When considering a new building development in an urban area, concerns are often raised regarding the effects of overshadowing on surrounding buildings. There are two primary considerations: the planning process and the legal liabilities.
The planning process is typically navigated by undertaking a Daylight and Sunlight Assessment, considering guidance prepared by the Building Research Establishment (BRE) [1].
The legal liabilities are considered separately through a Right of Light Assessment. It is not directly related to the planning process and are therefore important to assess even if no planning issues are identified.
Figure 1 ‘Ancient Lights’ signs on a building in Clerkenwell, London [2]
Rights of Light
Right to light can be acquired in several different ways, but the most common is through prescription, under the Prescription Act 1832.
‘When the access and use of light to and for any dwelling house, workshop, or other building shall have been actually enjoyed therewith for the full period of twenty years without interruption, the right thereto shall be deemed absolute and indefeasible’ [3]
This means that the rights are acquired after 20 years of uninterrupted light to a window. For this period to be considered ‘interrupted’, light must be obstructed for a period of at least one year.
Once this right has been acquired, the owner is entitled to ‘sufficient light according to the ordinary notions of mankind’ [4], but this does not mean that they are entitled to completely unobstructed light.
Methodology for Assessing Rights to Light
There are no formal requirements for determining the impact of a development towards rights to light, however the predominant method of assessing this is through the ’50:50 rule’ with consideration of the ‘sky factor’.
50% of the room (measured at a working plane of 838mm above floor level) should have a sky factor of 0.2% or greater, which essentially means that 50% of the room should be able to see at least 0.2% of the sky. Recent court cases have indicated that 55% of the room is now seen as a more appropriate threshold for residential buildings.
If a new development reduces a property’s light beneath this threshold, they may be entitled to remedies against the developer of the new development.
Potential Remedies
The primary remedy for right to light is an injunction to prevent a building from being constructed such that it would obstruct rights to light. This has the potential to cause development delays or even act as a complete showstopper.
An alternative remedy is financial compensation, and it is possible to calculate the value of lost light through the use of Light Standard Rent. It should not however be assumed that developers can simply buy their way out of right of light issues.
It is entirely at the discretion of the courts as to which remedy is offered based on the particular circumstances of each case.
About Pager Power
Pager Power is a dedicated technical consultancy that has been providing independent guidance and advice regarding solar developments, wind farms, and building developments internationally since 2002. Further details about what we services we can provide can be found here. Pager Power has completed over 1,400 glint and glare assessments, over 1,000 aviation/radar impact assessments, over 500 television and radio reception surveys, and over 500 telecommunications impact assessments.
If you are looking for a Right of Light assessment for your proposed building development, please get in touch on our website or call us on +44 (0)1787 319001 and one of our technical team will get back to you.
References
[1] BRE 209
[2] Mike Newman (16th September 2006) from WikiCommons. Accessed on: 26th November 2024.
[3] Section 3, Prescription Act 1832
[4] Colls v Home & Colonial Stores Ltd, [1904] UKHL 1
