Daylight and Sunlight Assessments in Hillingdon

Loss of light to a neighbouring property is one of the most frequently raised objections in Hillingdon, and a clear daylight and sunlight assessment is often what allows officers to grant permission with confidence. Whether you are extending a family home in Ruislip or Ickenham, altering a property in Uxbridge or Hayes, or bringing forward a larger residential scheme in West Drayton, Yiewsley or Northwood, the impact of your proposals on surrounding homes will usually need to be demonstrated - and the responsibility of doing so sits with the applicant.

At Sunlight Assessments, we prepare BRE-compliant daylight and sunlight assessments for planning applications across the London Borough of Hillingdon. Our reports are clear, technically robust, and written around the specific policy tests Hillingdon applies when determining applications.

When is an assessment needed in Hillingdon?

Not every application requires a formal study, but one is commonly expected where:

• Extensions that extend close to a boundary with a neighbouring property, particularly where habitable rooms face the affected elevation
• New residential developments where neighbouring properties may lose access to natural light
• Applications where the Local Planning Authority has identified daylight and sunlight as a material planning consideration
• Side and rear extensions or loft conversions in tightly built Victorian and Edwardian terraces, where neighbouring windows may be particularly close to the proposed works
• Conversions and changes of use where new habitable rooms are proposed

If you are unsure whether your scheme requires an assessment, we are happy to advise on this at no cost.

Hillingdon's planning policy in detail

Hillingdon determines applications against its Local Plan, made up of Part 1: Strategic Policies (adopted 2012) and Part 2: Development Management Policies (adopted January 2020), read together with the Mayor's London Plan. The Development Management document contains the detailed criteria officers use day to day, and it is here that daylight and sunlight are most directly addressed.

The key policy is DMHB 11, 'Design of New Development', which requires that development proposals do not adversely impact on the amenity, daylight and sunlight of surrounding properties and areas. The supporting text is specific about method: the council expects the impact of development to be assessed following the most recent version of the Building Research Establishment's "Site layout planning for daylight and sunlight: A guide to good practice", and it identifies living rooms, dining rooms and kitchens as the habitable rooms that should be tested in adjoining dwellings.

Importantly, Hillingdon's policy builds in a degree of flexibility. Reflecting the National Planning Policy Framework and London Plan, it recognises that the BRE figures are guidelines rather than fixed limits, and that an appropriate degree of judgement is needed when applying them - particularly where a proposal makes efficient use of land. This means results are weighed in their context rather than treated as a simple pass or fail, which makes a well-reasoned assessment especially valuable.

It is worth noting that Hillingdon no longer maintains a standalone residential extensions design guide; the relevant guidance now sits within the Local Plan itself. For the numerical assessment we apply the current BRE guidance, BR 209: Site layout planning for daylight and sunlight (2022 edition), using its established tests of VSC, NSL and APSH.

You can review Hillingdon's adopted Local Plan at hillingdon.gov.uk/local-plan and the council's wider planning policy and guidance at hillingdon.gov.uk/planning-policy.

How the assessment works

We use the methodology set out in BRE BR 209 to assess the impact of proposed development on daylight and sunlight. The key tests we carry out include:

Vertical Sky Component (VSC): This measures the amount of sky visible from the centre of a window. BRE guidance recommends that a VSC of 27% or more is generally considered adequate. Where a development results in a VSC that is less than 0.8 times its former value, the reduction may be noticeable to occupants.

No-Sky Line (NSL): This assesses the distribution of daylight within a room by plotting the line beyond which no sky is visible. Where the area of a room that can receive direct skylight is reduced by more than 20%, occupants are likely to notice a deterioration in the quality of daylight.

Annual Probable Sunlight Hours (APSH): This test is used to assess access to sunlight for windows that face within 90° of due south. It considers both the winter and annual totals to determine whether sunlight losses are likely to be material.

Where appropriate, we also carry out sun-on-ground studies to assess the impact on garden or amenity spaces.

What our Hillingdon report includes

Our daylight and sunlight assessments for Hillingdon planning applications typically include:

• A clear description of the proposed development and the surrounding context
• Identification of all relevant neighbouring windows and amenity spaces
• VSC and NSL calculations for affected neighbouring properties
• APSH calculations where required
• A comparison of results against BRE BR 209 benchmarks
• A professional assessment of whether any identified impacts are likely to be considered material in planning terms
• Recommendations for design amendments where required, to help reduce impacts and support approval

All reports are produced by qualified consultants with experience of working across the London Borough of Hillingdon.

Get in touch

If you are planning a development in Hillingdon and would like to discuss whether you need a daylight and sunlight assessment, please get in touch. We offer a free initial consultation and can turn around a report within 5 working days of receiving the necessary information.