How can rights of light impact your development plans?

How can rights of light impact your development plans?

With space for new homes at a premium and the resulting trend to build upwards, the ‘rights of light’ issue remains ever prevalent. This grey area has often been a cause for challenge in residential development, whether an extension to a single property or a developer seeking to move forward with a substantial new site.

As confusion still reigns over rights of light versus daylight and sunlight amongst many architects and developers, these issues it shows no signs of letting up – especially when you consider that apartments will account for 50 per cent of the planned new build housing stock in the UK.

Let’s examine the major differences between the two – and the all-important considerations that must be made throughout the planning process.

Rights of light

The most important point to make about a landowner’s ‘absolute and indefeasible’ right to the easement of light, is that it is totally separate to the planning process – despite what some architects and developers still believe.

Instead, it is a private right between landowners – one which must be considered by the developer and its consultants during the planning process to prevent any future pitfalls, but for which planning approval does not demonstrate compliance.

This easement (a right to cross or otherwise use someone else's land for a specified purpose) gives the landowner the right to receive light through defined apertures in buildings situated on the land.

There are numerous ways to acquire a right to light, but the most common is via long enjoyment – if a property is more than 20 years old you can generally assume that it’s apertures enjoy prescriptive rights, under Section III of the Prescription Act 1832.

How is it measured?

The measurement of ‘sufficient light’ is not calculated via sunlight or by artificial light but is measured geometrically from the area of sky visible at desk height through the specified aperture – a complex calculation which uses the Waldram Method of Assessment.

This method uses a uniform sky dome to calculate what percentage of sky visibility is required to create lumens of light.

Alongside, consultants may undertake a radiance-based assessment, based on daylight analysis to pinpoint the location of small or moderate losses of light. This can potentially demonstrate that the impact is not noticeable because the loss of light is already in an area which would require additional electrical lighting.

Daylight and sunlight

In contrast, daylight and sunlight is a means through which a Local Planning Authority can determine if a development will cause material harm to an adjoining occupier’s amenity.

As part of the planning process, it is mainly used for dwellings and users with a higher expectation of natural daylight and sunlight such as hospitals, ecclesiastical or education buildings, using different assessment criteria to rights of light. In such cases, the Local Authority will be guided by the Building Research Establishment (BRE) document ‘Site Layout Planning for Daylight and Sunlight’, A guide to good practice, Second Edition.

Any one of a number of daylight assessments are used, including the 25 Degree Rule, Vertical Sky Component (VSC), No Sky Line (NSL) measuring the daylight distribution within a room or Average Daylight Factor (ADF). Methods of calculating sunlight include Annual Probable Sunlight Hours (APSH) and overshadowing to external amenity space is considered.

Steps to success

Like many aspects in the planning process, the key is to plan ahead and complete the necessary due diligence. Rights of light must be considered early, ideally during or before the initial massing studies, because redesign later can be expensive.

If possible, explore alternative massing options to remove any ransom position that adjoining owners may be able to generate or to negate impacts to amenity – providing the desired massing can still be maintained.

Forward-thinking developers may even consider rights of light/daylight and sunlight during the purchase of the site to understand any potential risks and outline initial compensation budgets.

Above all else, formulate the strategy early. Consider the daylight and sunlight planning implications in conjunction with rights of light. Failure to do so could be damaging to any project.

For more information about rights of light or daylight and sunlight, or to discuss your next project, contact Anthony Harris on or 020 7125 0112.

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