How Apertures Affect Your Right of Light Claim

By Neil Goddard · 7 August 2026

When people think about rights of light, they tend to focus on the building next door or the development blocking their view. But the starting point for any claim is actually much closer to home. It begins with your windows. In legal terms, these are called "apertures," and they play a central role in whether a right of light exists and how strong your claim might be.

An aperture is simply an opening in a building through which light passes. Windows are the most obvious example, but skylights, glass doors, and even fanlights can qualify. The key question is whether that aperture has received light without interruption for at least 20 years. If it has, a legal right to that light may have been acquired under the Prescription Act 1832. You can read more about what a right of light is and how the 20-year rule works in practice.

Not every opening in your property will automatically count. The aperture needs to have been in its current position, or substantially the same position, for the full prescriptive period. If you replaced a small window with a larger one five years ago, only the original smaller opening would carry the established right. The enlarged portion would need to start its own 20-year clock. This catches a lot of people out, especially after renovations.

There is also the question of what counts as a "defined" aperture. A gap in a fence or an open courtyard does not qualify. The law requires a specific opening in a wall or roof that admits light to an interior space. Courts have consistently held that the right attaches to the aperture itself, not to the building as a whole. So if you have ten windows on a rear elevation, each one is assessed individually.

This matters enormously when a new development is proposed nearby. A surveyor will examine each qualifying aperture and model the light it currently receives versus the light it would receive after construction. That modelling process, often using Waldram diagrams and specialist software, determines whether the reduction crosses the threshold for an actionable interference. If you want to understand how compensation is calculated, the aperture analysis is where it all starts.

One detail that often surprises property owners is that blocked-up windows can still matter. If a window was bricked up but the opening is still visible in the structure, there may be an argument that the right has not been entirely abandoned. However, abandonment is a complex area and the facts of each case vary significantly. Courts look at the intention behind the blocking up and how long the aperture has been out of use.

For leaseholders, the position adds another layer of complexity. The right of light typically belongs to the occupier of the property, but the aperture itself is part of the building's structure. This means both freeholders and long leaseholders may have an interest, depending on the terms of the lease. Understanding whether you can make a claim often depends on untangling these ownership questions.

If you are a homeowner concerned about a nearby development, the first practical step is to identify every aperture on the affected side of your property. Note the size, position, and how long each window has been in place. Photograph them. This basic record can be incredibly useful if you later need to instruct a rights of light surveyor.

Developers sometimes try to argue that certain windows are not qualifying apertures, perhaps because they serve bathrooms or stairwells rather than habitable rooms. While the type of room can affect the valuation of a claim, it does not necessarily prevent a right from existing. A window that has received light for 20 years is a window that has received light for 20 years, regardless of what sits behind it.

Getting to grips with how apertures work gives you a much clearer picture of your position. It is the foundation on which every rights of light assessment is built. If you are unsure about your situation, you can request a free assessment to find out where you stand before taking any further steps.

Reference: Prescription Act 1832, s.3; Colls v Home and Colonial Stores Ltd [1904] AC 179