When might the council ask for one?
An extension, additional storey or new building may need assessment where it could materially reduce light to neighbours. A report can also be needed to demonstrate that proposed homes will have acceptable natural light. Camden's published requirements identify both effects on adjoining properties and developments whose own daylight may be affected by neighbouring buildings. [1]
The assessment should be proportionate to the site and proposal. Under policy DM2 of the NPPF published on 17 August 2026, additional information should be relevant and necessary for the decision. Ask the council which buildings, rooms and outdoor areas need assessment before commissioning extensive modelling. [3]
What should the report show?
The report should identify the assessment method, the existing situation, the proposed development and the resulting effects. Camden's 2025 validation list refers to the 2022 edition of BRE's site-layout guidance. That is important because some older council web pages still mention an earlier edition. [4]
Ask the assessor to provide a drawing or model reference that makes each tested window, room or space identifiable. The results should be accompanied by an explanation of their significance, not just pages of numbers. Identify any assumptions about neighbouring room layouts or inaccessible properties and explain how those limitations affect the conclusions.
The London Plan's housing-design policies address daylight and sunlight in the context of the site's circumstances. A calculation result should inform a reasoned assessment; it should not be presented as a universal statutory pass mark that settles every planning judgement. [2]
Who prepares it?
Commission someone with relevant daylight-assessment and modelling experience. The architect or designer should provide the correct site geometry and proposal, while the specialist explains the assessment method and its limitations. Camden's requirements envisage specialist daylight and sunlight evidence where the effects warrant it. [4]
A useful appointment should say whether it includes testing design options, preparing the submission report and responding to council comments. Require an update when changes to height, footprint or window design could affect the earlier conclusions.
Coordinate light with other design needs
Increasing glazing is not the only design objective. The London Plan also requires consideration of privacy, outlook and overheating. Review these issues together so a revision intended to improve daylight does not leave another assessment describing an incompatible design. [2]
Is this the same as a right to light?
No. RICS describes a right of light as a private, legally enforceable property right. A planning daylight assessment and a private rights-of-light assessment therefore answer different questions. Where a possible private right could affect the proposal, obtain separately scoped surveying and legal advice rather than assuming the planning report has resolved it. [5]