Daylight and Sunlight in Planning
How daylight and sunlight is considered in in planning applications: the BRE and British Standard tests, NPPF and local plan policy, when technical reports are needed, and right to light.
PLANNING APPLICATIONS
Andrew Ransome
10/7/20265 min read
Daylight and sunlight are among the most common grounds of objection to housing and extension schemes, and among the most technical.
Neighbours raise them, case officers pick them up, and inspectors weigh them on appeal. This guide explains what is actually being assessed, which policies apply, and when specialist technical work is needed.
Daylight and sunlight are not the same thing
The two terms are often used interchangeably, but they measure different things.
Daylight is the natural light that reaches a room from the sky generally, and how bright and usable a space feels as a result.
Sunlight is the direct light from the sun, and how much of it a window or open space receives over the day and the year.
A scheme can affect one without affecting the other. It can also affect two different groups:
the neighbours whose windows and gardens sit next to the development, and
the future occupiers of the new development itself.
A full assessment may need to look at both.
What the policy says
National policy
Two policies in the NPPF are directly relevant.
Policy P3 (living conditions and pollution) says development should not give rise to, or contribute to, an unacceptable level of access to daylight and sunlight for neighbouring residents and occupiers. Adverse impacts should be avoided where possible, or mitigated to an acceptable degree.
Policy L2 (making effective use of land) applies to additional development within existing residential curtilages, and to upward extensions and similar proposals. Among other requirements, these should maintain acceptable living standards for residents and neighbours in terms of access to daylight, sunlight, privacy and external amenity space.
Neither policy sets a numerical standard. They set the test and leave the measurement to guidance and judgement.
Local plan policy
Most development plans have their own residential amenity policies that cover daylight and sunlight, usually alongside privacy, outlook and overbearing impact.
Authorities take different approaches:
Some refer expressly to the BRE guidance or the British Standard in policy or supplementary guidance.
Some use general language such as "unacceptable harm to residential amenity" and leave the method to the case officer.
Some, particularly in dense urban areas, have more detailed expectations about the information that should accompany an application.
It is worth reading the local policy before deciding how much technical work a scheme needs.
Under policy DM2, local validation lists should only require additional information where a development plan policy calls for it, and the requirement should be proportionate to the scale of development and its potential impact.
A daylight and sunlight report is therefore more likely to be required for a larger or tighter scheme, but the local validation list is the place to check.
How daylight and sunlight are assessed
Two non-mandatory technical sources are normally used.
The first is the BRE guide, Site Layout Planning for Daylight and Sunlight, which was comprehensively revised in 2022.
The second is British Standard BS EN 17037:2018+A1:2021.
Neither is mandatory.
The BRE guide does not supersede the British Standard; they are alternative approaches rather than a hierarchy. The guidance is also just that, guidance, and decision-makers are expected to apply it with judgement to the circumstances of the site.
First-stage tests
The BRE guide contains simple geometric tests that act as a filter.
Distance and height. Where a new building is positioned at a distance of three or more times its height from the centre of a neighbouring window, a detailed assessment of loss of light to that window may generally not be necessary. This is a rule of thumb rather than a universal planning requirement.
The 45-degree test. Often used when assessing extensions and other proposals close to existing windows. A 45-degree line is drawn from the centre of the affected window in plan and/or elevation, depending on the assessment methodology. If the proposed development breaches the relevant 45-degree line, there may be a potential impact on light. It is not, by itself, proof of unacceptable loss of light.
The 25-degree test. Often used when assessing the effect of a proposed development on existing windows. A 25-degree line may be drawn from the centre of the lowest affected window towards the proposed development. If the development obstructs this line, further assessment of daylight may be warranted. Again, this is an assessment tool rather than an automatic test of unacceptable impact.
Garden and open space sunlight. For gardens and amenity spaces, the BRE guidance commonly uses a target that at least 50% of the assessed area should receive at least two hours of direct sunlight on 21 March. Where the area receiving two hours of sunlight falls below 50%, the change is assessed against the existing situation; the commonly used 0.8 ratio relates to the area receiving at least two hours of sunlight after development compared with the existing area.
A scheme that passes these tests is likely to be acceptable on daylight and sunlight grounds.
Failing them does not mean a scheme is unacceptable. It usually means more detailed technical assessment is needed.
Detailed assessment
Detailed assessments use measures such as Vertical Sky Component, No Sky Line and Annual Probable Sunlight Hours.
These are specialist calculations, usually prepared by a chartered surveyor or daylight and sunlight consultant using 3D modelling, and presented as a report with drawings and results tables.
The report will normally set out the results for each affected window and room, compare them with the BRE targets, and explain where a result falls short and why that may still be acceptable.
Why a shortfall is not always fatal
A scheme that falls below a BRE target can still be acceptable. Decision-makers will consider matters such as the existing context (a dense urban street will not have the same baseline as a rural edge), the importance of the room affected, whether the neighbouring window is itself unusually dependent on an open site, and the benefits of the scheme.
The case needs to be made, though, and it is much easier to make it with technical evidence than without.
Right to light is a separate matter
A neighbour may also raise a legal right to light. This is an easement, usually acquired by long use, that protects the light passing through a particular window over someone else's land.
If it is infringed, the remedy is a civil one: an injunction or damages, pursued through the courts.
That is a different question from the planning assessment.
Planning is concerned with land use in the public interest, and private rights are not normally material planning considerations in their own right.
If a neighbour has raised a right to light, it is sensible to get separate advice on that issue early
Development in a sensitive location?
Sites close to neighbouring homes, or in other sensitive locations tend to attract close scrutiny, and daylight and sunlight is often one of the first issues raised.
If you have a site like this and need help with the planning side, I can advise on the policy position, how much technical work is likely to be needed, and how to put the case together. Get in touch with me to talk through your site.
Andrew Ransome MRTPI - Email: andrew@andrewransome.co.uk
About me
Andrew Ransome is a Planning Director and a Chartered Member of the Royal Town Planning Institute (RTPI), with more than two decades of experience in town planning.
He specialises in delivering strategic planning solutions for complex developments across both rural and urban environments, helping clients navigate planning challenges and unlock development opportunities. Connect with Andrew on Linkedin.
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