Whether you are extending a home in Old Stevenage, building out a plot in one of the neighbourhoods, or bringing forward a larger scheme in the regenerating town centre, understanding the daylight requirements in Stevenage matters from the outset. Stevenage Borough Council is the local planning authority (LPA) that decides planning applications across the town; Hertfordshire County Council is not the LPA for these decisions. This guide explains the local policy framework, the council's design guidance on daylight and sunlight, and how a professional report supports a strong application.
The planning framework: daylight requirements in Stevenage
The statutory development plan is the Stevenage Borough Local Plan 2011-2031, adopted on 22 May 2019. The plan provides for around 7,600 new homes over its period, alongside jobs, infrastructure and major town-centre renewal. Two policies are central to daylight and sunlight:
- Strategic Policy SP8 (Good Design) sets the overarching expectation that development achieves a high quality of design that responds to its context and creates good living conditions.
- Detailed Policy GD1 (High Quality Design) requires development to respect and make a positive contribution to its surroundings and to avoid an adverse impact on the amenity of future occupiers, neighbouring uses or the surrounding area. Loss of daylight, sunlight, privacy and outlook are assessed under GD1.
These policies are read alongside the National Planning Policy Framework (NPPF), which requires a high standard of amenity for existing and future users of land and buildings.
The Stevenage Design Guide SPD
Stevenage gives detailed practical effect to its design policies through the Stevenage Design Guide Supplementary Planning Document (SPD), adopted in January 2023. The SPD contains a dedicated section on Sunlight, daylight and orientation that sets out exactly how the council expects daylight and sunlight to be addressed.
The SPD states that new developments should be designed to ensure a satisfactory level of sunlight and daylight is provided for the occupants of both existing and proposed dwellings (paragraph H.19). Where there is doubt that adequate light will be achieved, indicators are used to assess the light reaching a window (H.20).
Crucially, the SPD names the technical benchmark directly (H.21):
"The Building Research Establishment (BRE) guidelines 'Site Layout Planning for Daylight and Sunlight: A Guide to Good Practice'... will be used. It provides guidance on avoiding unacceptable impacts and sets out non-mandatory targets... The guidance contained in the revised advice has been updated to reflect the changes in the British Standard Daylight in buildings, BS EN 17037."
The SPD confirms that, for neighbouring properties, Vertical Sky Component (VSC) and Daylight Distribution (DD) remain the daylight tests, and Annual Probable Sunlight Hours (APSH) remains the sunlight test.
The 25-degree test and when a full assessment is needed
For existing buildings, the SPD applies the BRE 25-degree test as a first check (paragraphs H.21-H.22). From a point 2 metres above ground level at the centre of a neighbour's window, a line is drawn at 25 degrees to the horizontal; if the proposed development cuts that line, it is likely to interfere with the diffuse skylight the existing building enjoys. In that case, the SPD states it will be "necessary to undertake a detailed sunlight and daylight assessment."
The SPD also notes that on sloping sites overshadowing is more of a problem and greater spacing is required to maintain access to daylight - a relevant point given Stevenage's varied topography. For private outdoor space, the guide expects rear gardens and communal open spaces to enjoy a reasonable amount of sunlight, with new houses provided a garden of at least 50 square metres and a depth of at least 10 metres.
How daylight and sunlight are technically assessed
The current edition of the BRE guidance is BRE BR 209: Site Layout Planning for Daylight and Sunlight - A Guide to Good Practice (2022), read with BS EN 17037. A typical Stevenage assessment covers:
- Vertical Sky Component (VSC) - the skylight reaching a neighbour's window, benchmarked at 27%.
- Daylight Distribution (no-sky line) - how far daylight reaches into existing rooms.
- Annual Probable Sunlight Hours (APSH) - for windows with a southerly aspect.
- Overshadowing of gardens and amenity space - testing sunlight on 21 March.
This is precisely the analysis the council expects once the 25-degree test is breached.
Local context: development pressures in Stevenage
Stevenage has a distinctive planning context:
- The UK's first New Town - designated in 1946, Stevenage was built to a planned layout with generous spacing and open landscaping. Infill and intensification within this pattern need careful daylight and sunlight handling to respect the original design quality.
- Town-centre regeneration - the Local Plan supports major renewal of Stevenage town centre with taller, denser mixed-use buildings, where daylight, sunlight and overshadowing are key considerations for both new homes and surrounding properties.
- Strategic housing growth - sites such as the West of Stevenage development bring forward large numbers of new homes, where the layout-stage daylight and sunlight design tested by the SPD is especially important.
When you may need a daylight and sunlight report
You should commission a report where your proposal could reduce a neighbour's light - for instance a two-storey or rear extension near a boundary, a backland or infill dwelling, a flatted or town-centre scheme, or any case where the 25-degree test is breached. The report demonstrates compliance with Policies SP8 and GD1 and meets the Design Guide SPD's expectation of a detailed assessment.
How Fortress Associates can help
Fortress Associates provides our daylight and sunlight report service for projects in Stevenage and across the UK. Our reports follow BRE BR 209 (2022) and BS EN 17037, giving officers the evidence required by the Stevenage Design Guide SPD and Policies SP8 and GD1. We offer a 4-5 working day turnaround with no advance payment. Explore our services or contact us to discuss your project.
Sources & further reading
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