Daylight Requirements in Caerphilly

Caerphilly Castle with its moat and stone towers, Caerphilly County Borough

If you are planning an extension, a new home or a residential development anywhere across Caerffili, understanding the daylight requirements in Caerphilly will save time and reduce the risk of objections. From the principal towns of Caerphilly, Bargoed, Blackwood, Ystrad Mynach and Risca/Pontymister to the valley settlements in between, the impact of a proposal on light and privacy to neighbouring homes is one of the issues planning officers scrutinise most closely. This guide sets out the adopted policy framework, the council's amenity standards, and how a professional daylight and sunlight report supports your application.

Daylight requirements in Caerphilly: the planning framework

Planning applications in Caerphilly are determined against the adopted development plan together with national policy. The adopted plan is the Caerphilly County Borough Local Development Plan up to 2021, adopted in November 2010. A replacement plan is being progressed, but until that emerging plan is adopted the 2010 LDP remains the statutory development plan against which proposals are assessed; applicants should always check the council's website for the latest position before submitting.

The adopted LDP is read alongside the Welsh national framework: Planning Policy Wales (Edition 12, 2024), Future Wales: the National Plan 2040, and the relevant Technical Advice Notes, notably TAN 12: Design. Planning Policy Wales puts placemaking and good design at the centre of decision-making, and the protection of amenity, including reasonable access to daylight and sunlight, is part of that approach.

Policy CW2: Amenity

The key countywide development management policy is Policy CW2 (Amenity). It requires, among other things, that development proposals demonstrate:

that there is no unacceptable impact on the amenity of adjacent properties or land; and
that the proposal would not result in over-development of the site and/or its surroundings.

Loss of daylight or sunlight, overshadowing and unacceptable overlooking are all matters that engage CW2: a scheme that materially harms light to a habitable room, or that crowds a plot beyond what its context can absorb, can be resisted under this policy. CW2 sits alongside the wider suite of countywide policies (such as the design and transport considerations in Policy CW3) that together shape how development is judged.

SPG LDP7: Householder Developments

For householder schemes the most directly useful document is the adopted Supplementary Planning Guidance LDP7: Householder Developments, supported by LDP6: Building Better Places to Live for residential design more broadly. LDP7 translates CW2 into practical amenity tests, including:

The 45-degree test: overshadowing and overbearing impact are unlikely to be unacceptable where an extension does not breach a line taken at 45 degrees from the centre of the nearest ground-floor window of a principal room in an adjoining property.
Extension length guidance: as a general rule single-storey extensions on a common boundary near a neighbour's principal-room window should be no longer than around 4 metres, and two-storey extensions on the boundary no longer than around 2 metres at first floor, subject to orientation and context.
Privacy and overlooking: facing habitable room windows in a back-to-back situation should generally be at least 21 metres apart, with rear first-floor windows kept a suitable distance from boundaries to avoid direct overlooking of neighbouring gardens.
Sloping sites: the guidance specifically flags that on sloping plots extra care is needed, as even ground-floor extensions can overlook lower properties, a common situation in the Caerphilly valleys.

These are guidance tests and the council retains discretion, but they frame most householder decisions across the County Borough.

BRE BR 209 and BS EN 17037: the technical methodology

For larger or more sensitive proposals, the council and applicants rely on the recognised technical standards: the BRE guide BR 209, Site Layout Planning for Daylight and Sunlight: A Guide to Good Practice (2022 edition), together with BS EN 17037 (Daylight in Buildings). A BR 209 assessment goes beyond simple angular rules and quantifies impact using:

Vertical Sky Component (VSC) and the daylight distribution (no-sky line) test for daylight to existing windows;
Annual Probable Sunlight Hours (APSH), including the winter component, for sunlight to existing homes;
Overshadowing of gardens and amenity spaces, commonly tested against the two-hour sunlight-on-21-March benchmark.

This methodology gives planning officers, and where necessary the Planning and Environment Decisions Wales (PEDW) inspectorate, clear and defensible evidence on which to base a decision.

Local factors that affect daylight assessments in Caerphilly

Steep valley topography. Much of the County Borough is characterised by steeply terraced valley settlements; where homes are stacked up hillsides, orientation and level differences strongly affect both sunlight and overlooking, which is why LDP7 singles out sloping sites for extra scrutiny.
Dense terraced townscapes. The principal towns and older terraces have tight back-to-back layouts and small rear gardens, so the 21-metre separation and 45-degree tests are frequently the deciding factors for rear extensions and dormers.
Constrained urban infill. With limited greenfield release in the adopted plan, much new housing comes forward as infill within established streets, where careful daylight, sunlight and overshadowing analysis is essential to demonstrate compliance with CW2.

How Fortress Associates can help

Fortress Associates provides our daylight and sunlight report service for homeowners, architects and developers across Caerphilly and throughout Wales. We prepare assessments to BRE BR 209 (2022) and BS EN 17037, referenced to Policy CW2 and the council's Householder SPG, giving your application clear supporting evidence. We work to a 4-5 working day turnaround and ask for no advance payment. See our services or contact us to discuss your project.

Sources & further reading

daylightsunlightCaerphillyBRE BR 209planning WalesLocal Development PlanPolicy CW2daylight assessment

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