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Permitted development: Illuminating what ‘adequate natural light’ might be
The beginning of August 2020 will see the addition of a new permitted development right (PDR) into the Town and Country Planning (General Permitted Development) (England) Order 2015 (GPDO). The new PDR allows two storey extensions to be added to existing residential buildings without planning permission, but subject to prior approval, conditions and limitations (new Part 20 Class A). Other amendments coming into force that day introduce additional prior approval considerations relating to natural light to existing PDRs for changes of use to dwellinghouses. And on 31 August, new permitted development rights for additional storeys on single dwellings and commercial and mixed use buildings and to knock down a vacant commercial or residential building and replace it with a new residential building will come into force, subject to prior approval, conditions and limitations. Amongst the prior approval matters for the PDRs for new dwellings achieved by additional storeys or a new building is a requirement to consider both the effects of permitted extensions on the residential amenity of neighbouring properties -including loss of light- and the ‘provision of adequate natural light’ within the newly created dwellings. The latter requirement applies to all habitable rooms within the proposed residential accommodation. This latter requirement now also applies to PDRs for a change of use to dwellings from offices, shops, casinos, light industrial and agriculture (but not storage). The loss of light to neighbouring properties must be considered in prior approval application to extend single dwellings by adding storeys. At first glance this requirement seems clear enough, however, the wording of the requirement is likely to spark debate on the interpretation of the word ‘adequate’. Natural light studies have been a feature of planning submissions for proposed residential, student, hotel, educational and other buildings for a significant period of time. Planning officers are quite used to seeing studies based on the current Building Research Establishment (BRE) guidance. The BRE guidance provides direction on the daylight and sunlight targets to be applied to new accommodation and states that if a room is to look adequately lit it will need to comply with the Average Daylight Factor (ADF), No-Sky Line / Daylight Distribution (DD) and room depth guidance. However, the values used are based on a suburban context and are often not achievable in an urban environment. As such, the results of testing in built up locations often shows that developments may fall short of the guidance and liaison with Planning Officers is needed to determine what values should be considered appropriate. The conversion of an existing structure often brings with it several limitations, window positions are fixed and internal configurations may be limited by support structures. Add to these restrictions the likelihood that neighbouring structures may be in close proximity and of a significant height and it can be seen that the blanket application of BRE Report guidance would be inappropriate. The limitations brought about by urban environments are discussed in the BRE guidance but clearly defined alternative targets are not provided. It is left to the design team and the local authority to determine / accept revisions to the given guidance. Some local authorities and the GLA have accepted the inevitable deviation from the BRE Report guidance in urban locations. Both the GLA and the London Legacy Development Corporation (LLDC), for example, have supplied guidance that lower daylight values should be considered as appropriate in given urban situations, however, this guidance mostly refers to the effects a proposed development will have on its neighbours. Conversely, some local planning authorities take the view that the BRE guidance should be strictly applied in all settings. Currently the determination of natural light within a residential development is undertaken using ADF, DD and Annual Probable Sunlight Hours (APSH) tests. These tests are being replaced, but for the time being are still the ‘go to’ tests. The BRE guidance provides absolute targets but no discussion on what deviations if any would be appropriate in an urban location. As such the determination of what should be considered adequate natural light requires judgement and is a matter of what planning officers and planning committees are willing to accept. The determination of adequacy is and will inevitably remain a subjective matter and the acceptance of a specific development will continue to depend on the strength of the applicant’s analysis and evidence, and the experience of planning officers. Clearly, where a proposed scheme complies with BRE guidance it will be easy to argue that the natural light is adequate, and small deviations are also likely to cause little discussion. However, where rooms deviate significantly from the current guidance, robust justification will be required and clear discussions will need to be undertaken with officers on the application of alternative tests. Alternative testing methodologies have been in use for decades but are mostly not understood by planning officers, as they do not form part of the BRE guidance. These alternative tests, often used in BREEAM testing of commercial spaces, EFA guidance on school design and design guidance for Healthcare Buildings are mostly based on climate data and often show the duration of given light levels within rooms either for specific days or as an average across the year. These alternative tests have recently been incorporated into British Standards and the BRE guidance is to be revised to suit, however, there is no indication yet on when or if local authorities will apply the new guidance. Clearly the determination of adequacy required under the updated GPDO will depend on site specific criteria. However, precedence will be key with officers and natural light practitioners closely following the first applications to see what is accepted. Lichfields’ Neighbourly Matters team is experienced in undertaking a wide range of natural light studies for new developments, building extensions and property conversions across the UK. This experience and our understanding of alternative assessment methods means that we are well placed to assist developers, architects and local authority officers in navigating prior approval applications through the new GPDO requirements relating to natural light. For further information please contact Toby Rogan-Lyons

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