Neighbourly matters: daylighting and sunlighting

Daylight saving

15 March 2013

The RICS Daylighting and Sunlighting guidance note gives an overview of the way chartered surveyors are expected to provide professional advice and sets standards for its quality, says Alistair Redler

The guidance note is intended to be read in conjunction with the BRE report Site Layout Planning for Daylight and Sunlight 2011 that defines the standards and methods of calculation usually relied on by local authorities when assessing planning applications.

When advising on daylight and sunlight, surveyors can play many different roles, all imposing different levels of detail and standards of advice. For example:

  • acting for developers in assisting with designs to meet standards
  • advising developers for environmental assessments such as BREEAM, the Code for Sustainable Homes, etc
  • representing developers in assisting with obtaining planning permission by reporting on daylight standards within planning policy
  • acting for neighbours to a development in checking or challenging reports submitted by a developer’s consultants
  • advising a local authority on an applicant’s daylight and sunlight report where the calculations or conclusions need to be verified
  • acting for a developer as an expert witness in a planning inquiry
  • acting for a local authority as an expert witness in a planning inquiry.

As with all work carried out, the surveyor taking instruction must be capable and competent to undertake it. Daylight and sunlight calculations are increasingly done by detailed computer analysis, although it is possible to do these manually using standard templates. However, it is necessary for the client to know the detail and calculation process that is going to happen.

For example, opponents to a planning application have only a short period within which to lodge those objections and, by the time a surveyor is approached and instructed, there could be only a few days to complete any analysis. It may therefore be difficult to complete a full computer analysis. But it is possible to perform spot check measurements and a review of the developer’s consultant’s report to provide advice on whether there are valid grounds for an objection and to submit a letter of objection.

Each local authority has its own policy on environmental and neighbour matters, including daylight and sunlight standards, but these are not usually uniform or mandatory. It is therefore acceptable for a surveyor to find a way to write a report to support their client’s planning application. However, the report’s technical data must be honest and accurate, as must the reporting of those results. The report can argue that the results are not contrary to the local planning policy (if it is fair to make that case) or the numerous other factors that are relevant to the local authority’s decision on granting planning approval.

Advice on daylight and sunlight restrictions given at an early stage of the design development will influence the shape and massing of the proposed scheme and it is important that surveyors advise their developer clients of the likelihood of success if the scheme does not fully comply with planning policy. In such cases, and to avoid abortive work, it is frequently sensible to stress early dialogue with the relevant planning officer to agree on the method of assessment and standards to be adopted, together with mitigating arguments.

Daylight Distribution

Figure 1: The daylight distribution test calculates the sky visibility on the working plane within the room

This is important because compliance with the standards in the BRE report will not always be appropriate. It states that it should not be used as a tool of planning policy and that development should not be designed entirely to fit daylight considerations if they do not result in the best design. Alternatively, it is important that developments are not allowed to reduce daylight to neighbouring residential properties to the extent that they are left with substandard amenity that would then cause long-term harm to current and future occupiers. However, there are situations where mitigating reasons can fairly be argued.

One of these is where sites are very open, such as long-term car park sites, petrol stations and low-level industrial units. In that case, there may be some neighbouring properties that currently have very good levels of daylight and sunlight. However, even with a reduction of more than 20% from existing (the recommended allowance in the BRE report) will still leave those properties with substantially higher levels of daylight and sunlight than most of their neighbours who have not had the benefit of being near such an open site up to that point.

Often there are good planning reasons for a more dense development than the daylight standard would impose, particularly where there is a specific need for increased commercial or residential accommodation. Here it would be appropriate to ensure that the neighbouring rooms are left with sufficient internal illuminance and amenity, such as by the Average Daylight Factor method of calculation rather than the Vertical Sky Component method (see the guidance note for details).

Another common situation is where the design of neighbouring properties limits their own access to daylight and sunlight, e.g. where there are deep or recessed balconies, winter gardens or deck access walkways. In such case, the BRE report advises that it may be appropriate to allow leniency to the recommended standards and simply show that the development is not of an inappropriate scale. One way of doing this is to perform calculations as if the balconies or obstructions were not present and therefore show that the development would not reduce the daylight and sunlight by more than 20% from existing.

When advising on mitigating matters the surveyor does, of course, need to be sure that those arguments are valid and justified, particularly if a failure to obtain planning consent will lead their client to appeal the decision. In that case, the surveyor is likely to take on the role as expert witness at inquiry and will need to show that the advice is proper and impartial and be able to withstand cross-examination.

Daylight and sunlight will be an increasing requirement on planning applications throughout the country as it is now required for most applications in residential areas in London

Surveyors advising local authorities should take a sensible and practical view of a report submitted on behalf of an applicant. It can be acceptable to advise that an application that does not meet full planning policy should still be considered to not have a material adverse impact, if it is fair to do so considering the full circumstances of the development and its effect on the neighbouring properties. However, they should make this clear so that the planning officer, and ultimately the planning committee, can make a fully informed decision.

Daylight and sunlight will be an increasing requirement on planning applications throughout the country as it is now required for most applications in residential areas in London. Surveyors have a role to properly and accurately calculate and advise on these matters but should not fall into the trap of treating them as mandatory requirements. On the other hand, we do need to balance the frequent wish of developers to maximise their profit against genuine long-term loss of amenity and harm that can be caused to neighbouring residents.

Alistair Redler is a Partner with Delva Patman Redler and a member of the panel that developed the RICS Daylighting and Sunlighting guidance note

Further information

Related competencies include: T021, T051, T077