Daylight requirements in Horsham are an increasingly important consideration for anyone proposing a new dwelling, an extension or a larger residential scheme in this part of West Sussex. Horsham District is a predominantly rural area centred on its historic market town, with a substantial proportion of land sitting close to the South Downs National Park boundary and within sensitive village settings. As pressure for new homes increases and plots become tighter, planning officers and neighbours alike pay close attention to how a proposal affects the daylight and sunlight reaching surrounding properties. This article explains how those requirements are framed locally and what an applicant should expect.
The local planning framework in Horsham
The local planning authority (LPA) for most of the area is Horsham District Council. It is worth being clear that West Sussex County Council is not the LPA for these proposals, and that land within the South Downs National Park is dealt with separately by the National Park Authority. For development across the rest of the district, the relevant adopted plan is the Horsham District Planning Framework (HDPF), adopted in November 2015.
The HDPF contains the policies that planning officers use to judge whether a scheme protects the amenity of existing and future residents, including the daylight and sunlight they receive. The two policies most often cited are:
- Policy 32 (Strategic Policy: The Quality of New Development), which requires development to be of a high standard of design and layout, taking account of scale, density, height, massing, siting, orientation and the space between buildings.
- Policy 33 (Development Principles), which requires proposals to provide or retain a good standard of amenity for existing and future occupiers, and to be designed to avoid unacceptable harm to neighbouring amenity — for example through overlooking, dominance or overshadowing.
In addition, where an increase in building height could significantly reduce the daylight or sunlight enjoyed by adjoining properties, gardens or amenity space, the council expects this impact to be addressed. The reference to overshadowing within Policy 33 is the hook on which most daylight and sunlight objections in Horsham hang, so it pays to demonstrate compliance with objective, recognised standards.
The emerging Local Plan
Horsham is also progressing a new Local Plan covering the period 2023–2040. The Regulation 19 version was approved in December 2023 and the plan was submitted for examination in July 2024; the examination has since been re-opened, with the Inspector indicating that development management policies will need updating in line with the Government's revised National Planning Policy Framework. Until that plan is adopted, however, the HDPF (2015) remains the development plan against which applications are determined. Applicants should keep an eye on the emerging policies but rely on the adopted framework today.
Is there a Horsham daylight and sunlight SPD?
Horsham District Council does not publish a dedicated Supplementary Planning Document setting numerical daylight and sunlight targets. Instead, the council's guidance on planning permission for home extensions sets out qualitative expectations — for example that a two-storey or first-floor rear extension on a detached house should not protrude beyond a 45-degree line drawn in the horizontal plane from the centre point of a habitable-room window of an adjoining property, and that extensions should be sympathetic in scale rather than overpowering.
Because there is no local numerical standard, the established national benchmarks fill the gap and are applied through the amenity policies of the HDPF. In practice this means:
- BRE BR 209 (2022) — the Building Research Establishment guide Site Layout Planning for Daylight and Sunlight, which provides the vertical sky component (VSC), no-sky-line (daylight distribution), annual probable sunlight hours (APSH) and overshadowing tests used by officers and consultants.
- BS EN 17037 — the British/European standard Daylight in Buildings, increasingly referenced for the daylight provision within new dwellings themselves.
- The National Planning Policy Framework (NPPF), which asks decision-makers to secure a high standard of amenity for existing and future users while avoiding an unjustified, blanket refusal of efficient land use.
The council's validation requirements identify the supporting information needed to register an application, with the level of detail depending on the size, type and sensitivity of the proposal. For schemes where height or massing could materially affect neighbouring light — a back-land plot beside two-storey homes, or a taller building near the historic Carfax in Horsham town centre, for instance — a daylight and sunlight assessment prepared to BRE BR 209 is a sensible and often expected submission.
What daylight requirements in Horsham mean in practice
Several characteristics of the district shape how these assessments play out:
- A compact historic core. Horsham town, focused on the Carfax and surrounding conservation areas, has tightly grouped buildings where even modest changes in height can affect a neighbour's light. Heritage and amenity considerations frequently combine.
- A largely rural district. Outside the main town, villages such as Billingshurst, Storrington, Pulborough and Henfield have lower-density layouts where overshadowing of gardens and the relationship between dwellings are key amenity tests.
- South Downs National Park sensitivity. The southern part of the district adjoins the National Park, raising design and landscape expectations even where a site is just outside the Park boundary.
A well-prepared assessment will measure the existing daylight and sunlight to neighbouring windows and amenity areas, model the proposed development, and compare the results against the BRE BR 209 numerical guidelines. Where a proposal meets those targets, it provides robust evidence that the scheme complies with HDPF Policies 32 and 33. Where targets are not fully met, the report can explain the context, the magnitude of any change and any mitigation — information that helps officers reach a balanced, evidence-led decision rather than a precautionary refusal.
Common triggers for an assessment
- Two-storey or first-floor rear and side extensions close to a boundary.
- New dwellings on infill or back-land plots surrounded by existing homes.
- Taller apartment or mixed-use schemes in or near the town centre.
- Proposals where a neighbour has already raised concerns about loss of light.
How Fortress Associates can help
Fortress Associates prepares our daylight and sunlight report service to BRE BR 209 (2022) and BS EN 17037, tailored to the policy context of the Horsham District Planning Framework. We work nationwide with a typical turnaround of four to five working days and ask for no advance payment. Visit our services page or get in touch via our contact page to discuss your site. For neighbouring schemes in nearby authorities, see our companion guide to daylight requirements in Mid Sussex.
Sources & further reading
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