Right to Light: Can a Neighbour's Extension Block Your Light?

What is the right to light and how does it affect planning permission? How to protect your daylight when a neighbour wants to build.

Loss of light is one of the most common concerns when a neighbour submits a planning application for an extension, new building, or raised structure. The law around light is complex because two separate systems are at play: planning law (which assesses daylight and sunlight impact as part of the planning decision) and property law (the legal "right to light" that can exist independently of planning).

Loss of Light in the Planning System

When assessing a planning application, officers consider the impact on neighbouring properties' daylight and sunlight. This is a material consideration - meaning the council must take it into account.

How is it assessed?

Most councils use the BRE Guide "Site Layout Planning for Daylight and Sunlight" (commonly known as the BRE Guide) as their assessment framework. The key tests are:

The 25-degree rule

A simple initial check. If you draw a line at 25 degrees from the centre of the lowest window on the neighbouring property, and the proposed development stays below that line, it is unlikely to cause a significant loss of light. If the development breaks the 25-degree line, a more detailed assessment is needed.

Vertical Sky Component (VSC)

This measures how much of the sky is visible from a window. The BRE Guide suggests that a window should retain at least 27% VSC, or at least 80% of its former value. If a proposed development reduces the VSC below these thresholds, the impact may be considered significant.

Daylight Distribution (No-Sky Line)

This measures how far into a room the sky can be seen from working plane height (850mm). If the area of the room that can see the sky is reduced to less than 80% of its former value, the impact may be significant.

Annual Probable Sunlight Hours (APSH)

For windows facing within 90 degrees of due south, the BRE Guide recommends that they receive at least 25% of annual sunlight hours, with at least 5% in winter months. If the proposed development reduces sunlight below these levels (or below 80% of the former value), the impact may be significant.

Important caveat

The BRE Guide is guidance, not law. Councils are not obliged to follow it rigidly - they must consider the context. In dense urban areas, lower daylight and sunlight levels are expected and accepted. In suburban or rural areas, the standards carry more weight. A development in inner London that fails the BRE tests may still be acceptable; the same development in a village might not be.

The Legal Right to Light

Separately from the planning system, there is a legal right to light under English law. This is a property right (technically an "easement") that can be acquired if a window has received natural light for 20 or more years without interruption (under the Prescription Act 1832).

If a right to light exists and a new development would substantially reduce it, the affected property owner can:

• Seek an injunction - a court order requiring the offending development to be modified or demolished. Courts have ordered the removal of buildings that breach the right to light, though this is becoming rarer
• Claim damages - financial compensation for the loss of light. Courts increasingly award damages rather than injunctions, especially where demolition would be disproportionate

Key points about the right to light

• It is a private legal right - completely separate from the planning system. Having planning permission does not override a right to light
• It applies to light through defined apertures (windows), not to open land or gardens
• The test is whether sufficient light remains for the ordinary use of the room, not whether any light is lost. The standard threshold is that at least 50% of the room should receive adequate natural light (the "50/50 rule")
• Not all windows acquire the right - it must have been enjoyed for 20+ years. New windows, or windows in buildings less than 20 years old, may not have this right

How to Protect Your Light

When a planning application is submitted

1. Review the plans carefully - look at the height, depth, and proximity of the proposed development relative to your windows
2. Object on daylight/sunlight grounds - reference the BRE Guide and your council's design guide. Be specific about which windows are affected
3. Request a daylight/sunlight assessment - for larger developments, ask the planning officer whether a BRE assessment has been submitted. If not, request one
4. Commission your own assessment - for significant developments, a chartered surveyor can prepare a daylight/sunlight report on your behalf (£500-2,000)

Right to light protection

1. Register a "light obstruction notice" - under the Rights of Light Act 1959, you can register a notional screen with the Land Registry to prevent a right to light being acquired over land you own. This is a defensive measure if you own land and want to preserve your ability to develop it in future
2. Seek legal advice early - if you believe a proposed development will breach your right to light, consult a solicitor or chartered surveyor specialising in rights of light before the development starts. It is much harder (and more expensive) to challenge after construction

Permitted Development and Light

If a neighbour's extension is built under permitted development rights, the council has no power to control its impact on your light through the planning system. However, your private right to light still applies - permitted development does not override property rights. If a PD extension breaches your right to light, you can still pursue a legal remedy through the courts.

Stay Informed

The earlier you know about a proposed development, the more effectively you can respond. Search for planning applications near you on Planning Signal and set up alerts to be notified when new applications are submitted in your area.