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Writer's pictureJames Williamson

Do I Need Planning Permission for an Extension? Guide

Updated: 1 day ago

Are you considering expanding your living space with an extension? Before embarking on your project, it's crucial to understand the planning permission requirements. This comprehensive guide will help you navigate the complex rules and regulations surrounding home extensions.


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Key Considerations Before You Start


Party Wall Act and Neighbourhood Consultation Scheme

Familiarise yourself with the Party Wall Act 1996, which aims to prevent and resolve disputes between neighbours regarding party walls, boundary walls, and excavations near neighbouring buildings. This Act requires you to notify your neighbours if you're planning to build on or near your shared property boundary.


The Neighbourhood Consultation Scheme applies to larger single-storey rear extensions. Under this scheme, you must notify your local planning authority and consult with your neighbours before proceeding with certain extensions.


Listed Buildings and Conservation Areas

If your property is a listed building or located in a conservation area, more stringent rules apply. Always consult with your local planning office for specific guidelines, as these properties often require additional permissions and may have restrictions on the types of alterations allowed.


Understanding the "Original House" Rule

The term "original house" refers to the property as it stood on 1st July 1948, or as it was originally built if constructed after this date. Any previous extensions count towards your current development limits. For instance, if over half the land around the "original house" will be covered by extensions (including existing ones), you'll need planning permission.


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Types of Planning Permission


Full Planning Permission

This requires detailed plans for all aspects of the development and is suitable for complex projects or those falling outside permitted development rights.


Outline Planning Permission

This provides preliminary approval based on general principles, allowing for more design flexibility in the later stages of the project.


Do I Need Planning Permission To Build An Extension?


Not all extensions require planning permission. Many fall under "permitted development rights", but these rights have specific limitations. Here are the key factors to consider:


General Requirements

Planning permission to build an extension is typically needed if:


  • The extension extends forward of the principal or side elevation facing a highway

  • More than half the land around the "original house" will be covered by additions or outbuildings

  • The extension uses materials that differ significantly from the existing house

  • The extension is higher than the highest part of the existing roof

  • The eaves and ridge height of the extension exceed those of the existing house

  • The eaves height is more than 3 metres within 2 metres of the boundary

  • The extension includes verandas, balconies, or raised platforms


Side Extensions

Planning permission is required if:

  • The extension is higher than 4 metres

  • It's more than one storey

  • The width is more than half that of the "original house"


Single-Storey Rear Extensions

Planning permission is needed if:

  • The extension is higher than 4 metres

  • It extends beyond the rear wall of the "original house" by more than 8 metres for detached houses, or 6 metres for other house types


Two-Storey Rear Extensions

Planning permission is required if:

  • The extension extends more than 3 metres beyond the rear wall of the "original house"

  • It's within 7 metres of the rear boundary

  • The roof pitch doesn't match the existing house

  • Side-facing windows aren't obscure-glazed with non-opening elements below 1.7m from the floor


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The Party Wall Act


The Party Wall Act 1996 is designed to prevent disputes between neighbours. You must notify your neighbours if you're:


  • Building on or at the boundary of your two properties

  • Working on an existing party wall or party structure

  • Excavating near a neighbouring building


Neighbour Consultation Scheme


For larger single-storey rear extensions (between 4 and 8 metres for detached houses, or between 3 and 6 metres for other house types), you need to submit a Prior Approval application. This allows neighbours to object, and the local council will investigate any concerns. The determination period is 42 days.


Lawful Development Certificate (LDC)


Even if planning permission isn't required, it's advisable to apply for a Lawful Development Certificate. This provides legal confirmation that your extension complies with permitted development rights.


Costs vary:

  • England - £103

  • Scotland - £101

  • Wales - £85


An LDC can be crucial when selling your property or obtaining a mortgage.


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The 45-Degree Rule


This rule helps ensure your extension doesn't overshadow neighbouring properties. If your extension falls within a 45-degree angle from the centre of your neighbour's nearest window, it's generally considered acceptable. However, this rule is a guideline and not a statutory requirement.


Building Regulations


Remember that even if planning permission isn't required, your extension must comply with building regulations. These ensure the structural integrity, safety, and energy efficiency of your project.


Conclusion


Understanding planning permission requirements is crucial for a successful extension project. If in doubt, always consult your local planning authority or seek advice from a professional planning consultant. For complex projects or listed buildings, professional guidance is invaluable.


FAQs


Q: Are building regulations the same across the UK?

A: No, they vary. England and Wales follow the Building Act 1984, while Scotland follows the Building (Scotland) Act 2003. Northern Ireland has its own regulations under the Building Regulations (Northern Ireland) Order 1979.


Q: What's the difference between building regulations and planning permission?

A: Building regulations ensure structural integrity, safety, and energy efficiency. Planning permission concerns the external appearance, use, and environmental impact of the building.


Q: What is the 4-year rule?

A: The 4-year rule states that after four years, local authorities cannot take enforcement action against unauthorised developments for a change of use to a single dwelling house. However, this rule was phased out in England from 2023.


Q: What is retrospective planning permission?

A: This is sought after building work is completed without prior permission. It can legitimise unauthorised work, potentially preventing fines or demolition orders. However, it's always best to obtain permission before starting work.


For personalised advice on your extension project, contact our expert team at James Williamson Architects. We can guide you through the planning process, design your ideal extension, and ensure compliance with all relevant regulations.

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