The 6-Metre and 8-Metre Extension Rules (UK Guide)

Contents

• Can You Really Build a 6 or 8-Metre Extension Without Full Planning Permission?

• What Are the 6-Metre and 8-Metre Rules?

• Who Qualifies? Eligibility Checklist

• Important note on previous extensions

• Everything Your Extension Must Comply With

• The Step-by-Step Prior Approval Process

• What Happens If a Neighbour Objects?

• Practical Measurement Guide

• What If You're in a Conservation Area?

• Article 4 Directions

• Do You Need Building Regulations Approval?

• Should You Apply for a Lawful Development Certificate (LDC)?

• Common Mistakes to Avoid

• Frequently Asked Questions

• Thinking About a Rear Extension 

Can You Really Build a 6 or 8-Metre Extension Without Full Planning Permission?

Yes, and thousands of UK homeowners do it every year.

Under what is now a permanent part of England's permitted development (PD) rights, you can build a single-storey rear extension of up to 6 metres (semi-detached or terraced house) or 8 metres (detached house) without a full householder planning application, subject to the Prior Approval process where required This is far larger than most people realise.

There is a catch: extensions beyond the standard 3m/4m depths require you to go through a short process called Prior Approval, which involves notifying your council and consulting your immediate neighbours. But it is not a full planning application, but a lighter approval process with a narrower scope for refusal, it is significantly cheaper, faster, and the council’s ability to refuse is limited to specific amenity impacts on neighbouring properties.

This guide explains everything you need to know – the rules, the measurements, the process, what can go wrong, and how to maximise your chances of a smooth approval.

All depths measured from the original rear wall of the property.

What Are the 6-Metre and 8-Metre Rules?

The 6m and 8m extension rules are part of England's Permitted Development Rights, specifically under Part 1, Class A of the Town and Country Planning (General Permitted Development) (England) Order 2015.

Originally introduced as a temporary "Larger Home Extension Scheme" in 2013, these enhanced depth limits were made permanent in June 2019 and are now embedded in standard permitted development legislation. Since September 2020, they apply as part of your automatic PD rights rather than as a separate scheme.

In plain English: The legislation allows these large extensions because it recognised homeowners need more space and that sensibly designed rear extensions need not harm neighbours in most cases.

Back to top

Who Qualifies? Eligibility Checklist

Before going any further, confirm your property qualifies:

You CAN use the 6m/8m rule if your property is:

• A single dwellinghouse (terraced, semi-detached, or detached)
• Located in England
• Not subject to an Article 4 Direction removing your PD rights
• Not a flat, maisonette, or converted building

You CANNOT use the 6m/8m rule if your property is:

• A flat or maisonette (PD rights do not apply)
• Located on Article 2(3) land, which includes: conservation areas, Areas of Outstanding Natural Beauty (AONBs), National Parks, World Heritage Sites, and Sites of Special Scientific Interest (SSSIs)
• Subject to a planning condition that has removed your PD rights
• A listed building (you would need Listed Building Consent)
• Located in Scotland, Wales, or Northern Ireland (different rules apply)

Important note on previous extensions

Your permitted development allowance is measured from the original rear wall of the property – meaning the house as first built, or as it stood on 1 July 1948. If a previous owner already extended the property, that depth counts towards your limit. For example, if a previous owner added a 3-metre extension on a semi-detached house, your remaining allowance under Prior Approval is only 3 further metres (to reach 6m total), not a fresh 6 metres.

Back to top

Everything Your Extension Must Comply With

Meeting the depth limit alone is not enough. Your extension must satisfy all of the following conditions under Part 1, Class A to qualify as permitted development:

1. Single Storey Only

The extension must be single storey. Two-storey rear extensions are subject to different and more restrictive PD rules (maximum 3m from the rear wall regardless of property type).

2. Maximum Height: 4 Metres

The total height of your extension must not exceed 4 metres, measured from the highest point of the natural ground level.

3. Eaves Height Near Boundaries

If any part of your extension falls within 2 metres of a property boundary, the eaves height of that part must not exceed 3 metres. This rule exists to limit the overbearing impact on neighbours directly beside you.

4. Width Restriction

If your extension extends beyond the side wall of the original house at any point, its total width cannot exceed half the width of the original house at its widest point.

5. Not Beyond the Side Elevation

An extension that projects beyond the side elevation of the original house is treated differently and is subject to additional restrictions applying to side extensions.

6. 50% Curtilage Rule

The total footprint of all buildings on your land – including the proposed extension, any existing extensions, sheds, garages, and outbuildings – must not exceed 50% of the total land area around the original house.The 50% limit is calculated against the original house as it stood in 1948. All existing extensions and outbuildings count towards this total

7. Materials Must Match

The external appearance of your extension – brickwork, render, roof tiles, window frames – must be similar in appearance to the materials used on the existing house. Note: this requirement does not apply to conservatories.

8. No Balconies, Verandas, or Raised Platforms

These features are not permitted under Class A. If you want a balcony or veranda, you will need a full planning application.

9. Roof Height

The ridge and eaves of your extension must not exceed the ridge and eaves height of the original house.

Back to top

The Step-by-Step Prior Approval Process

Any extension that exceeds the standard depth (over 3m for attached homes, over 4m for detached) up to the 6m/8m maximum requires Prior Approval through what is known as the Neighbour Consultation Scheme. Here is how it works:

Step 1: Prepare Your Application Documents

You will need to submit the following to your local council via the Planning Portal or direct submission:

• A completed notification form for a proposed larger home extension
• A written description of the proposed development including the length, maximum height, and eaves height of the extension
• A block plan or site plan showing the site and the proposed extension
• The addresses of all adjoining properties (those sharing a boundary with your land)
•  

Step 2: Pay the Application Fee

The current fee for a Prior Approval application for a larger home extension is approximately £120–£240, depending on your local council. This is significantly lower than a full householder planning application, which costs £258 from April 2025. Some councils charge nothing in specific circumstances, such as where the works relate to disability access.

Step 3: Council Notifies Neighbours

Once your application is validated, the council writes directly to the owners and occupiers of all adjoining premises – not just your immediate neighbours, but anyone sharing a boundary. They are given a minimum consultation period, typically 21 days, to raise objections.

Step 4: Two Possible Outcomes After Consultation

If no neighbours object: The council must confirm that Prior Approval is not required. In other words, you are automatically entitled to build, provided your extension meets all the other PD conditions. The council has no discretion to refuse at this point.

If any neighbour objects: The council is then required to assess the impact of your proposed extension on the amenity of all adjoining premises – not just those that objected. Critically, the council can only consider material planning considerations related to amenity impact. These typically include:

• Loss of natural light or sunlight
• Overbearing or oppressive sense of enclosure
• Loss of outlook
• Privacy and overlooking

The council cannot refuse on grounds of: the extension being too big in principle (Parliament already decided 6m/8m is acceptable), design aesthetics, parking, or any other subjective preference.

Step 5: Decision Deadline

The council must make its decision within 42 days of the application being validated. If no decision is issued within 42 days, you can appeal for non determination. In practice, you should not begin construction without written confirmation or a formal appeal outcome.

Back to top

What Happens If a Neighbour Objects?

Neighbour objections are a common source of anxiety for homeowners, but it is important to understand how limited the council's powers actually are once an objection is made.

What neighbours CAN legitimately object on:

• Your extension will block significant light to their windows (loss of light to neighbouring windows)
• The extension will feel oppressive or overbearing from their garden or windows
• The extension will create overlooking or privacy issues at first-floor level
•  

What neighbours CANNOT validly object on:

• They simply don't like the look of it
• It will reduce their property value
• It will cause noise during construction
• They disagree with the 6m/8m rule in principle
• It is too large for the street

Councils are required to apply the legislation properly, not to substitute their own preferences. However, in practice, some councils do refuse applications once any objection is received – sometimes reflexively, citing "overbearing impact" without fully engaging with the evidence. This is where appeals become important.

Appeal success rates for larger home extensions are notably high. Planning inspectors apply the legislation correctly, understanding that Parliament deliberately allowed these depths. Inspectors do not approach these appeals with the same hostility that some local planning authorities still exhibit, and refusals are frequently overturned on appeal.

If your Prior Approval is refused, you can appeal to the Planning Inspectorate. A refusal is not the end of the road – it often simply means minor revisions to height, layout, or materials are needed before resubmitting.

Back to top

Practical Measurement Guide

The most common mistake homeowners make is measuring from the wrong wall. Here is how to measure correctly:

"Original rear wall" means the rear wall of the house as it was originally constructed. If a previous owner added a conservatory or extension, you do NOT measure from the back of that addition – you measure from the original wall behind it.

How to find the original rear wall:

1. Check the original floor plans from when the property was built (often available from the Land Registry or with your title deeds)
2. Look at the building's structure – you can often identify original walls from changes in brick or blockwork
3. Consult with an architect or planning consultant who can assess this on your behalf
   

A worked example:

A semi-detached house has an existing 2-metre rear conservatory added by a previous owner. The homeowner wants to extend as far back as possible. The original rear wall is the wall behind the conservatory. The maximum depth allowed under Prior Approval is 6 metres from that original wall. The existing conservatory already uses 2 metres of that allowance, so the homeowner can add a further 4 metres beyond the conservatory (making 6m total from the original rear wall).

What If You're in a Conservation Area?

If your property is on Article 2(3) land – which includes conservation areas, AONBs, National Parks, World Heritage Sites, and SSSIs – the enhanced 6m and 8m allowances do not apply.

In these areas, your maximum rear extension depth under standard permitted development is:

• 4 metres for a detached house
• 3 metres for all other houses

If you want a larger extension on designated land, you will need to submit a full planning application. The criteria used to assess such applications will typically be stricter, with greater weight given to the visual impact on the character of the area.

Back to top

Article 4 Directions

Some councils have removed permitted development rights in specific areas through Article 4 Directions. These are common in conservation areas but can also apply in other locations where the council has identified a need for greater planning control.

If an Article 4 Direction applies to your property, you cannot rely on PD rights at all and must submit a full planning application for any extension. You can check whether your property is subject to an Article 4 Direction by searching your local council's planning portal or contacting the planning department directly.

Do You Need Building Regulations Approval?

Yes. Even if your extension is permitted development and goes through Prior Approval rather than planning permission, it will still need to comply with Building Regulations. Building Regulations are separate from planning rules and cover the structural integrity, fire safety, thermal performance, drainage, and ventilation of your extension.

You will need to:

• Submit a Building Regulations application to your local authority's Building Control department (or a private Approved Inspector)
• Ensure your contractor builds to the approved standards
• Obtain a completion certificate at the end of the build

Failure to obtain Building Regulations approval can cause significant problems when you come to sell the property.

Should You Apply for a Lawful Development Certificate (LDC)?

A Lawful Development Certificate is an optional but strongly recommended document that formally confirms your development is lawful. While it is not strictly required if your extension qualifies as permitted development, obtaining one provides:

• Legal certainty that your extension was built lawfully
• Protection if planning rules change in future
• Reassurance for buyers and mortgage lenders when you come to sell

You can apply for an LDC through the Planning Portal. The fee is typically half the cost of a full planning application. Applications typically up to 8 weeks, although this can vary by authority.

Back to top

Common Mistakes to Avoid

1. Measuring from the wrong wall. Always measure from the original rear wall of the house, not from any existing extensions or conservatories.

2. Ignoring the 7-metre boundary setback. On smaller plots, your extension may hit this limit before you reach the 6m/8m depth maximum.

3. Starting work before Prior Approval is confirmed. You must not begin construction until the council has confirmed Prior Approval is not required, or has granted Prior Approval. Starting early can render your development unlawful.

4. Assuming you have full PD rights. Always check for Article 4 Directions, planning conditions on your title deeds, and whether your property is on designated land before proceeding.

5. Getting the materials wrong. Using visually distinct materials for your extension – even if the structure itself complies with all dimensional rules – can cause a refusal on materials grounds.

6. Ignoring the 50% curtilage rule. If you have multiple outbuildings, an existing extension, or a small plot, you may already be close to the 50% limit without realising it.

Frequently Asked Questions

Thinking About a Rear Extension?

Understanding the rules is one thing. Turning them into a home you love is another.

At Marraum, we're RIBA Chartered Architects based in Cornwall with decades of experience designing extensions, renovations, new builds, and barn conversions that genuinely work for the people who live in them. Every project begins with your story – how you live, what you need, and what your space could become.

We handle everything from the first sketch through to planning, Prior Approval applications, technical design, and construction coordination – so you never have to navigate the process alone. And because we use immersive VR technology, you can step inside your design and experience every room before a single brick is laid.

We also take sustainability seriously. Not as a buzzword, but as a commitment – to honest conversations about energy efficiency, thoughtful material choices, and buildings that serve you well today without costing the planet tomorrow.

Back to top