Ancient lights

Right to light is a form of easement in English law that gives a long-standing owner of a building with windows a right to maintain the level of illumination. It is based on the Ancient Lights law. The rights are most usually acquired under the Prescription Act 1832.

In effect, the owner of a building with windows that have received natural daylight for 20 years or more is entitled to forbid any construction or other obstruction that would deprive him or her of that illumination. Neighbours cannot build anything that would block the light without permission. The owner may build more or larger windows but cannot enlarge their new windows before the new period of 20 years has expired. It is also possible for a right to light to exist if granted expressly by deed, or granted implicitly, for example under the rule in Wheeldon v. Burrows (1879).

Once a right to light exists, the owner of the right is entitled to "sufficient light according to the ordinary notions of mankind": Colls v. Home & Colonial Stores Ltd (1904). Courts rely on expert witnesses to define this term. Since the 1920s, experts have used a method proposed by Percy Waldram to assist them with this. Waldram suggested that ordinary people require one foot-candle of illuminance (approximately ten lux) for reading and other work involving visual discrimination. This equates to a sky factor (similar to the daylight factor) of 0.2%. Today, Waldram's methods are increasingly subject to criticism and the future of expert evidence in rights to light cases is currently the subject of much debate within the surveying profession.

After the Second World War, owners of buildings could gain new rights by registering properties that had been destroyed in bombings and the period was temporarily increased to 27 years.

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