Enfield has the rule in a planning policy, not just a leaflet. DMD 11 sets depths, heights and two sight lines. We draw them on your plan so the officer can check them in one look.
Photo: A P Monblat, BY-SA 3.0
Policy DMD 11 in the Development Management Document, adopted in November 2014, is Enfield's rear extension policy. It starts with three conditions: no harm to the amenity of the original building and its neighbours, adequate garden and access to garages or parking kept, and no adverse visual impact.
For a single storey it then sets numbers. The extension must not exceed 3 metres beyond the original rear wall in the case of terraced and semi-detached properties, or 4 metres for detached dwellings. A flat roof should not exceed 3 metres to the eaves, with 3.3 to 3.5 metres allowed to the top of a parapet. A pitched roof should not exceed 4 metres to the ridge and 3 metres at the eaves. It must also either stay inside a line at 45 degrees from the mid-point of the nearest original ground-floor window of any adjacent property, or secure a common alignment with neighbouring extensions.
At first floor the test is tighter: a first-floor extension must not exceed a line at 30 degrees from the mid-point of the nearest original first-floor window of any adjacent property, and where appropriate secure a common alignment. Both lines come from the neighbour's original windows, not from any later alterations, so the survey has to establish which windows are original.
Four numbers decide most Enfield rear extension drawings.
| Part of the extension | DMD 11 rule | What we draw |
|---|---|---|
| Depth, terrace or semi | Not more than 3 metres beyond the original rear wall | Dimension from original wall |
| Depth, detached | Not more than 4 metres beyond the original rear wall | Dimension from original wall |
| Ground floor sight line | Within 45 degrees from the nearest original window next door | Line on the plan |
| First floor sight line | Within 30 degrees from the nearest original first-floor window | Line on the first-floor plan |
Enfield Council, Development Management Document, policy DMD 11, adopted November 2014.
The fee includes our measured visit. The bracketed figure applies if you already have measured drawings.
Enfield has 22 conservation areas, and its conservation page explains that the council may issue an Article 4 direction where particularly important features need protecting. Where one applies you must submit a planning application for certain works that would not normally need one, so look up your street before assuming the permitted development depth.
For example, a semi in Winchmore Hill that fits the 3 metre depth and the 45 degree line may meet both DMD 11 and the Class A limits, so a lawful development certificate could prove it. The same design a metre deeper meets neither and needs a householder application.
Enfield's CIL charging schedule, effective 1 April 2016, has three residential zones, with a nil rate in the Meridian Water masterplan area. Whether CIL arises on an extension depends on its floor area, so we measure it before you commit. Enfield decided 920 householder applications in the year to June 2026 once prior approvals are set aside, 851 of them inside 8 weeks.
Every figure is linked to the page or document we read.
Enfield's policy DMD 11 (November 2014) says a single-storey rear extension must not exceed 3 metres beyond the original rear wall on terraced and semi-detached properties, or 4 metres on detached dwellings.
Source: Enfield Council, Development Management Document, policy DMD 11DMD 11 sets a 45 degree line from the nearest original ground-floor window next door for single-storey extensions, and a 30 degree line from the nearest original first-floor window for first-floor extensions.
Source: Enfield Council, Development Management Document, policy DMD 11DMD 11 limits a pitched-roof single-storey extension to 4 metres at the ridge and 3 metres at the eaves, and a flat roof to 3 metres at the eaves.
Source: Enfield Council, Development Management Document, policy DMD 11Enfield has 22 conservation areas, and may issue an Article 4 direction to protect important features within them.
Source: Enfield Council, Conservation areasEnfield's CIL charging schedule took effect on 1 April 2016 and sets 3 residential rate zones, with a nil rate in the Meridian Water masterplan area.
Source: Enfield Council, Community Infrastructure Levy Charging Schedule, April 2016Enfield decided 920 householder applications between July 2025 and June 2026, prior approvals excluded, and 851 of them were decided within 8 weeks.
Source: MHCLG, Planning application statistics PS2, July 2025 to June 2026Permitted development allows a single-storey rear extension up to 4 metres on a detached house or 3 metres on any other house.
Source: legislation.gov.uk, GPDO 2015, Schedule 2, Part 1, Class ATell us about your project and get a fixed, no-obligation quote back within one working day. If you don't need planning permission at all, we'll tell you that too — for free.
Policy DMD 11 says a single-storey extension must not exceed 3 metres beyond the original rear wall on a terraced or semi-detached house, or 4 metres on a detached house, and must stay inside the 45 degree line from the neighbour's nearest original window unless it secures a common alignment.
DMD 11 says a first-floor extension must not exceed a line taken at 30 degrees from the mid-point of the nearest original first-floor window of any adjacent property, and where appropriate it should secure a common alignment of rear extensions.
For a flat roof, DMD 11 says no more than 3 metres to the eaves, with 3.3 to 3.5 metres allowed to the top of a parapet wall. For a pitched roof, no more than 4 metres to the ridge and 3 metres at the eaves.
Enfield has 22 conservation areas and says it may issue an Article 4 direction to protect important features. Its conservation page links the directions. Where one applies, certain works that would not normally need permission do.
£765 inc survey (£565 if you supply measured drawings). That covers the measured survey, the drawings and the submission, with free revisions until the council decides. Enfield's own application fee is separate and goes to the council.
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