You have your drawings ready for an extension or a new build. Then the council – or a neighbour – raises “loss of light”, and suddenly you are being asked for a daylight and sunlight report. What is it, do you really need one, and how does it help you get approved? Here it is in plain English.
What a daylight and sunlight report is
It is a short technical report that measures how much natural light your project would take away from the buildings around it. It looks at your neighbours’ windows and gardens, works out how much daylight and sunshine they get now and how much they would get after your project is built, and compares the results against national guidance. The council gets numbers instead of opinions – and that is exactly why it works. Without a report, a “you will block my light” objection is one person’s word against another’s. With one, there is a clear answer either way.
Who sets the rules
The rulebook is guidance from the Building Research Establishment – the BRE guide, last updated in 2022. Almost every UK council uses it, and appeal inspectors lean on it heavily. Pass the BRE tests and a loss-of-light objection rarely succeeds.
The three tests, made simple
1. The 45-degree rule. Draw a line at 45 degrees from your neighbour’s nearest window. If your extension crosses it, the council will want a closer look. Most officers use this as the quick first check.
2. How much sky the window can still see. This is the Vertical Sky Component, or VSC. A window that can still “see” a good slice of sky (27% is the benchmark) stays well lit. And the most useful number in the whole guide: even below that benchmark, a loss only counts as noticeable if the window keeps less than 80% of the light it had before. Keep every affected window above 80% of its old light and you are usually in safe territory.
3. Sunshine and gardens. For windows facing south or close to it, the guide checks sunlight hours across the year and in winter. Gardens have their own test: at least half the garden should still get two hours of direct sun on 21 March. Overshadow most of a neighbour’s garden and expect that objection to stick.
When councils ask for one
Not every project needs a report. A modest single-storey extension with generous gaps to the neighbours usually does not. A report is commonly required when your project comes close to a shared boundary; when you build two storeys near a neighbour’s windows; for flats or anything taller than the buildings next door; on tight urban streets; when a neighbour objects about light; or simply because the council’s validation list requires one for your type of scheme. If in doubt, check the validation requirements on your council’s website before you submit.
How it helps you win approval
A daylight report is not a hurdle – used early, it is evidence on your side. It deals with objections: if a neighbour says your extension will darken their kitchen and the report shows their window keeps 85% of its light, the objection loses its force. It catches problems while they are cheap: if one window fails a test, a small design change – pulling back a metre, lowering a roof slope – often fixes it before you apply. And it speeds the decision, because complete applications move through validation faster.
Cost and timing
For a typical householder scheme, a daylight and sunlight report is one of the cheaper documents in your application – usually a few hundred pounds, not thousands. Assessors work from your existing and proposed drawings, so a site visit is rarely needed. Fixed-fee specialists such as Fortress Associates (details at https://clockfortress.com/fortress-associates/) deliver BRE-based reports in around 4 to 5 working days from your drawings. One tip: have both sets of drawings ready before asking for quotes – every assessor needs them, and sending them upfront gets you an accurate price straight away.
Three details that surprise people
Dense areas get flexibility. The 2022 edition of the BRE guide openly says its numbers should be applied flexibly in historic and dense urban settings, where meeting suburban daylight levels is unrealistic. A good report uses that flexibility in your favour rather than leaving it on the table.
It can protect your own scheme too. The same tests are used to check whether a neighbouring site could later be developed in a way that harms your light – useful knowledge if you are buying a plot or a flat with a gap site next door.
You can screen your design yourself first. The 45-degree rule and the 80% rule are simple enough to sketch-check on your own drawings before you spend anything. If the design clears them comfortably, you may never need the full report; if it is marginal, you know to get one early.
Daylight reports and “right to light” are different things
“Right to light” is a separate legal matter between property owners, decided under property law – not planning. Winning planning permission does not remove a neighbour’s legal rights, and vice versa. For most home projects the planning tests are what matter; legal right-to-light disputes are rare and mainly affect larger city schemes.
The bottom line
If your project sits close to neighbours, assume light will come up. Check the 45-degree rule on your own drawings, and if it looks tight, get the daylight and sunlight report early – before an objection lands, not after. It is fast, it is one of the cheapest reports you will buy, and it turns the weakest point of your application into the evidence that carries it. In planning, the applicant with the numbers usually wins.
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