Daylight requirements in Rhondda Cynon Taf are shaped by one defining feature: the steep-sided valleys. From the terraced streets that climb the hillsides above Pontypridd, Aberdare and the Rhondda Fawr and Rhondda Fach valleys, much of the county borough's housing sits on sloping ground where homes are built close together and where overshadowing is a genuine, everyday planning concern. If you are extending a property, building in an infill plot, or proposing flats, the council will expect you to show that your scheme protects the daylight and sunlight enjoyed by neighbouring homes.
This guide explains how the local planning framework treats daylight and amenity, which adopted policies apply, and how a technical daylight and sunlight assessment supports a robust application.
The planning framework in Rhondda Cynon Taf
The development plan for the area is the Rhondda Cynon Taf County Borough Local Development Plan 2006–2021, which was adopted on 2 March 2011. Although the plan period has ended, it remains the adopted statutory development plan and continues to be used to determine planning applications while the council prepares its Revised Local Development Plan 2022–2037. Applicants should be aware that the emerging replacement plan is progressing, but at the time of writing the 2011 LDP is the document against which proposals are assessed.
Sitting above the LDP is the wider Welsh planning framework. This includes Planning Policy Wales (Edition 12, 2024), Future Wales: the National Plan 2040, and the relevant Technical Advice Notes. Planning Policy Wales places strong emphasis on good placemaking and on protecting the amenity of existing and future occupiers — principles that flow directly into how local daylight and overshadowing matters are judged.
Key adopted policies
Several policies in the adopted LDP are relevant to daylight, sunlight and residential amenity:
- Policy AW 5 (New Development) — sets the criteria for new development, including that proposals should have no significant adverse impact upon the amenities of neighbouring occupiers. Loss of light and overshadowing fall squarely within this amenity test.
- Policy AW 6 (Design and Placemaking) — requires a high standard of design that is appropriate to the local context in terms of siting, scale, height and massing. In the valleys, height and massing decisions directly affect how much light reaches neighbouring properties below.
- Policy AW 10 (Environmental Protection and Public Health) — addresses development that could harm amenity and public health, reinforcing the protection of living conditions.
These criteria-based policies do not set numerical daylight targets themselves. Instead, the council looks to its supplementary planning guidance and to recognised technical standards to judge whether amenity is acceptably protected.
Householder and design guidance
The council has adopted A Design Guide for Householder Development as supplementary planning guidance, alongside guidance on design and placemaking and the development of flats. This householder guidance is based on the all-Wales design guide prepared by the Planning Officers Society for Wales and adapted to the local context. It recognises that extensions and alterations can affect neighbours through loss of daylight and overshadowing, and it expects proposals to be designed so that these impacts are kept to an acceptable level. For larger schemes and flatted development, the council's separate guidance on the development of flats addresses the amenity and spacing of new homes.
How daylight and sunlight are assessed
While the LDP and SPG set the policy expectation, the accepted technical method for measuring daylight and sunlight impacts is the Building Research Establishment guidance. The current edition is BRE BR 209 – Site Layout Planning for Daylight and Sunlight: A Guide to Good Practice (third edition, 2022), supported by the daylight provision standard in BS EN 17037. These documents are the methodology that daylight and sunlight consultants across the UK rely on, and they are referenced as best practice in Wales.
The main tests a report will apply include:
- Vertical Sky Component (VSC) — a measure of the skylight reaching a neighbour's window. As a general rule, retaining a VSC of around 27%, or keeping any reduction to no more than 20% of the previous value, indicates daylight is likely to remain satisfactory.
- Daylight distribution (No Sky Line) — assessing how much of a room can still see the sky after development.
- Annual Probable Sunlight Hours (APSH) — the sunlight reaching windows that face within 90 degrees of due south.
- Overshadowing to gardens and amenity space — checking that at least half of an amenity area receives some sunlight on the spring equinox.
In a borough where terraced rows step up steep gradients, these tests matter more than in flatter areas. A modest rear extension or a new dwelling on the uphill side of an existing home can cast a far longer shadow than the same building would on level ground, so careful modelling is essential.
Why the valley topography matters
The classic Rhondda and Cynon valley pattern — long terraces following the contour, with houses tightly packed and gardens often narrow and short — means that the relationship between buildings is unusually sensitive. South-east to north-west valley orientation, hillside shading from the slopes themselves, and the close spacing of properties all combine to make overshadowing and loss of light a recurring objection in local planning cases. Demonstrating compliance with BRE BR 209 gives both the applicant and the council an objective basis for a decision.
How Fortress Associates can help
Fortress Associates provides clear, robust daylight and sunlight assessments prepared to BRE BR 209 (2022) and BS EN 17037, written to support planning applications across Rhondda Cynon Taf and the rest of the UK. Find out more about our daylight and sunlight report service, or explore the full range on our services page. We work to a 4–5 working day turnaround and ask for no advance payment. To discuss your scheme, please use our contact page.
Sources & further reading
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