For anyone planning a house extension, new home or larger residential scheme in Staines-upon-Thames, Sunbury-on-Thames, Shepperton, Ashford or Stanwell, understanding the daylight requirements in Spelthorne is an important early step. Spelthorne Borough Council is the local planning authority (LPA) for this part of Surrey — not Surrey County Council — and it has unusually clear, locally specific guidance on daylight and sunlight. This guide explains the policy framework, the technical tests the council applies, and how a professional daylight and sunlight report can support your application.
The planning framework for daylight in Spelthorne
Development in the borough is now guided by the Spelthorne Local Plan 2024–2039/40, which was adopted by the council on 17 March 2026. This new plan replaced the long-standing 2009 development plan, comprising the Core Strategy and Policies Development Plan Document and the Allocations Development Plan Document, both adopted in 2009. When you apply for planning permission in Spelthorne today, your proposal is assessed against this adopted plan.
The central design policy is Policy PS2 – Designing Places and Spaces. It requires a high standard of design and layout and, under its “Impact on Neighbours” provisions, states that proposals should:
"achieve a satisfactory relationship to adjoining properties avoiding adverse and un-neighbourly impacts in terms of loss of privacy, daylight or sunlight, or overbearing effect due to bulk and proximity or outlook."
This policy carried forward and updated the approach of the former Core Strategy Policy EN1 (Design of New Development), which it supersedes. Place-based policies in the plan, including Policy SP1 (Staines-upon-Thames) and the policy for Ashford, Shepperton and Sunbury Cross, set the spatial context in which design and amenity are judged. Taken together, these policies give the council a firm basis to refuse schemes that would cause an unacceptable loss of daylight or sunlight, or that would feel overbearing to neighbours.
Spelthorne's daylight and sunlight guidance: the 25° and 45° tests
Spelthorne is more prescriptive than many authorities. Alongside the Local Plan, the council adopted a Spelthorne Design Code Supplementary Planning Document (SPD) at the same March 2026 meeting, providing detailed guidance to support the design policies. The council also maintains its long-standing “Design of Residential Extensions and New Residential Development” SPD, which sets out practical daylight and sunlight tests drawn directly from BRE guidance. It expressly refers applicants to the Building Research Establishment report Site Layout Planning for Daylight and Sunlight and a British Standard on lighting for buildings, and it expects applicants to demonstrate on their plans that the following are met:
- The 25° guide – to protect a significant view of the sky, no extension or new dwelling should break a 25° line measured from the centre of the main window of a habitable room at a point 2 metres above ground level. The SPD notes this is usually achieved when the recommended separation distances are followed, but greater separation may be needed where there are level differences or taller buildings.
- The 45° guide for side windows – where the main window of a habitable room is on the side of a property, an extension or new dwelling must not break a 45° vertical line drawn from the face of that side window, measured 2 metres above ground level.
The SPD also addresses sunlight, warning that significant loss is most likely where an extension or new dwelling is to the south of an existing property, and it sets separation distances and minimum retained garden depths (for example, around 15 metres in many situations) to protect privacy and amenity. Habitable rooms covered include lounges, dining rooms, kitchens, breakfast rooms, studies and bedrooms.
How this relates to the national methodology
Spelthorne's 25° and 45° guides are simplified design rules based on the wider BRE methodology. For larger or more sensitive schemes, the council and its neighbours will often want the fuller technical analysis set out in:
- BRE BR 209 (2022) – the current edition of Site Layout Planning for Daylight and Sunlight: A Guide to Good Practice, covering the Vertical Sky Component and No Sky Line daylight tests, Annual and Winter Probable Sunlight Hours, and overshadowing of amenity space.
- BS EN 17037 (Daylight in Buildings) – used to demonstrate that new dwellings themselves achieve adequate daylight.
- The NPPF – which is applied through Policy PS2 and asks for well-designed places and good living conditions.
When Spelthorne requires a daylight and sunlight assessment
Spelthorne's local validation requirements include a dedicated daylight and sunlight assessment. Where a proposal — such as a deep two-storey rear extension, a side extension close to a neighbour's window, a backland dwelling, or a flatted scheme — is likely to affect the daylight or sunlight reaching adjoining properties and their gardens, the council expects a daylight and sunlight assessment to be submitted. Demonstrating compliance with the 25° and 45° guides on your drawings, supported where necessary by a full BRE BR 209 report, is the most direct way to satisfy this requirement and avoid delay or invalidation.
Local context that shapes daylight assessments
- Suburban density and back-land pressure. Much of Spelthorne, from Ashford to Sunbury, is closely-built suburban housing where two-storey extensions and infill plots routinely raise daylight, overshadowing and privacy questions between neighbours.
- Green Belt and the River Thames. A large proportion of the borough is Green Belt, and the Thames frontage at Staines, Sunbury and Shepperton adds further constraints on scale and massing — factors that interact with how a building is oriented and how it overshadows surrounding land.
- Heathrow fringe. The borough sits on the edge of Heathrow Airport, and pressure for higher-density development near Staines town centre makes careful daylight and sunlight design especially important.
How Fortress Associates can help
Fortress Associates provides our daylight and sunlight report service for householders, designers and developers across Spelthorne and the rest of the UK. Our reports are prepared to BRE BR 209 (2022) and BS EN 17037, and demonstrate compliance with Spelthorne's 25° and 45° guides and Policy PS2. We offer a 4–5 working day turnaround with no advance payment, and can also produce Building Regulations drawings for your project. Contact us to discuss your site in Staines-upon-Thames, Sunbury, Shepperton or elsewhere in the borough.
Practical tips before you apply
- Test your design against the 25° guide for front and rear windows and the 45° guide for side windows early, before fixing the height and depth of an extension.
- Check whether your plot lies in the Green Belt or close to the River Thames, as this affects acceptable scale and massing.
- For larger or sensitive schemes, commission a full BRE BR 209 assessment to support the simplified guides on your drawings.
- If your project spans neighbouring authorities, see our companion guides on daylight requirements in Mid Suffolk and daylight requirements in West Suffolk.
Sources & further reading
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