Objective figures when light is holding up your extension
A daylight and sunlight assessment measured against the BRE guidance London councils actually use, so a planning officer has numbers to weigh instead of two neighbours disagreeing.
Get a fee and timescaleNo payment on this page. You get a fixed fee first, and an honest answer if this is not what you need.
Why the price is on the page
No daylight and sunlight consultancy publishes a fee at any tier, so working out whether this is a £500 problem or a £5,000 one currently takes three phone calls. These are honest anchors. If your case is bigger than a small scheme, we will tell you rather than stretch the fee to fit.
What the report contains
- Every affected neighbouring window, located from drawings and a site visit
- The 45-degree and 25-degree tests against BR209 (2022)
- Vertical sky component and sunlight hours where the case needs it
- Method, assumptions, results and diagrams
- A plain-English conclusion, signed by the practice
- If it fails: the design changes that would fix it
Formatted to submit with a planning application as supporting evidence.
When this is the right thing to commission
Most extensions never need one. Four situations are where it earns its fee:
A neighbour has objected on light.
An objection stated as a feeling is hard for an officer to weigh. The same objection answered with BRE figures becomes a planning judgement rather than a dispute.
The council has asked for evidence.
Some London boroughs request a daylight and sunlight study for two-storey or deep rear extensions close to a boundary. Supplying it late costs you weeks on the clock.
You are about to commit to a design.
Finding out at the objection stage that a scheme fails the guidance is expensive. A setback or a lower roof, decided early, is not.
A small scheme where light is the main risk.
Two to five units on a tight London plot, where the surrounding windows are the constraint that shapes the massing.
Fees
Both are fixed fees, confirmed in writing once we have seen the drawings.
Householder
One extension, assessed against one or two neighbouring properties. The usual rear or side extension case, and the one most objections concern.
Small scheme
Two to five units, or a single building affecting several neighbours, where massing options need testing before you commit to a design.
Where a case needs a chartered right to light surveyor instead, we will say so before taking any money.
The service, in full
- Price
- From £1,450 for a householder assessment, from £2,450 for a small scheme. Fixed and confirmed in writing once we have seen the drawings, because scope drives the work.
- Turnaround
- 5 working days from receiving drawings. Say so if you are against a deadline and we will tell you honestly whether we can meet it.
- Method
- BRE Site Layout Planning for Daylight and Sunlight, BR209 (2022): the 45-degree and 25-degree tests, and where the case calls for it vertical sky component and annual probable sunlight hours. The same guidance your planning officer applies.
- Scope
- Every neighbouring habitable window your proposal could affect, located from the drawings and a site inspection rather than assumed.
- Format
- A written report with method, assumptions, results, diagrams and a plain-English conclusion, signed by the practice and formatted to submit as supporting evidence.
- If it fails
- The setbacks, height reductions or roof changes that would bring the scheme back within the guidance, with the effect each one has on your internal area.
- What we need
- Existing and proposed drawings with dimensions, the address, and anything the council or a neighbour has put in writing about light. No drawings yet? We can quote for producing them first.
- Payment
- Nothing is taken on this page. You get a fixed fee and a timescale first, and an honest answer if this is not the right thing to commission.
- What it is not
- Not a formal Right to Light assessment under the Prescription Act 1832, not a guarantee of planning permission, and not legal advice.
What this is not
- Not a formal Right to Light assessment under the Prescription Act 1832. If a neighbour has an established right and is threatening an injunction, that is a chartered right to light surveyor’s work, and we will refer you.
- Not a guarantee of planning permission. It is evidence for the decision maker, and the figures can go against you.
- Not a legal opinion, and not a substitute for advice from a solicitor on rights, releases or insurance.
- Not an internal daylight assessment for a large residential development, which is a different and larger piece of modelling.
Mayfair Studio is a London planning and design practice. We are not ARB registered and do not describe ourselves as architects.
Not sure whether light is actually a problem yet?
Start with the free risk check in our right to light article. It walks through the 45-degree rule and the Prescription Act in five questions and tells you whether this is worth spending money on.
Take the free right to light risk checkGet a fee and timescale
Tell us what is proposed and what has happened so far. You get a fixed fee, a timescale, and an honest answer if this is not the right thing to commission. No payment is taken on this page.
Common questions
What is a daylight and sunlight assessment?
A technical study of how much daylight and sunlight a proposed building removes from neighbouring windows, and how much the proposal itself receives. It is assessed against the BRE guidance, Site Layout Planning for Daylight and Sunlight (BR209, 2022), which is the document London planning officers work from. The output is a set of numbers and diagrams that a planning officer or a committee can weigh, rather than an opinion.
Do I need one for a householder extension?
Usually only when light is a live issue. The common triggers are a two-storey or deep rear extension close to a boundary, a neighbour who has objected on light, or a planning officer asking for evidence. For a modest single-storey extension that stays within the 45-degree line, the free risk check on our article is normally enough.
Is this the same as a right to light assessment?
No, and the difference matters. Daylight and sunlight is a PLANNING test, assessed against BRE guidance, and it is what a council considers when deciding an application. Right to light is a PROPERTY LAW matter under the Prescription Act 1832, tested by the 50/50 rule and capable of ending in an injunction. We produce the planning assessment. Where the issue is legal, an established right and the risk of an injunction, we refer you to a chartered right to light surveyor.
Why do you publish a price when nobody else does?
Because quote-on-request wastes your time when you are trying to work out whether this is a £500 problem or a £5,000 one. The tiers are honest anchors. If your case is genuinely bigger than a small scheme we will say so rather than stretch the fee to fit.
What do you need from me?
Existing and proposed drawings (plans, elevations and a section) with dimensions, the property address, and anything the council or a neighbour has already put in writing about light. If drawings do not exist yet, we can quote for producing measured drawings first.
Can it guarantee my application is approved?
No. Nothing can. A daylight and sunlight assessment gives the decision maker objective figures where the alternative is an argument between neighbours. Where the figures are unfavourable, that is worth knowing before you submit, because a setback or a reduced height often moves a scheme back within the guidance.