- What Permitted Development Rights Actually Mean
- The Standard Rules for Single-Storey Rear Extensions
- The Larger Home Extension Scheme
- Two-Storey Extensions Under Permitted Development
- Side Extensions: Where the Rules Get Tighter
- London-Specific Restrictions You Must Check
- What Counts as the "Original House"
- Do You Need a Lawful Development Certificate?
- Party Wall Agreements
- What Happens If You Build Outside PD Rules
- Planning Your Extension with the Right Team
- FAQs
If you're thinking about extending your home, one of the first questions you'll face is whether you need planning permission. The answer usually comes down to permitted development rights — and getting it wrong can be expensive.
In 2026, the rules remain broadly unchanged from the Town and Country Planning (General Permitted Development) (England) Order 2015. But London homeowners face specific conditions that catch people out more often than you'd expect. This guide covers what you can build without a planning application, where the limits sit, and what to check before anything else.
What Permitted Development Rights Actually Mean
Permitted development (PD) rights let you carry out certain building works without submitting a full planning application to your local council. The government grants these rights automatically, but they come with strict conditions covering size, height, materials, and position.
Think of them as a defined set of rules you must stay within — not a blank cheque to build whatever you like.
If your project fits within those rules, you can proceed without formal planning permission. If it doesn't, you'll need to apply — and in London, that can add months and real uncertainty to your timeline.
The Standard Rules for Single-Storey Rear Extensions
For most houses in England, a single-storey rear extension can be built under permitted development provided it meets all of the following:
- It does not extend beyond the rear wall of the original house by more than 4 metres for a detached house, or 3 metres for any other type (semi-detached, terraced, end-of-terrace)
- The maximum height does not exceed 4 metres
- The eaves height does not exceed 3 metres if the extension sits within 2 metres of a boundary
- The materials are similar in appearance to the existing house
- It does not cover more than half the garden area of the original house
These limits apply to the original house as it stood on 1 July 1948, or as it was first built if constructed after that date. Any extensions already added to the property count against your allowance.
The Larger Home Extension Scheme
Since 2019, a prior approval process has allowed larger single-storey rear extensions under what's commonly called the Larger Home Extension Scheme. In 2026, this route still applies and permits:
- Up to 8 metres beyond the rear wall for detached houses
- Up to 6 metres for all other house types
This isn't automatic. You must notify your local planning authority and allow a 42-day consultation period during which neighbours can raise objections. The council then decides whether the impact on neighbouring amenity is acceptable. If no concerns are raised, you can proceed.
It's worth considering if you need more depth than standard PD allows — but it does add time and a degree of uncertainty to your project.
Two-Storey Extensions Under Permitted Development
Two-storey rear extensions are permitted under PD only if:
- The extension does not project more than 3 metres beyond the rear wall of the original house
- It sits no closer than 7 metres to the rear boundary
- The roof pitch matches the main house as far as practicable
- Any upper-floor windows on the side elevation are obscure-glazed and non-opening below 1.7 metres from the floor
Two-storey side extensions are not permitted under PD and require a full planning application.
Side Extensions: Where the Rules Get Tighter
Single-storey side extensions are permitted under PD, but the conditions are strict:
- The extension must not exceed half the width of the original house
- It must be single storey with a maximum height of 4 metres
- It must not sit forward of the principal elevation
In designated areas — which includes a significant portion of London — side extensions under PD are often removed altogether. This is one of the most common points of confusion for London homeowners.
London-Specific Restrictions You Must Check
London adds layers of complexity that don't apply elsewhere. Several conditions reduce or remove PD rights entirely, and they affect a large proportion of London properties.
Article 4 Directions
Many London boroughs have issued Article 4 Directions, which remove some or all permitted development rights in specific areas. These are common in conservation areas, but they also apply to certain residential streets that carry no formal conservation designation.
If your property sits within an Article 4 area, you'll need planning permission for works that would otherwise be permitted. Check this with your local planning authority or through the council's planning portal.
Conservation Areas
If your property is in a conservation area, PD rights for side extensions are removed entirely. You cannot build a side extension without planning permission, regardless of size.
Rear extensions in conservation areas are still permitted under PD, but cladding the exterior with stone, artificial stone, pebble dash, render, timber, plastic, or tiles requires permission.
Listed Buildings
If your property is listed, permitted development rights do not apply. Any works — including internal alterations — require listed building consent. This affects many Georgian and Victorian properties across central and inner London.
Flats and Maisonettes
Permitted development rights for extensions apply only to houses. If you own a flat or maisonette, you'll need planning permission for any extension or significant alteration.
What Counts as the “Original House”
This is where many homeowners trip up. The original house means the property as it was on 1 July 1948, or as first built if constructed after that date. Previous owners may have already used part or all of the PD allowance with earlier extensions.
Before assuming you have the full 3 or 4 metre rear extension allowance, check what's already been built. Your local council's planning portal will show historical planning applications, and a measured survey of the existing footprint will confirm what's already been added.
Do You Need a Lawful Development Certificate?
Even when your project clearly falls within PD limits, you're not required to apply for a Lawful Development Certificate (LDC). That said, getting one is strongly advisable.
An LDC is a formal document from the council confirming your works are lawful. It protects you when you sell the property — buyers' solicitors routinely ask for evidence that extensions were built with the appropriate permissions. Without one, you risk delays or renegotiation at the point of sale.
The application costs around £206 in England and takes roughly eight weeks. For the protection it provides, it's almost always worth doing.
Party Wall Agreements
Permitted development rights don't override the Party Wall Act 1996. If your extension involves work on or near a shared wall, excavation within 3 to 6 metres of a neighbouring structure, or a new wall on the boundary, you must serve notice on your neighbours under the Act.
This is entirely separate from planning. You can have full PD rights and still need to follow the party wall process. Failing to do so can lead to disputes and injunctions that stop your build in its tracks.
What Happens If You Build Outside PD Rules
If you build an extension that exceeds PD limits without obtaining planning permission, the council can issue an enforcement notice requiring you to alter or demolish the works. This is rare when the breach is minor, but it's a genuine risk — particularly in conservation areas and Article 4 zones where councils monitor development more closely.
Selling a property with an unlawful extension is also difficult. Buyers and their solicitors will identify the issue, and you may need to obtain retrospective planning permission or indemnity insurance before the sale can proceed.
Planning Your Extension with the Right Team
Understanding the rules is one thing. Applying them to your specific property, in your specific borough, with your specific design goals — that's where the real complexity begins.
The most practical approach is to confirm your PD position early, before you commit to a design. A good design and build team will check your PD allowance, identify any Article 4 or conservation area restrictions, and advise on whether planning permission is needed before a single drawing is produced.
At MVV, the process starts with exactly that kind of groundwork. From concept to completion, the same team handles your design, manages any planning requirements, and delivers the finished build — so nothing falls through the gaps between different contractors or consultants.
If you want to understand what your extension might cost before committing to anything, the instant cost estimator at themvv.co.uk gives you a ballpark figure in minutes, with no obligation.
FAQs
Do I always need planning permission for a house extension in London?
No. Many extensions can be built under permitted development rights without a planning application. However, London has a higher proportion of conservation areas, listed buildings, and Article 4 Directions than most of England, so always verify your property's status before assuming PD applies.
How far can I extend my house under permitted development in 2026?
For a standard single-storey rear extension, the limit is 4 metres for a detached house and 3 metres for a semi-detached or terraced house. Under the Larger Home Extension Scheme, these limits increase to 8 metres and 6 metres respectively, subject to a prior approval process with your local council.
What is an Article 4 Direction and how do I know if it affects my property?
An Article 4 Direction is a council order that removes some or all permitted development rights in a specific area. You can check whether your property is affected through your local planning authority's website or by contacting the planning department directly.
Can I build a side extension under permitted development?
A single-storey side extension can be built under PD if it doesn't exceed half the width of the original house and meets the height limits. In conservation areas and Article 4 zones, however, side extensions typically require full planning permission regardless of size.
What is a Lawful Development Certificate and do I need one?
A Lawful Development Certificate is a formal document from the council confirming your works are lawful under PD rules. It's not legally required, but it protects you when selling the property and is strongly recommended for any extension built under permitted development.
Does permitted development apply to flats and maisonettes?
No. Permitted development rights for extensions apply only to houses. If you own a flat or maisonette, you'll need planning permission for any extension.
What is the difference between permitted development and the Larger Home Extension Scheme?
Standard permitted development is automatic and requires no application — only compliance with the size and design rules. The Larger Home Extension Scheme allows larger extensions but requires you to notify the council and complete a 42-day prior approval process before work can begin.
Getting your PD position right at the start saves time, money, and stress further down the line. If you're planning an extension and want to understand your options, start with a free cost estimate at themvv.co.uk.