Daylight requirements in Buckinghamshire are shaped by an unusual planning landscape. Since 1 April 2020, Buckinghamshire Council has been a single unitary authority and the local planning authority for the whole county, replacing the former district councils of Aylesbury Vale, Chiltern, South Bucks and Wycombe. Yet the planning policies those districts adopted remain in force. If you are extending a home, building new dwellings or developing a site anywhere from Aylesbury to Amersham, the daylight and sunlight standards that apply to your scheme depend on which part of the county it sits in.
This guide explains how daylight and sunlight are assessed in Buckinghamshire, which adopted plans and design guidance apply, and how a professional daylight and sunlight report prepared to the correct standards can support your planning application.
The multi-plan situation in Buckinghamshire
Buckinghamshire is one of the more complex authorities in England for planning policy, because the council inherited four separate development plans when it was formed. Until a single Buckinghamshire-wide local plan is adopted, the following adopted documents continue to apply, each to its respective area:
- Vale of Aylesbury Local Plan (VALP) 2013–2033 – adopted 15 September 2021, covering the former Aylesbury Vale area.
- Wycombe District Local Plan – adopted August 2019, covering the former Wycombe area, alongside the Delivery and Site Allocations Plan.
- Chiltern District plans – including the Chiltern Core Strategy (adopted 2012) and the saved Chiltern District Local Plan policies.
- South Bucks District plans – including the South Bucks Core Strategy (adopted February 2011) and saved South Bucks Local Plan policies.
The council is preparing a new, unified Buckinghamshire Local Plan that will eventually replace these legacy documents and allocate development across the county. Until that plan is adopted and its policies carry full weight, applicants must identify the correct legacy plan for their site and apply the relevant policies. Getting this right at the outset matters: a daylight and sunlight assessment must be framed against the specific policy that the case officer will use to determine the application.
Local plan policies on amenity and design
Across all four legacy plans, the protection of residential amenity – including daylight, sunlight, outlook and privacy – is a recurring material consideration. Two of the more recently adopted plans set out the design and amenity tests most directly:
- In the former Aylesbury Vale area, VALP Policy BE1 (Design of new development) requires development to be of a high standard of design that responds to its context, with Policy BE2 dealing with design of public realm and related matters. Together these policies require schemes to safeguard the amenity of existing and future occupiers.
- In the former Wycombe area, Policy DM35 (Placemaking and design quality) is the principal design policy, requiring development to create high-quality places and protect the amenity of neighbours. The plan also sets amenity-space expectations, including that private gardens should generally have a minimum depth of 12 metres and be free from excessive shade.
The Chiltern and South Bucks plans similarly treat amenity as a material consideration, reflecting long-standing national guidance that the loss of light to neighbouring habitable rooms and gardens can be a legitimate reason to refuse or amend a scheme. Because the Chiltern and South Bucks areas include large parts of the Chilterns National Landscape (formerly the Chilterns Area of Outstanding Natural Beauty), design and amenity scrutiny in these areas can be particularly close.
Daylight and sunlight guidance in Buckinghamshire
Buckinghamshire Council’s adopted supplementary guidance gives practical detail on how amenity is protected. The Aylesbury Vale Area Design Supplementary Planning Document sets out design principles requiring homes to receive adequate daylight and sunlight and to avoid overshadowing, and confirms that extensions should not cause significant harm to neighbours’ amenity in terms of privacy, outlook, daylight and sunlight.
That guidance applies the well-known 45-degree rule: two-storey extensions should not encroach beyond a 45-degree line taken from the edge of the nearest ground or first-floor window of a habitable room of a neighbouring property. The 45-degree line is a quick screening tool intended to prevent undue loss of daylight or sunlight and excessive overshadowing of gardens. It does not replace a full technical assessment – where a scheme is more sensitive, or where the 45-degree test is failed, a detailed numerical analysis is expected.
For that detailed analysis, the council – in common with authorities across the UK – looks to the Building Research Establishment’s guidance. The relevant document is BRE BR 209, Site Layout Planning for Daylight and Sunlight: A Guide to Good Practice (2022 edition), supported by the daylight provision recommendations of BS EN 17037. These technical benchmarks are applied through the local plan amenity policies and through the National Planning Policy Framework, which requires good design and a high standard of amenity for existing and future users.
What a daylight and sunlight report should cover
Where Buckinghamshire Council requests a daylight and sunlight assessment to support an application, it expects the report to address:
- the existing and expected levels of daylight, sunlight and overshadowing affecting neighbouring properties;
- the daylight and sunlight that the proposed new units will themselves receive; and
- any measures proposed to mitigate adverse impacts.
A BR 209-compliant report typically uses the Vertical Sky Component (VSC) and No Sky Line / Daylight Distribution tests for daylight, the Annual Probable Sunlight Hours (APSH) test for sunlight to neighbouring windows, and overshadowing analysis for amenity areas. For the proposed dwellings, daylight provision is assessed against the targets in BS EN 17037 and BR 209.
Local specifics worth knowing
- Large parts of the county lie within the Chilterns National Landscape, where landscape character and design quality attract close attention – schemes here should expect detailed amenity and design scrutiny.
- Conservation areas and listed buildings are common across historic towns such as Amersham, Beaconsfield, Marlow and Aylesbury’s old town, where extensions and infill must balance daylight gains against heritage and amenity constraints.
- Validation requirements vary by site: the council’s additional supporting documents guidance confirms that a daylight and sunlight assessment may be required where a proposal could materially affect light to neighbours or where new accommodation could be poorly lit.
How Fortress Associates can help
Fortress Associates prepares our daylight and sunlight report service to BRE BR 209 (2022) and BS EN 17037, framed against the correct Buckinghamshire legacy plan and its amenity policies for your site. We work nationwide with a 4–5 working day turnaround and no advance payment required. We also provide Building Regulations drawings to Approved Documents A–S. To discuss your scheme, please get in touch or see our full range of services. You may also find our companion guide on daylight requirements in Central Bedfordshire useful if your project spans the wider region.
Sources & further reading
Need help with a UK planning project?
Fixed-fee daylight reports and Building Regulations drawings — delivered in 4–5 working days. No advance payment.
Request a free quote