Loss of light refusals and the tests inspectors use

A loss of light planning refusal almost never rests on a daylight calculation. On a householder application it usually rests on a line drawn at 45 degrees from the neighbour's nearest habitable room window, taken from the council's own design guide, and on the officer's view of how enclosing the extension will feel from inside that room. Those are two separate allegations, and an appeal that answers only the first tends to fail. Work out which line the council applied, get the section drawn properly, and you will know within an afternoon whether the refusal is arguable.

What the refusal is really alleging

Decision notices bundle three things together under residential amenity. Loss of daylight is about the total amount of skylight reaching a window. Loss of sunlight is about direct sun, and it matters mainly to windows and gardens facing within 90 degrees of due south. Overbearing effect, sometimes written as loss of outlook or sense of enclosure, is about how dominant the new structure looks from the neighbouring window or garden, and there is no numerical test for it at all.

Read the reason and separate them. If the notice mentions dominance or enclosure, no amount of daylight modelling will dispose of it.

Officers also distinguish habitable rooms from the rest. A kitchen, living room, dining room or bedroom is protected. A bathroom, hallway, landing, utility room or garage is generally not, and neither is a conservatory in most authorities' guidance. If the window the objection concerns serves a bathroom, say so in the first paragraph of your appeal statement.

Where the 45 and 25 degree tests come from

The 45-degree test is a local design guide convention, not national policy. It is applied in two dimensions. In plan, a line is drawn at 45 degrees from the centre of the neighbour's nearest habitable room window towards the boundary. In section, a line is drawn at 45 degrees from the same window, usually from the centre or from the head of the window depending on the guide. Councils vary on whether breaching one line matters or whether both have to be crossed, which is exactly why you need to read the local document rather than a general summary.

The 25-degree test comes from BRE 209, Site Layout Planning for Daylight and Sunlight, in its 2022 edition. It is measured in section from a point 2 m above external ground level at the centre of the lowest affected window. If the new development subtends an angle of less than 25 degrees to the horizontal from that point, enough skylight is likely to remain and no further calculation is needed. Cross the line and the assessor moves on to the detailed measures.

BRE 209 is guidance for designers, and its own introduction says the numerical targets are flexible and should be applied with judgement about context. Inspectors quote that flexibility in dense urban settings. In a suburban street with generous spacing it cuts the other way, because the existing standard of amenity is high and a large reduction is harder to excuse.

Section drawings decide the case

Most loss of light refusals on extensions could have been avoided by one properly drawn section. It needs the neighbour's window in it, at a real height above a surveyed ground level, with the proposed extension shown against it and the 45 and 25 degree lines drawn and labelled.

1. Survey the neighbour's ground level and the sill and head heights of the affected window from your side of the boundary.
2. Draw the section along the line between that window and the nearest part of the extension, not along the easiest line on the plan.
3. Fix a datum and put it on the drawing, so ridge, eaves and neighbouring ground level can all be read together.
4. Plot both lines from the point the local guide specifies and state which guide you used.
5. Show the existing situation on the same sheet, including any existing outbuilding or boundary wall already obstructing the window.

Point five earns its place more often than people expect. Where a 2 m close-boarded fence and a mature hedge already sit between the window and the boundary, the extension's marginal effect is small, and that is a fact the section can prove and prose cannot.

Overbearing effect as a separate matter

There is no threshold for dominance, which makes it the hardest limb to answer and the easiest for an authority to assert. What works is showing the change in the field of view from inside the neighbouring room, using a section and an elevation taken from that window position, plus the distance from the window to the new wall and the height of that wall above the neighbour's eye level.

Design changes that reduce it are usually simple. Pull the flank wall back from the boundary by half a metre. Drop the eaves and use a hipped or pitched roof falling away from the boundary. Reduce the projection at the boundary and step the rear wall out further away from it. Each is worth more than an argument.

Rights of light compared with planning

These are different systems and they produce different answers. Rights of light is a private property matter, acquired over 20 years under the Prescription Act 1832 or by deed, and enforced in the civil courts with remedies including an injunction or damages. It is not a planning consideration, and a council cannot refuse permission because a neighbour has a right of light, nor grant permission that overrides one.

The practical consequence is that a permission does not protect you. If your extension would infringe a right of light your neighbour can still pursue it after you build, so on a tight urban boundary take advice before starting work rather than after. The Party Wall etc. Act 1996 is a third separate regime, again not a planning matter, and it applies to excavation near and work on a shared wall.

What to submit on appeal

A householder appeal must be lodged within 12 weeks of the decision notice, and the householder appeals service decides on the documents already before it. There is no second round of submissions, so everything has to be in the appeal statement on day one. Put the section drawing first, the local guide extract second, and the argument third.

Two other points carry weight. If a smaller version of the extension could be built without permission under Class A of Part 1 of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015, show what that fallback looks like in section, because an inspector comparing your proposal with a lawful alternative sees the real difference in effect. And if you have already reduced the scheme once in response to the officer's comments, evidence the sequence rather than describing it. Where the remaining dispute is narrow, resubmitting a refused scheme instead of appealing is often faster than 12 to 20 weeks of appeal, and deciding whether a refusal reason is worth appealing sets out how to weigh the two.

The policy argument sits in the Planning Statement, and on a householder scheme that document can be short, three or four pages tying the section drawing to the amenity policy and the design guide. PlanScope drafts one from your answers and the site constraints and marks missing site facts rather than assuming them, which matters when a surveyed neighbouring ground level is the fact the case turns on. The wider pattern of small-scheme failings is covered in why householder applications are refused most often.

Draw the section before you draw anything else. It is the least expensive piece of evidence in a loss of light case and the only one that settles the argument.

Enter your postcode on PlanScope to see which documents your extension application is likely to need.

This is general guidance, not legal advice, so check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.