Rights of Light in London: What They Are and How They Affect Extensions

A right of light is a type of easement — a legal right that attaches to a property and entitles the property's owner to receive natural light through defined windows or apertures that have received light for at least 20 years.

**How rights of light arise:** In England, rights of light most commonly arise by 'long use' — a window that has received natural light for 20 years or more, without interruption and without the neighbouring landowner's permission, acquires a legal right to that light under the Prescription Act 1832. The right attaches to the window opening, not the view — it protects light, not outlook.

**What the right protects:** A right of light does not protect all light received through a window — only a sufficient amount for the comfortable use of the building for its ordinary purposes. Courts assess rights of light using the '50-50 rule' — whether 50% or more of the room measured at working plane height (typically 850mm) would be left in 'gromb shadow' (illuminated by less than 0.2% of the available sky light) after the development is built. This is a technical assessment carried out by a specialist rights of light surveyor using daylight/sunlight modelling software.

**Who holds rights of light:** Rights of light are attached to the building (the dominant tenement) — the neighbouring owner, whether owner-occupier, freeholder, or leaseholder, may hold the right. In flats, individual leaseholders may hold rights of light to their own windows independently of the freeholder.

**Who needs to consider rights of light:** Rights of light is a property law matter — it is entirely separate from planning law. Planning permission for an extension does not override rights of light, and obtaining planning permission does not protect a developer from a rights of light claim. A planning permission does not even confirm that no rights of light infringement occurs — planning authorities do not assess rights of light as part of the planning process.

Rights of light is most likely to be relevant where:

**A new extension is close to neighbouring windows:** A ground-floor or first-floor rear extension built close to a side or rear boundary, adjacent to neighbouring windows that face the building, is the most common scenario. Dense London terraces — where rear extensions on adjacent properties are separated by a narrow gap, or where the extension is on the boundary — are the typical context.

**The extension is tall relative to neighbouring windows:** A two-storey extension built close to a neighbouring property's windows creates a significantly greater shadow than a single-storey structure at the same distance. A tall extension on the boundary in a terrace or semi-detached situation is the highest-risk scenario.

**The neighbouring property's windows are old:** Windows that have been in place for 20+ years are the ones most likely to have acquired rights of light. If the neighbouring property was built before 2000, its windows should be assumed to potentially have rights of light unless there is evidence to the contrary.

• **Scenarios where rights of light is less likely to matter:**
• •Loft conversions — adding rooflights or dormers to the rear of a house rarely affects light received by neighbouring ground or first-floor windows
• •Single-storey extensions set well away from the boundary
• •Extensions on the front of a property (where the neighbouring windows typically face the street, not the extension)
• •New-build developments on previously undeveloped land (where there were no pre-existing windows)

**How to assess the risk:** For any extension project where the structure will be close to neighbouring windows, a preliminary rights of light assessment is advisable. A specialist rights of light surveyor can carry out a desktop daylight/sunlight analysis using software (typically Radiance or similar) to indicate whether the proposed extension is likely to infringe the neighbours' rights. If the preliminary assessment suggests a risk, a more detailed analysis — and potentially negotiation with the neighbouring owner — should follow before works begin.

• **What a neighbouring owner can do:**
• If a neighbouring property owner believes their rights of light have been or will be infringed by a proposed development, they can:
• •Seek an injunction to prevent the construction from proceeding (the most serious remedy — courts have granted injunctions requiring buildings already under construction to be partially demolished)
• •Claim damages for the loss of light (an alternative to an injunction, assessed as a proportion of the development value 'released' by the infringement)

The courts have in recent years moved toward damages rather than injunctions in some cases — but the risk of an injunction requiring partial demolition is real, particularly where the developer proceeded with works despite being aware of the risk.

**Risk management for London extension projects:**

• •**Early assessment:** Instruct a rights of light surveyor to assess the risk as part of the design stage, before planning is submitted. If a risk is identified, the design can be adjusted to reduce the infringement.

• •**Noteholder consent:** If a rights of light risk is identified, the most effective mitigation is to negotiate an agreement with the neighbouring property owner that releases or acknowledges the right in exchange for agreed compensation. This is a commercial negotiation and typically costs £2,000–£10,000+ in combined professional fees and compensation payments, depending on the significance of the infringement and the neighbouring owner's negotiating position.

• •**Rights of light insurance:** If noteholder consent cannot be obtained (for example, where the neighbouring owner is uncooperative or cannot be traced), rights of light insurance is available. This insures the developer against the cost of defending a rights of light claim and the cost of any damages or injunction. Premiums are typically 0.5–2% of the development value and the insurance must be obtained before any contact is made with the noteholder (once you have contacted them, the policy will not be issued). Rights of light insurance should be viewed as a last resort — it transfers the financial risk but does not resolve the underlying issue.

**Extinguishing rights of light:** Rights of light can be extinguished by a Local Authority (under the Rights of Light Act 1959) through registration of a notice at Land Charges. This is rare in residential extension contexts but is used occasionally on larger development schemes.