The 6-Metre Extension: How Many London Homeowners Use Prior Approval, Which Boroughs Refuse the Most, and Where the Neighbours Object — Nine Months of Government Data
By Anderson & the LCCL Construction Team | Finchley N3
Finchley, 11 November 2026. A single-storey rear extension of up to 3 metres on a terraced or semi-detached house (4 metres on a detached house) is permitted development: no application, a Lawful Development Certificate if you want the position in writing. Beyond that, up to 6 metres (8 on a detached house), the law offers a halfway house called prior approval: you notify the council, the council writes to the neighbours, and if nobody objects within 21 days the extension goes ahead without a planning application. If a neighbour does object, the council decides on amenity grounds alone. The government publishes, every quarter, how many of these notifications each council receives and what happened to them. This piece puts nine months of that data together for London and Hertfordshire, which as far as we can find nobody has done.
As LABC Building Excellence Award Winners 2024 for Best Residential Extension in London — and London Regional Winner 2026 for Best Conversion or Alteration to an Existing Home — we build 3-metre and 6-metre rear extensions across London and Hertfordshire — the Holmwood Gardens N3 extension in the photograph is a full-width single-storey rear extension of the kind most of these notifications describe — and we run the prior-approval notification ourselves on every larger extension we design. We have an interest in the route; the figures below are the government's, not ours.
Not sure whether your project needs planning permission? Enter your postcode and tick what you want to build — about two minutes, free, and the from-price for each part that qualifies appears on screen and in your inbox.
What the data is, and what it is not
The figures come from the ministry's PDR1 return, the quarterly table in which every district planning authority in England reports its prior-approval decisions by type. We have added the three most recent quarters — October to December 2025, January to March 2026 and April to June 2026 — for the category the table calls larger household extensions. Each notification ends one of three ways: "prior approval not required", which means no neighbour objected and the extension can proceed; "granted", which means a neighbour objected and the council approved it anyway; or "refused", which means a neighbour objected and the council agreed the extension would harm their amenity. We treat "not required" and "granted" together as successes, and the sum of "granted" and "refused" as the share of cases where a neighbour objected.
Two cautions. Nine months is not a year: the July to September 2025 table is not available in the form the others are, so the figures cover 1 October 2025 to 30 June 2026 and we say so wherever a number appears. And councils do not all record the same way: Greenwich and Richmond report every case as "granted" or "refused" and none as "not required", which almost certainly reflects how they log the decision rather than a borough where every neighbour objects. Where that affects a ranking we flag it.
London: the headline
London's 33 boroughs decided 3,398 larger-extension notifications in the nine months: 2,212 went through with no objection (65 per cent), 410 were approved after an objection (12 per cent) and 776 were refused (23 per cent). Put another way, a neighbour objected in roughly one case in three, and when they did the council sided with the neighbour two times in three. Across England the picture is gentler: 9,079 notifications, 68 per cent with no objection, 18 per cent refused. London's refusal rate is a quarter higher than the country's, which is what you would expect where gardens are shorter and houses closer together.
Larger extensions dominate the prior-approval system in the capital: of 4,046 prior-approval notifications of every kind that London boroughs decided in the period, 3,398 — 84 per cent — were for a rear extension. In England as a whole the share is 54 per cent. Prior approval in London is, in effect, the 6-metre extension.
The busiest boroughs
Redbridge — 375 notifications in nine months, the most in London; 72 per cent went through unopposed, 20 per cent refused.
Harrow — 300; 68 per cent unopposed, 26 per cent refused.
Enfield — 261; 80 per cent unopposed, 8 per cent refused.
Barking and Dagenham — 210; 87 per cent unopposed, 10 per cent refused.
Ealing — 208; 68 per cent unopposed, 26 per cent refused.
Barnet — 182; 47 per cent unopposed, 45 per cent refused.
Hounslow — 180; 73 per cent unopposed, 19 per cent refused.
Brent — 169; 63 per cent unopposed, 36 per cent refused.
The outer boroughs of 1930s semis — Redbridge, Harrow, Enfield, Barking and Dagenham, Havering, Hillingdon — are where the 6-metre extension is most used, which follows from the housing: a semi with a 20-metre garden can take 6 metres and still keep a lawn. The inner boroughs barely appear. Camden decided five notifications in nine months, Islington three, Hammersmith and Fulham two, and Kensington and Chelsea, Westminster and the City of London none at all, because conservation areas cover most of their housing and the larger-extension route is not available on conservation-area land.
Where it gets refused
Lewisham — 84 notifications, 42 refused (50 per cent); no case recorded as approved after an objection.
Barnet — 182, 81 refused (45 per cent) — the highest refusal count in London, and consistent across all three quarters (24, 25 and 32).
Greenwich — 135, 59 refused (44 per cent); records no "not required" cases, so the rate is overstated against boroughs that do.
Brent — 169, 61 refused (36 per cent).
Waltham Forest — 158, 48 refused (30 per cent).
Merton — 148, 42 refused (28 per cent).
Richmond upon Thames — 72, 20 refused (28 per cent); records every case as granted or refused, like Greenwich.
And the boroughs where the route almost always works: Hillingdon refused 4 of 94 (4 per cent), Bexley 5 of 63 (8 per cent), Enfield 21 of 261 (8 per cent), Barking and Dagenham 20 of 210 (10 per cent) and Havering 18 of 168 (11 per cent). In Enfield four notifications in five go through without a neighbour saying a word.
Hertfordshire
The ten Hertfordshire districts decided 350 larger-extension notifications in the nine months, with a lower objection rate than London almost everywhere. Watford is the exception: 59 notifications, 17 refused (29 per cent) — a London refusal rate in a Hertfordshire town, which fits its tight Victorian streets. St Albans (53 notifications, 21 per cent refused), Three Rivers (53, 13 per cent) and Hertsmere (55, 22 per cent) sit in the middle. Dacorum refused 2 of 30, Broxbourne 3 of 29, East Hertfordshire 2 of 21 and North Hertfordshire none of 12.
What the numbers mean if you are planning one
First, the route works far more often than it fails: across London 77 per cent of larger-extension notifications end with the extension allowed, and in the outer boroughs where most of them are made it is 80 to 90 per cent. Second, the borough is not the decisive factor — the neighbour is. A refusal only happens after an objection, and an objection is far less likely when the neighbour has seen the drawings before the council's letter arrives; our team gives every client a neighbour letter and a copy of the drawings to hand over before the council's letter arrives, for that reason. Third, the refusal rates in Barnet, Lewisham, Brent and Greenwich are high enough that on a short garden or a close neighbour the question is worth asking before the drawings are finished: is the extra metre or two beyond 3 metres worth a one-in-three to one-in-two risk of refusal and a redesign, or does a 3-metre extension — permitted development, no notification, no neighbour consultation — give the room you actually need? On a 5-metre-wide terrace the difference between 3 metres and 4.5 is seven square metres.
Anderson's advice
Decide the depth from the garden, not from the allowance. The 6-metre figure is a ceiling, not a target: most of the kitchen-diners we build are 3 to 4 metres deep, because beyond that the middle of the room goes dark without rooflights and the garden that is left stops being a garden. Our team draws the 3-metre version first and shows the client what the extra depth buys before anyone notifies a neighbour. Where the extra depth is right — a long garden, a family that wants a dining room as well as a kitchen — the neighbours see the drawings before the council writes to them, because an objection costs eight weeks and a refusal costs the summer.
What our clients say
“We did a 3x10m single storey rear extension with LCCL recently. It was scheduled to take 12 weeks to complete but with Alex's experience and agile project management, we are ahead of schedule (finished in 10). Alex, and LCCL,is extremely knowledgeable and will work with you explaining what can, and cannot, be done and why. He works magic in harmonising between the different trades and chooses extremely serious and rigorous builders. With Alex, you know no corners will be cut: your house will be sturdy, warm, waterproof, and will look nice, making you (and Alex himself) feel proud of the job. without doubt, I would choose LCCL again for any future building project.”
— Galichet Christophe, Google Reviews
Method and sources
Source: Ministry of Housing, Communities and Local Government, Planning applications in England, live tables, Table PDR1 — district planning authorities, applications for prior approvals for permitted developments, by local planning authority — for the quarters October to December 2025, January to March 2026 and April to June 2026 (the latest release, published 24 September 2026; the earlier quarters from the archived versions of the same table). Category: larger household extensions. "Successes" = prior approval not required + granted; "objected" = granted + refused; refusal rate = refused ÷ all decisions. London = the 33 boroughs including the City of London; the borough totals reconcile to the London row in each quarter. The July to September 2025 table could not be obtained in a consistent form, so the period is nine months and every figure is labelled as such. Greenwich and Richmond upon Thames record no "not required" decisions in any quarter; their refusal rates are not comparable with boroughs that do. All prior-approval types: Overall total row of the same tables. A correction or a query about any figure can be sent to info@lcclconstruction.co.uk and will be answered on this page.
Frequently asked questions
How often is a 6-metre extension refused in London?
In the nine months to June 2026, 23 per cent of larger-extension prior-approval notifications in London were refused, against 18 per cent across England. The spread is wide: under 10 per cent in Hillingdon, Bexley and Enfield, 45 per cent in Barnet and 50 per cent in Lewisham. A refusal can only follow a neighbour objection, and in two cases out of three no neighbour objected at all.
What is the difference between a 3-metre and a 6-metre rear extension?
A single-storey rear extension up to 3 metres deep on a terraced or semi-detached house (4 metres detached) is permitted development with no application or neighbour consultation. Between 3 and 6 metres (4 to 8 detached) it goes through prior approval: a notification to the council, a 21-day neighbour consultation and a 42-day decision period. Both must stay under 4 metres high, with eaves no higher than 3 metres within 2 metres of a boundary, and neither route is available in a conservation area.
Do I need planning permission for a rear extension in Barnet or Lewisham?
Not for a 3-metre extension on a house outside a conservation area — that is permitted development, confirmed with a Lawful Development Certificate. For 3 to 6 metres the prior-approval route is open in both boroughs, but the data shows Barnet refused 45 per cent and Lewisham 50 per cent of those notifications in the nine months to June 2026, so a neighbour conversation before the drawings are finished matters more there than anywhere else in London. The council has the final say.
Check your own house
Not sure whether your project needs planning permission? Enter your postcode and tick what you want to build — about two minutes, free, and the from-price for each part that qualifies appears on screen and in your inbox.
To talk through a 3-metre or 6-metre rear extension anywhere in London or Hertfordshire, book a free 30-minute consultation call with LCCL Construction on 020 8037 7332, or get an instant estimate in about two minutes. How the route works is explained in the 6 m and 8 m rear extension without planning permission and what happens when the neighbours object.
One team, one contract, one point of contact — from first sketch to handover.
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