency steps.
A flue through a listed building may need consent. South Cambridgeshire's 2009 guidance says that if flues are required, consent may be necessary, and that wording is not a yes or no. Ask the conservation officer first, and see listed building consent for heating. The rest of the job is on the boiler replacement page.
Sources, read 4 November 2026: Approved Document J, 2022; HSE, gas safety FAQs; South Cambridgeshire Listed Buildings SPD, 2009; Mill Road Conservation Area Appraisal, 2011; Newnham Croft Conservation Area Appraisal, 2013.