Neighbour's extension blocking light: daylight, sunlight and overshadowing

An extension can affect the natural light reaching a neighbouring home or garden. The useful planning question is what changes for the particular space, and whether that change is acceptable in its setting. A new shadow or a larger wall does not, by itself, answer that question.

Start with the current application drawings and identify the room, window or part of the garden concerned. You can explain a factual concern without calculating a daylight score. Say what you know, show its source and leave unknown information marked as unknown.

Daylight, sunlight, overshadowing and enclosure

Daylight is natural illumination from the sky. Sunlight means direct sunshine. A room can receive daylight when the sun is not shining directly into it. Overshadowing describes an obstruction blocking sunshine from a window or outdoor space.

Enclosure concerns the surrounding built relationship: for example, a wall or roof dominating the outlook from a room or sitting area. It needs its own explanation. A daylight finding does not establish whether an outlook is acceptable. See the privacy, outlook and overbearing evidence resource for those related issues.

Can a neighbour's extension block too much light?

Loss of light can be a planning consideration. For a current England application, check the applicable development plan and national policy. The National Planning Policy Framework published on 17 August 2026 addresses access to light and neighbouring daylight and sunlight in P3(2)(a)-(b). It provides no universal percentage for deciding every neighbour's extension.

A reduction can be noticeable without being judged unacceptable. In the historical South Hams appeal included in our comparison, the Inspector accepted a noticeable change after considering the assessment and the affected room's other windows. Other decisions found harmful light effects. Read the nine daylight and overshadowing decisions to compare the evidence and limits, rather than treating an outcome as a rule for your application.

Why the affected room and window matter

Write down the room's use and which window you mean. Record other windows or glazed doors serving that same room, if known. A photograph of one opening may not show the room's full relationship with the proposal. Equally, another window's existence does not automatically resolve the concern.

Distinguish your own observations from assumptions about someone else's layout. If the application assessment labels a window differently from how your room is used, identify the label, explain the discrepancy and ask for it to be checked. Do not infer that a bedroom is irrelevant because it is not a living room. The Camden decision in the comparison illustrates why room use can remain an important uncertainty.

Look at the proposed wall, roof and any new floor above it. Which part faces the window? Do elevations or sections show its height and the relevant ground or floor levels? Record drawing numbers and revisions. Do not combine a height from an old plan with a footprint from its replacement.

Orientation, levels and existing obstructions

Note the direction the affected window faces where you can establish it. Use the submitted north arrow if available and explain your source. A description such as 'the extension is beside my kitchen window' is useful; an unsupported claim about how much winter sunlight it removes is not a calculation.

Compare existing and proposed conditions. An existing extension, boundary wall, balcony, roof or tree may already affect the relationship. Note it rather than assuming the current space is unobstructed. A proposed extension can replace something already there, increase it or occupy a new position. Those differences can matter.

Record level changes shown on a section. A boundary plan alone may not explain a higher roof on sloping land. If the relevant section is absent or unclear, state the information gap and ask the officer to assess it. Do not invent ground levels or derive a precise dimension from an unscaled screenshot.

Gardens and outdoor amenity space

Identify the outdoor area affected: a private patio, a small rear garden or a shared garden, for example. Explain which part you mean and the proposed feature that would cast additional shadow there. Describe existing conditions with dates and approximate times if you have observations.

A photograph of a shadow at one moment records that moment. It does not establish the whole day's sunlight, a seasonal pattern or the proposed development's future effect. Label observations clearly and avoid claiming they substitute for an assessment. Where a shadow study is available, check whether it actually covers your outdoor space, its stated dates and the correct proposal revision.

What to look for in a daylight or sunlight report

An application may contain a specialist assessment. Its existence is not proof that every affected room or garden has been assessed. Start with its site plan, window or room labels, proposal revision and the locations included. Look for an explanation of existing conditions, proposed conditions, assumptions and conclusions.

Raise a concrete omission rather than asserting that a report must be wrong. For example: 'The report identifies rear window W4, but I cannot find the shared garden marked on my note. Please clarify whether the garden's sunlight has been assessed.' You do not need to reproduce the report or perform your own technical calculations to ask that question.

National policy calls for proportionate information. The historical examples include both an unresolved evidence gap and a case where the Inspector could assess the relationship without a detailed report. Neither establishes that every house extension needs a report, or that reports can always be dispensed with.

BRE guidance and angle tests

BRE's BR 209, 2022 edition, is technical guidance on daylight and sunlight. Its publisher describes it as advisory and allows contextual variation in its numerical targets. The full standard requires licensed access; this guide does not reproduce its calculations or target tables.

Councils may refer to that guidance and publish their own approach. Check the actual local document, its date and the purpose of any test. A screening exercise, a report requirement and a final judgment about amenity are different things. Avoid treating an angle drawn on a plan as an England-wide pass or fail rule.

The Camden council resource and Hackney council resource provide local starting points. Check their current official sources and the policy area covering the site. NeighbourObjection provides document preparation; it does not carry out technical daylight or sunlight assessments.

A practical evidence checklist

You can prepare a short note using these prompts. 'Unknown' is an acceptable entry.

• Application: reference, application type, decision status and actual comment deadline.
• Drawings: existing and proposed plan, elevation and section numbers, dates and revisions.
• Affected room: use of the room, affected window and any other windows serving it.
• Relationship: proposed wall or roof, orientation and relevant levels where established.
• Existing obstructions: buildings, walls, overhangs or planting that help explain the baseline.
• Outdoor space: the particular garden or sitting area and its position relative to the proposal.
• Observations: photographs taken lawfully from your own property or a public place, labelled with date, approximate time and viewpoint where useful. Avoid unnecessary people or private household detail.
• Submitted assessment: title/date, relevant window or garden label, assumptions you cannot confirm and any clear mismatch with the drawings.
• Request: the light effect you want assessed and any specific information needed to understand it.

Use the application and evidence checklist for the wider submission task. Keep source labels with measurements: submitted drawing, your measurement, estimate or unknown. A simple location sketch is explanatory evidence, not a professional light model.

A factual comment structure

Fictional example: 'Drawing A104 revision C shows the proposed rear wall alongside the kitchen window marked K1 on my note. This room also has rear doors, shown on my sketch. The submitted section does not clearly show the relative window and roof levels. Please assess the effect on daylight to the kitchen and clarify the relevant levels.'

For a garden concern, identify the outdoor area and the change instead. Keep an enclosing outlook as a separate point, explaining the wall or roof visible from that space. Use your own evidence; do not copy the fictional facts into an unrelated application.

Planning light concerns and a private right to light

Planning amenity and a private legal right to light are separate questions. A planning comment should explain the proposal's effect on living conditions. It should not claim that a private right has been established merely because a window loses light. This guide does not determine private rights or provide legal advice.

Property value, private boundary disputes and a wish to keep an attractive private view should not substitute for a supported planning concern. Read how planning decisions weigh neighbour comments and deadlines and late comments before sending your representation. The customer reviews and submits any NeighbourObjection draft themselves.