What’s the 45 Degree Rule for Extensions?
During building construction, the 45-degree rule ensures that no new developments will unnecessarily cause natural light to obstruct the neighbouring properties. The rule is a crucial guideline under planning regulations to assess potential light disruption especially when building extensions.
The 45-degree rule is a crucial regulation that affects building development, especially for rear and side extensions. In this blog, discover the intent, significance, and guidelines required for using this important planning regulation.
In general, building a rear extension or a side extension may seem a straightforward project when compared to other types of renovations. But if you couple it with a semi-detached house or a terraced property, the same rear extension can suddenly give you a lot to think about.
The Usual Suspects
Executing a semi-detached or a terraced rear extension come with many potential challenges. Being fully aware of the permitted development rights to specifically ensure what’s allowed and what’s not, how much you can extend beyond the rear wall, along with restrictions on height, are all factors that play decisive role under the purview of planning permission.
While the above considerations have become quite known lately, and so can be anticipated in advance, but what may come out of syllabus is the 45-degree rule.
The 45-degree rule is a crucial regulation that can quite surprisingly turn a straightforward rear or side extension to being one of the most intricate extensions to pull off. Without due consideration for the rule will result in legal action by those affected by it.
What is the 45-degree Rule?
The 45-degree rule is a metric used by most planning councils to ensure that any extension work carried out in a house does not prevent access to light to the neighbouring property through windows.
How to Understand the 45-degree Rule?
The rule assumes an imaginary line drawn from the neighbouring property at an angle of 45-degree and dictates that any extension of the adjacent property should not pass beyond the line.
Horizontal Metric
Let’s assume your property is where the extension is being done. The line considered is usually imagined to be drawn from your neighbour’s property.
The line is drawn on a horizontal plane at an angle of 45 degrees from the center point of the nearest ground-floor window of a room of your neighbour’s property. So, from an aerial view/top view, the extension you are planning should not project beyond the angle of 45 degrees. If the extension projects beyond the 45-degree line, then it means you are obstructing the ‘right to light’ of your neighbour.
Horizontal metrics are usually considered for single-storey extensions.
Vertical Metric
Here, all considerations remain the same that applies for horizontal metric. The only difference is that vertical metrics are usually considered for two-storey extensions.
Key Considerations for the 45-degree Rule
To avert any confusion regarding this intricate regulation, let’s summarise few key factors that are crucial to consider primarily when planning a rear extension –
- The 45-degree rule is only applicable to windows of habitable rooms such as a living room, study room, kitchen, bedroom
- The rule is not applicable to non-habitable rooms such as windows of utility rooms, or bathrooms.
- The 45-degree rule is assessed considering both the plan view and the side view (elevation).
- In case there is no window, glass doors or patio doors may also be considered for scrutiny.
- If it’s a case of a double-storey extension, the rule would apply to a window at a higher elevation which can be the window in the first storey or in the second storey.
- The BR209, part of The Building Research Establishment (BRE) is a guide to site layout planning for daylight and sunlight. The guide is usually used by local authorities as a reference to assess if any proposed developments prevent access to light to nearby properties.
How Strict is the Law for a 45-degree Rule Breach?
- Violating the 45-degree rule though may not be a legal binding by the authorities, but it will definitely enforce some actions by the violator. In some cases, there may not be any action by the planning council and matters will have to be settled between the two parties.
- Supposing there is a case where the breach occurred involves a very negligible projection beyond the 45-degree line, then the respective planning officer will take charge, and decide the course of action. Such matters will usually end in a mutually favourable way without disputes.
- In some cases, if there is an extension you notoriously want them to happen, and if that extension violates the 45-degree rule, the planning officer may suggest you to lower the levels of your home. For such situations, seeking the help of a structural engineer will be necessary.
Rules May Change
If there is one thing that is constant, it is the variation of rules. Councils in different regions may follow different rules. Some councils do not consider the 45-degree line from the center of the neighbouring window, while some consider from the closet side. While some councils follow the BRE guidelines, some may create their own rules.
Regardless of whether the rules change from region to region, the factors affecting planning application remain the same throughout. Below are the factors that are considered by most planning councils during assessing applications –
- Height of the proposed planning application.
- Scale of the property to be extended.
- Orientation of the building to be extended with respect to the neighbouring property.
- Proximity of the proposed extension from the neighbouring property.
Conclusion
Before submitting the planning application to the council, it is important to consult the local planning authority to make sure you are fully aware of the rules and how they apply.
The 45-degree rule is an important rule under the ambit of planning permission. Checking the considerations, and consulting a building professional like a structural engineer may be decisive. Being fully abreast of the rules is important which helps in a peaceful living and to avoid any personal legal disputes or bitter incidents from neighbours.
If you are looking for any guidance or advice on such planning matters, feel free to contact our experts at Extension Architecture.
