A planning appeal decided in January 2025 has clarified a point that every developer and architect commissioning a daylight assessment in England should understand: the methodology you choose is not a minor technical detail — it can be the difference between 72 per cent of your flats meeting daylight targets and only 27 per cent.
The Mast Quay Phase 2 case in Woolwich, Royal Borough of Greenwich, put the question of which daylight standard applies squarely before an inspector. The answer has wide implications for any residential scheme across the UK.
What Happened at Mast Quay Phase 2
Mast Quay Phase 2 was a build-to-rent development in Woolwich completed by Comer Homes Group. The Royal Borough of Greenwich served an enforcement notice in 2023, arguing that the as-built development was materially different from the approved plans and that the changes left residents with unacceptably low daylight levels.
The developer’s daylight consultants calculated that 72.4 per cent of habitable rooms in the completed building met “recommended BRE guidelines” for natural light. This figure was produced using the UK National Annex to BS EN 17037:2018, which sets relaxed targets compared with the core standard.
Lichfields Natural Light Consultancy, acting for the council, re-ran the same room-by-room data using the core BS EN 17037:2018 targets. Their result: just 27 per cent of rooms met the minimum lux targets.
Both parties agreed on the measured daylight levels inside the flats. The dispute was which set of targets those figures should be compared against.
The Core Standard Versus the UK National Annex
BS EN 17037:2018 is the European standard for daylight in buildings. It sets three target levels — minimum, medium, and high — expressed as illuminance (lux) that rooms should achieve for at least half of daylight hours across the year.
The UK National Annex to BS EN 17037 provides a separate, lower set of targets for situations where external obstructions make meeting the core targets unrealistic. The annex was designed for genuinely constrained locations such as basement flats or sites hemmed in on all sides by tall neighbouring buildings.
The developer argued that, because Woolwich is a dense urban environment, the National Annex targets were appropriate. Inspector John Braithwaite disagreed.
The Inspector’s Decision: Context Is Everything
In his written decision dated 9 January 2025, the inspector found that “it is the standard set out in BS(EN) 17037:2018 itself that must be applied” to the Mast Quay site.
His reasoning was direct: the National Annex is not a general urban discount that any city-centre development can claim. The Mast Quay site faces a wide river to the north, a dual carriageway to the south, and open distance to the east. The physical surroundings did not justify treating this as a hard-to-light location. Applying the National Annex to a site with genuinely good sky access was, the inspector found, inappropriate.
The finding meant that, on the correct methodology, the majority of completed flats had “obviously substandard levels” of daylight and that “some residents have less than acceptable living conditions.”
Despite the daylight failures, the inspector granted planning permission for the development as built, subject to cladding changes, and ordered Comer Homes Group to pay Greenwich Council £7.82 million. The methodological ruling, however, stands as a clear signal to the industry.
What This Means for Future Daylight Assessments
The Mast Quay decision is now a live piece of case law that planners, inspectors, and appellants can cite. Its practical implications are worth understanding before you commission a daylight and sunlight report for any new development.
Being urban does not automatically justify the National Annex
The National Annex is intended for sites where external obstructions genuinely constrain sky access — not simply because a development sits within a city. If your site has clear sky to one or more aspects, an inspector may require core BS EN 17037 targets to be applied. An assessment that relied on the National Annex without adequate site-specific justification could face challenge at appeal or judicial review.
Methodology choices must be explicitly justified
A daylight report that adopts the National Annex without explaining why should raise a flag during planning review. The accompanying narrative must demonstrate that the site’s physical context — nearby buildings, retained structures, road widths, topography — genuinely warrants the lower targets. Local planning authorities are increasingly alert to this since the Mast Quay ruling, and several London boroughs now commission independent peer reviews of submitted daylight reports before granting permission.
The gap between methodologies can be substantial
At Mast Quay, switching from the National Annex to core targets moved compliance from 72 per cent to 27 per cent. That is not a marginal difference. If your scheme passes under the National Annex but fails under core targets, you need to understand that gap and design to close it, rather than rely on a methodology that may not survive scrutiny at appeal.
Where BRE BR 209 (2022) Sits in All of This
It is important to note that BRE BR 209 (2022) — which remains the primary document used to assess the effect of a new development on its neighbours’ daylight — operates separately from BS EN 17037. The BRE guidance covers the Vertical Sky Component (VSC) and Annual Probable Sunlight Hours (APSH) tests that apply to windows in existing surrounding buildings.
BS EN 17037, by contrast, is primarily concerned with the internal daylight quality of the proposed development itself — the light experienced by future occupants. The Mast Quay ruling applies specifically to this internal assessment. Our guides to BS EN 17037 for UK architects and VSC, NSL and APSH explain both frameworks in more detail.
How Fortress Associates Can Help
Whether you are bringing a new residential scheme forward or navigating an enforcement challenge, choosing the right daylight assessment methodology from the outset is essential. At Fortress Associates, we prepare daylight and sunlight reports that are transparent about methodology, properly justified against site context, and structured to withstand planning authority scrutiny and independent peer review. We deliver reports within 4–5 working days of receiving drawings, with no advance payment required. Contact us to discuss your scheme.
Sources & further reading
- Lichfields: Mast Quay appeal decision — daylight testing must reflect the context of the area (January 2025)
- Royal Borough of Greenwich: Mast Quay developers ordered to pay council £7.82 million
- BRE BR 209 (2022): Site Layout Planning for Daylight and Sunlight
- National Planning Policy Framework (NPPF) — GOV.UK
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