If you are planning an extension or a new development anywhere from Basingstoke town centre to Tadley, Whitchurch or the strategic growth at Manydown, understanding the daylight requirements in Basingstoke and Deane will save you time and avoid costly delays. Basingstoke and Deane Borough Council sets out some of the most explicit daylight and sunlight guidance of any Hampshire authority, including named “rules of thumb” that officers use to judge whether a proposal harms a neighbour's light. This guide walks through the policy framework, the specific tests the council applies, and when a formal daylight and sunlight report is needed.
Who is the planning authority?
Basingstoke and Deane Borough Council is the local planning authority (LPA) for the borough. Hampshire County Council handles strategic functions such as minerals and waste, but it is the borough council that decides householder and residential planning applications and that adopts the relevant local policy and guidance. The documents below are therefore the ones that govern daylight on your site.
The adopted Local Plan 2011 to 2029
The development plan is the Basingstoke and Deane Local Plan 2011–2029, adopted on 26 May 2016, which sets the strategy and policies up to 2029 — including the large strategic allocation at Manydown to the west of Basingstoke. The council is preparing an update to the Local Plan, but the 2016 plan remains the adopted framework for decisions.
The key policy for light is Policy EM10 (Delivering High Quality Development). Policy EM10 permits development where it will, among other things, “provide a high quality of amenity for occupants of developments and neighbouring properties, having regard to such issues as overlooking, access to natural light, outlook and amenity space, in accordance with the Design and Sustainability SPD”. Access to natural light is therefore an explicit policy test, and the policy expressly directs applicants to the supporting SPD for the detail.
The Design and Sustainability SPD and its daylight rules
The detailed guidance sits in the council's Design and Sustainability Supplementary Planning Document (SPD), which supports Policy EM10 and is a material consideration in deciding applications. The SPD is notably specific about how daylight, sunlight and outlook are assessed, and it contains a dedicated “Natural Light and Outlook” section.
The SPD sets two clear starting points. It states that:
Dwellings must have sufficient daylight to allow the comfortable use of habitable rooms (living rooms, dining rooms, bedrooms), kitchens and patio areas in gardens immediately adjoining the building… All dwellings should receive some direct sunlight in at least one habitable room in all months of the year.
It then introduces two named “rules of thumb” that are widely used in the borough's decisions:
- The 25-degree rule: “there is normally the potential to achieve adequate levels of daylight and outlook when no facing building breaks a 25 degree angle from the horizontal from a point 2 metres above the floor level” (the normal height of windows), taking account of changes in ground level.
- The 45-degree rule: “there is normally the potential to achieve adequate levels of daylight and outlook when no part of a building cuts through a line radiating at 45 degrees from the centre of a window that lights a habitable room”. The SPD notes this takes account of the height of a proposed development, as two-storey schemes have greater potential impact.
Crucially for anyone planning works, the SPD states at paragraph 10.20: “If there is a potential adverse impact upon the levels of light enjoyed by properties, then planning applications may need to be accompanied by a daylight/sunlight assessment.” That is the trigger to look out for — where the 25-degree or 45-degree rule is breached, the council can require a formal daylight and sunlight assessment.
Residential amenity and extensions guidance
The SPD's residential amenity design principles reinforce these tests. Principle RA7 states: “New development must provide a suitable, pleasant outlook and level of natural light for both new and neighbouring dwellings.” For house extensions specifically, the SPD warns that “extensions to the south of the existing or neighbouring property are likely to cause overshadowing and loss of direct sunlight to important habitable rooms”, and principle E1 requires that detrimental impacts on neighbours — including overbearing impacts and blocking out natural light — must be prevented. The SPD also references the familiar 20-metre back-to-back separation distance used to protect privacy and outlook between facing dwellings.
From rules of thumb to BRE methodology
The SPD is candid that “there are no quantitative standards to be applied in every case” — the 25-degree and 45-degree rules are screening tools, not the final word. Where they indicate a potential problem, a quantitative assessment is needed, and the recognised methodology is the Building Research Establishment's BRE BR 209, “Site layout planning for daylight and sunlight: a guide to good practice” (2022 edition). BR 209 provides the numerical tests — Vertical Sky Component (VSC), daylight distribution / the no-sky line, and Annual Probable Sunlight Hours (APSH) for sunlight, plus overshadowing assessment of gardens and amenity areas. For the internal daylight of new dwellings, BS EN 17037 is the relevant standard. These are what a robust daylight and sunlight report submitted under Policy EM10 and the SPD should contain.
Local context worth noting
- Manydown strategic growth: The Local Plan allocates major housing growth at Manydown west of Basingstoke. Large layouts of this kind make daylight, sunlight and overshadowing between new homes and amenity spaces a central design issue from masterplanning onwards.
- A specific local trigger: Because Basingstoke and Deane names the 25-degree and 45-degree rules in its adopted SPD, officers and neighbours routinely apply them. A scheme that breaches either line near a habitable-room window should anticipate a request for a daylight and sunlight assessment under paragraph 10.20.
How Fortress Associates can help
Fortress Associates provides our daylight and sunlight report service to BRE BR 209 (2022), BS EN 17037 and the relevant Local Plan, producing the VSC, daylight distribution, APSH and overshadowing evidence that Basingstoke and Deane's Design and Sustainability SPD and Policy EM10 call for. We work nationwide with a 4–5 working day turnaround and no advance payment, and we also prepare Building Regulations drawings. If a 25-degree or 45-degree line has been breached, a clear technical assessment is usually the quickest way to address an officer's concern. Contact us to discuss your project. If you are working elsewhere in Hampshire, see our guide to daylight requirements in Rushmoor.
Sources & further reading
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