If you are planning to build or extend on Ynys Mon, it pays to understand the daylight requirements in the Isle of Anglesey before you submit. The Isle of Anglesey County Council (Cyngor Sir Ynys Mon) expects new development to protect the daylight and sunlight enjoyed by existing homes and to provide acceptable daylight for new occupiers. This guide sets out the policy framework for the island, the technical guidance assessors rely on, and how to prepare a well-evidenced application.
The planning framework that applies on Anglesey
Planning applications on Anglesey are determined against the adopted development plan and national policy for Wales. The adopted plan is the Joint Anglesey and Gwynedd Local Development Plan 2011–2026, adopted on 31 July 2017. Although Anglesey shares this statutory plan with neighbouring Cyngor Gwynedd, the Isle of Anglesey County Council is the planning authority that decides applications on the island.
The two councils ended their joint planning policy working arrangement on 31 March 2023. As a result, the Isle of Anglesey County Council is now preparing a new Anglesey-only Local Development Plan covering 2024 to 2039. Until that replacement plan is adopted, the 2017 Joint LDP remains the development plan for the island and the basis for decisions.
It is worth noting one key difference from Gwynedd: the whole of Anglesey is administered by the County Council for planning. Unlike Gwynedd, no part of the island lies within Eryri (Snowdonia) National Park, so there is no separate park planning authority to consider here. The defining landscape constraint on Anglesey is instead the Isle of Anglesey Area of Outstanding Natural Beauty (a National Landscape), which covers much of the coastline and influences the design and scale of development near it.
Sitting above the local plan are the national documents for Wales: Planning Policy Wales (Edition 12, 2024), Future Wales: the National Plan 2040, and the relevant Technical Advice Notes, including TAN 12: Design. The English National Planning Policy Framework does not apply in Wales.
Which Anglesey policies deal with daylight and amenity?
The Joint LDP does not set a single fixed “daylight figureâ€. Instead daylight and sunlight are weighed as part of the broader tests of good design and the protection of residential amenity. The two key policies are the same Joint LDP policies that apply across the plan area:
- Policy PCYFF 2 – Development Criteria. This requires that proposals must not cause an unacceptable adverse impact on the health, safety or amenity of occupiers of local residences, other land uses or the characteristics of the locality. Loss of light, overshadowing, overlooking and loss of privacy are all assessed under this policy.
- Policy PCYFF 3 – Design and Place Shaping. This requires high-quality design that respects the site and its surroundings, protects important local features, and safeguards amenity — which includes maintaining adequate daylight to existing and proposed dwellings.
On Anglesey these policies are read alongside the island’s particular character. The coastal AONB/National Landscape, the towns of Llangefni (the administrative centre) and Holyhead (the island’s largest town and a major Irish Sea ferry port), and a generally low-lying, open landscape all shape how the council weighs the scale, massing and overshadowing impact of a proposal. A scheme that would be modest in a dense city street can read very differently against Anglesey’s open coastal settings.
Welsh-language and cultural considerations also run through the Joint LDP, reflecting the strong presence of the Welsh language on Ynys Mon. These do not alter daylight methodology, but they form part of the community and design context the council assesses.
How daylight and sunlight are actually measured
Because the policies set the aim rather than the calculation, assessors on Anglesey — as throughout the UK — apply established best-practice guidance to show that amenity is protected. The recognised reference is the Building Research Establishment guide BRE BR 209, “Site Layout Planning for Daylight and Sunlight†(2022 edition), supported by the British Standard BS EN 17037 on daylight in buildings.
A daylight and sunlight report applies the numerical tests these documents set out, including:
- Vertical Sky Component (VSC) – skylight reaching a neighbour’s window, with a guideline of around 27% retained, or no less than 0.8 times the former value.
- No-Sky Line / Daylight Distribution – how far daylight reaches into a room.
- Annual Probable Sunlight Hours (APSH) – sunlight to windows and amenity areas, especially those facing within 90 degrees of due south.
- Overshadowing of gardens and open spaces, normally tested on the 21 March equinox.
A thorough BR 209 assessment provides the County Council’s officers with objective evidence to apply PCYFF 2 and PCYFF 3, and helps applicants resolve potential problems before submission.
When is a daylight assessment worth commissioning?
Consider a daylight and sunlight report where a proposal is taller or deeper than its neighbours, sits close to a boundary, adds windows that overlook adjoining property, or where an infill plot in Llangefni or Holyhead requires new homes to be tested for their own internal daylight. Evidence provided up front reduces the risk of objection, delay or refusal.
How Fortress Associates can help
Fortress Associates provides our daylight and sunlight report service to BRE BR 209 (2022) and BS EN 17037 for sites across Anglesey and the rest of the UK. We assess the impact on neighbouring properties and the daylight available to your own scheme, and set our findings within the relevant Joint LDP policies and the Welsh planning framework. We also prepare Building Regulations drawings. Reports are typically delivered within 4–5 working days, with no advance payment required. To discuss your site, please get in touch.
Sources & further reading
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