A rear extension refused on daylight, then approved

An extension refused on daylight and then approved usually gets there through one change, not a redesign. In the illustrative case below, a 4 m deep single-storey rear extension on a Victorian semi was refused for loss of light to the neighbour's kitchen window, and a revised scheme at 3.2 m with a lowered eaves and a pitched roof falling away from the boundary was approved four months later. The scheme, the dimensions and the sequence are illustrative and are not drawn from any real application.

The change that mattered was 800 mm of depth and 400 mm of height. Everything else in the resubmission was presentation.

The original scheme and the reason for refusal

The host dwelling was a two-storey Victorian semi-detached house with a small existing rear outrigger. The proposal was a full-width single-storey rear extension, 4 m deep, with a flat roof at 3 m to the parapet, running hard to the shared boundary.

The neighbouring house had a ground-floor kitchen window in its rear elevation, roughly 1.8 m from the boundary, serving the only habitable room on that side at ground level.

The single reason for refusal was loss of daylight to that window, contrary to the local plan's residential amenity policy and the council's householder design guide. There was no objection to the design, the materials or the loss of garden. One reason, one window.

Reading the officer report properly

The delegated report is the most useful document in the process and most applicants skim it. Read it three times and mark three things.

First, the test the officer actually applied. Here it was the 45-degree rule from the council's own design guide, taken in both plan and section from the centre of the neighbour's window. Second, what the officer said was acceptable, which in this report was an extension of similar depth on the other flank where there was no habitable window. Third, the phrasing of the harm: the report said the extension "would breach the 45-degree line in section by a substantial margin", which told the applicant the vertical dimension was in play as much as the depth.

Nothing in the report mentioned the numerical daylight tests in the British Research Establishment guidance. That absence was itself information. The council was applying a geometric rule of thumb, so the answer was geometric.

Our note on the 45-degree rule and how councils test loss of light sets out how the plan and section tests are taken.

What the daylight evidence actually showed

The applicant commissioned a technical assessment after the refusal rather than before, which is the wrong order but a common one.

The results were more favourable than the refusal implied. The vertical sky component at the centre of the neighbour's window fell below the guidance value of 27 per cent, but the reduction relative to the existing condition was close to the 0.8 times ratio that the guidance treats as the point at which loss becomes noticeable. Annual probable sunlight hours were unaffected, because the window faced north-east.

That produced an awkward position. The scheme failed the council's geometric rule clearly, and was borderline on the technical tests the guidance uses. Arguing the technical case alone would have meant asking a committee to prefer a consultant's modelling over its own adopted design guide, which rarely succeeds at householder scale.

So the technical assessment was used differently: to identify the smallest change that would bring the scheme within the geometric rule. A daylight and sunlight assessment used as a design tool is worth more than one used as an argument.

The design change that resolved it

Three changes, in order of effect.

1. Depth reduced from 4 m to 3.2 m, measured from the original rear wall.
2. Flat roof replaced with a shallow mono-pitch falling away from the shared boundary, with the eaves at 2.6 m on the boundary side.
3. The last 1.2 m of the extension adjacent to the boundary set in by 700 mm, creating a stepped rear elevation.

The set-in was the change the applicant resisted and the one the officer valued most, because it moved the mass out of the 45-degree cone in plan as well as section. Internally it cost a corner of the utility space and nothing else.

The kitchen the client wanted was still deliverable. Losing 800 mm of depth across the full width removed about 3 m2 of floor area, and the rooflights in the new pitched roof more than compensated for the daylight in the extended room itself.

Dimensions here are illustrative.

Neighbour engagement second time round

The neighbour had objected to the first application in strong terms, and their objection was quoted in the officer report.

Before the resubmission the applicant took the revised drawings round in person, with the section drawing showing the 45-degree line and the new roof profile on the same sheet. The neighbour did not withdraw their earlier objection formally, but they did not object again. That silence changed the tone of the second report.

This is worth doing even where you expect no goodwill. An officer writing a delegated report on a resubmission with no fresh objection has an easier decision to justify than one facing a repeated objection. And where amendments are made after an objection, the consultation position can shift, and a worked version of the geometry is set out in the 45-degree rule rear extension worked example.

The fee position on a resubmission

A concession historically allowed one repeat application without a further fee, where it followed a refusal or withdrawal on the same site by the same applicant for development of the same character and description, and was submitted within twelve months.

The fee regulations were amended in December 2023 and fees have been indexed annually since April 2025. Check the current fee schedule with the council or the Planning Portal fee calculator before assuming any exemption applies, because this is exactly the kind of provision that changes without much notice. Where an exemption does apply, it applies once, so a third application carries a fee.

Twelve months is the relevant clock in any event. A resubmission prepared quickly, while the officer still remembers the site, is worth more than a perfect one submitted eleven months later.

The approved scheme compared with the first

The second application was determined under delegated powers in seven weeks. The report ran to two pages and turned on a single paragraph confirming that the revised form complied with the 45-degree test in plan and section.

Two conditions were attached: materials to match the host dwelling, and the rear boundary-side rooflight to be obscure glazed. Neither had appeared on the first refusal.

The lesson is narrow and useful. Where refusal turns on a geometric rule the council has adopted, the quickest route back is to comply with the rule, not to challenge it. Save the technical case for schemes where the council has no adopted rule and the argument is about light rather than about geometry.

For the underlying method on terraced and semi-detached rear extensions, see daylight for a rear extension in a Victorian terrace. The supporting planning statement for a resubmission should address the refusal reason first and everything else second.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it.