Daylight and sunlight assessment
A daylight and sunlight assessment measures how much natural light a new building or extension would take from neighbouring windows and gardens, and how much light the new rooms themselves would get. Councils ask for one when a scheme could affect neighbours, and it is often confused with a right to light survey, which answers a different question.
This guide covers the rules in England. See Wales, Scotland and Northern Ireland.
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Two different questions
Daylight and sunlight assessment
Tests how a scheme affects neighbouring windows and gardens, and the light in the new rooms, against published guidance. A council uses it to judge the effect on neighbours.
Right to light survey
Looks at whether a neighbour has a legal right to light through particular windows, and whether your building would infringe it. This is a private property right, separate from planning.
When a daylight and sunlight assessment is asked for
- The council’s validation list or pre-application advice says one is needed
- A new building or extension would be close to, or taller than, a neighbour’s habitable windows
- A scheme of flats or several homes where the new rooms need enough daylight themselves
- A neighbour has objected on loss of light and the planning officer wants it tested
What the consultant measures
Consultants usually follow the BRE guidance, Site layout planning for daylight and sunlight, which councils commonly refer to. It sets out tests for how much sky is visible from a window and how much of a room gets direct light, and for how much sunlight reaches windows and gardens. The guide gives targets, but they are guidance rather than law, and councils apply them with some flexibility, particularly in built-up areas.
Planning permission does not remove a right to light
A right to light is a legal right a neighbour can acquire over time. Getting planning permission does not override it, so a neighbour could still bring a claim even if the council approves the scheme. If a neighbour’s windows are close to your proposal, it is worth getting a rights of light opinion before design is fixed, not after construction starts.
In Wales, Scotland and Northern Ireland
This guide describes the rules in England. Building regulations are devolved, so here is how daylight and sunlight assessment works in the rest of the UK.
The BRE guidance is used by Welsh councils too, and planning is decided by your local planning authority. The law on rights of light is similar to England’s, but take advice for your case.
Scotland has its own planning system and its own law of servitudes, so the rules on rights to light differ from England’s. Councils may refer to the BRE guidance. Take local legal advice.
Planning is decided by your council. The law on rights to light differs in detail from England’s, so take legal advice for your case.
Common questions
Does my house extension need a daylight and sunlight assessment?
Most householder extensions do not. Councils often use simple rules of thumb for a small extension next to a neighbour’s window. Check your council’s validation list or ask in a pre-application enquiry.
What is the difference between this and a right to light survey?
A daylight and sunlight assessment is for planning and tests effects against guidance. A right to light survey is about a neighbour’s legal right. You might need either, both or neither, depending on the site.
What is a right to light?
It is a legal right, often acquired through long, uninterrupted use, to receive light through a particular window or opening. If a new building cuts that light by enough, the neighbour may be able to challenge it. Take advice from a rights of light specialist or solicitor.
Can a neighbour stop my extension with a right to light?
It is possible in some cases, whether or not you have planning permission. Many cases are settled by changing the design or agreeing compensation, which is why it is better to look at the risk early.
How much does an assessment cost?
It depends on the size of the scheme and the number of windows to test. Consultants set their own prices, so compare quotes and check what each includes.
Does the assessment cover my own rooms too?
It can. For new homes and flats, consultants also test whether the rooms in your own scheme get enough daylight. Ask for this to be included if you need it.
New to the jargon? See our glossary of terms, from air permeability to TrustMark.