permitted development guide for house extensions


What is permitted development ?

Most homes have Permitted Development rights which mean that some types of building work do not need Planning Permission. Permitted Development (PD) rights can be a really good thing because:

  • You do not need to apply for Planning Permission, so you save time and money
  • The design does not have to meet local planning policy, so you get more freedom

Using PD rights you might be able to build more or extend further than if you applied for Planning Permission, and you may be able to add more value to your home. In this post we will guide you through the details you need to know to make the best use of your Permitted Development rights.

Permitted Development Guide For House Extensions

Permitted Development Rights

how much can you build?


Maximising PD Rights For House Extensions

All of the coloured parts of this diagram were built to extend this house under Permitted Development rules, without requiring a planning application for any of it.

Rear and side extensions were built under Class A of the Permitted Development regulations. Roof extensions and alterations including dormers and gable ends were added under Class B. Other alterations to the roof including removing a chimney and adding roof lights were done under Class C. Finally landscaping changes were made under Class F.

Planning and PD

not all house extensions need planning


Can you build without planning approval ?

Yes if your work complies with all of the requirements of Permitted Development then it would not require planning permission. This is a good option for many homeowners because it can offer a chance to build more than would otherwise be approved under Planning. However it is very important to understand all the PD rules that you need to meet. The Town and Country Planning (General Permitted Development) (England) Order 2015, often known as GPDO 2015, is the Act of Parliament that puts in to law the type of building work that can be done without Planning Permission from the local authority.

What is Permitted Development ?

general permitted development order (GPDO)


What PD Rights Include

It can be a surprise to see how much you can build under Permitted Development. Full rules for each PD class in GPDO 2015 are set out in the Government guide PD Rights for Householders which gives clear technical guidance. Permitted Development rights are split in to 8 Classes (A – H) with separate rules for each Class, but most work falls in to one of the first 5 classes:


  • Enlargement, improvement or alteration – Class A
  • Additions to the roof – Class B
  • Other alterations to the roof – Class C
  • Porches – Class D
  • Outbuildings – Class E

Permitted Development

checklists for project types


Is Your Project Permitted Development?

You can build more than most people realise, but to help work out if your project is PD just follow these steps:

  1. Run through the relevant checklist below for the type of work you want to build.
  2. Check there are no Article 4 directions that remove PD rights from your property.
  3. Submit an application for a Certificate of Lawfulness to confirm the work is PD.


Check if your project is PD

These quick checklists should start to give you an idea if your work is PD. If you can check off each item for your kind of project, then there is a good chance that you don’t need planning permission.


Single Storey Rear Extensions

Single storey rear extensions can be built in Class A of the GPDO. A rear extension is the most common householder PD project.

  • Max height 4m
  • Max height 3m if within 2m of any boundary
  • Extension depth max 4m (8m with prior approval) if detached house
  • Max extension 3m (6m with prior approval) if semi-detached or terraced
  • No cladding in Conservation Area


Two Storey Rear Extensions

Two storey rear extensions can be built in Class A of the GPDO. You need to make sure that there is a big enough gap to the boundary to meet the rules.

  • Max height to match existing house
  • Height max 3m if within 2m of any boundary
  • Max extension from rear wall of 3m
  • Side windows fixed and obscure glazed to 1.7m above floor
  • Not in Conservation Area


Side Extensions

Side extensions can be built in Class A of the PD rules. They are only allowed to be one storey and are not allowed in a Conservation Area.

  • Max height 4m
  • Single storey only
  • Max width 50% of original house
  • Not in Conservation Area


Roof Extensions

Roof extensions like dormer windows or hip-to-gable conversions can be built in Class B of the GPDO.

  • Max height of dormer or loft extension to match existing roof
  • Max increase in loft volume of 50m3 (40m3 for terraced house)
  • Eaves retained and extension set in 200mm
  • Side windows fixed and obscure glazed to 1.7m above floor
  • No extension forward of original front roof slope
  • Not in Conservation Area


Roof Lights

Roof lights can be built in Class C of the PD rules. They can be built on any roof slope, including the front, and are even allowed in Conservation Areas.

  • Max protrusion 150mm above roof slope
  • Roof lights on side roof slopes fixed and obscure glazed to 1.7m above floor



A Porch can be built at any entrance door under Class D of the GPDO 2015.

  • Max external area 3m2
  • Max height 3m
  • Not within 2m of boundary with highway



Outbuildings such as sheds; garden rooms or garden offices can be built in the curtilage of the property as Class E Permitted Development.

  • Max roof height 4m, reduced to 2.5m if within 2m of boundary
  • Max eaves height of 2.5m
  • Must not be used as a separate house
  • Not built in front of house, and not at side of house if in Conservation Area



A Patio, decking or other hard surface such as a driveway can be built under Class F of the PD rules.

  • Must be made of porous material if at front of house
  • Must not be a raised more than 300mm



Chimneys or flues can be built or taken down under Class G of the GPDO.

  • Max height 1m higher than existing roof
  • Not on front or side roof pitches facing road in Conservation Area

Get the right approval

permitted development or planning


Differences Between PD and Planning Approvals

It may seem ridiculous but the planning system is set up so that there are lots of projects that could only ever be built under Permitted Development and would never be granted Planning Permission. We have worked on lots of projects where if the drawings were submitted to the council using a Planning Application form they would be rejected, but if the exact same drawings were submitted using a Lawful Development Certificate form for PD they would be approved.

That might sound crazy. It might sound as if a Council should approve a planning application if the work is PD anyway – but they won’t. If you make a planning application and it does not meet the local planning guidance, then it will be refused even if the work is PD.


PD Can Be The Only Way To Get Permission

Some common householder projects that break most local authority planning policy and would be refused under a planning application, but which could still meet all of the Permitted Development rules and be appoved under PD are:

  • Rear extension more than 3m deep
  • Side extension that can be seen from the street
  • Hip-to-gable roof extension
  • Dormer window roof extension
  • Roof light on front roof slope

Larger Extensions Under Permitted Development

prior approval process


Rules for Larger Permitted Development Extensions

For a detached house the max Permitted Development extension depth is increased from 4m to 8m. For all other types of house, the max Permitted Development extension depth is increased from 3m to 6m. There are some additional rules that must be met if you want to use this relaxation. But in short, you must let the Council know about your plans so that they can consult with your neighbours. This is known as Householder Prior Approval.


Householder Prior Approval

Once you give the Council your plans to build a PD extension under the relaxed rules they will write to your neighbours and give them 21 days to comment. The Council will only consider comments that are to do with your neighbour’s amenity, such as loss of light or privacy. Keep in mind that if your neighbour objects, you may still get permission

PD in special planning circumstances

conservation areas and the green belt


Permitted Development in Conservation Areas

Some people think that homes within Conservation Areas do not have Permitted Development rights. This is not right, and in fact a lot of Permitted Development rights will still normally be in place. These are shown in the table at the start of this post, and include rear extensions, outbuildings and even porches. Although PD rights are limited in a Conservation Area, they are not taken away as standard.

The trouble is that within Conservation Areas (if you ask them) the Council will often just tell people to make a Planning Application. This is not good as it gives the Council the chance to refuse the work under Local Planning Policy. The key is to find out what Permitted Development rights are in place. Here’s what you need to know to get this done:


Article 4 Directives

If the Council want to remove Permitted Development rights they have 2 main ways to do this:

  1. They can put a Condition on a planning approval to remove PD rights for future work.
  2. They can pass an ‘Article 4’ directive to remove some or all PD rights from an area.

So if you want to have work done in a Conservation Area that would not meet Planning Policy, but could be PD then it is well worth checking both of these out. If there are no conditions or article 4 directives then you may still have PD rights even though you are in a Conservation Area, and you could then submit an application for a Certificate of Lawfulness to confirm.


PD in the Green Belt

The Green Belt surrounds much of London and includes a lot of Surrey. In the Green Belt there is a presumption against new work, and this can be a problem for those that want to extend their home. But over the years we have completed many projects on Green Belt Land using PD rights. On the whole Council Planning Policy is very strict in the Green Belt and we’ve worked on projects where any planning app at all would be refused. There can still be a way forward though, as it can be that Permitted Development rights exist, even in the Green Belt. If the Council have not passed an Article 4 then PD can still be an option.


Is Green Belt ‘Article 2(3) land’?

The short answer is no. Permitted Development is restricted on Article 2(3) land, but this means a National Park, the Broads, an AONB, World Heritage Site or a Conservation Area. In fact, as Green Belt Land is not normally any of these things, it can be that full PD rights are in place with no restrictions at all. Again it is well worth checking this out as it can be the case that a Permitted Development extension is the only way to build in the Green Belt.

Confirm your project is PD

lawful development certificates


Apply For a Certificate of Lawful Development

So let’s say you are pretty certain that you can build all of the work you are planning under Permitted Development, and do not require planning permission. To confirm this it is a good idea to make an application for a Certificate of Lawful Development. This will prove that the work is Permitted Development, and is good to have and to keep in your files. Here’s the best way to make sure that this all goes well and that you get approval first time:

  • Get a good architect to plan and draw up the work.
  • Make sure you show all of the key dimensions on your drawings. You also need to include a north point and a scale bar.
  • Use the Planning Portal to set up the application forms, or ask your architect to do it
  • Make sure you state on the form that the extensions are PD (Class A). Give all of the key sizes to show clearly that it is PD.
  • State on the form that the loft extension is PD (Class B). Show a volume calculation based on the Planning Portal calculator.
  • Make sure you state on the form that the roof lights are PD (Class C). And state that they will not be more than 150mm above the roof.
  • State on the form that the Patio is PD (Class F).
  • You will then need to pay the Council fee of £86 (which is about half the fee of a Planning Application). If all goes well then after about 6 weeks you should get your Certificate of Lawful Development.

More Guidance

all posts

We have written a number of posts which provide information and guidanceto anyone considering a project. These include advice on design and planning of new homes, renovations and extensions.



If you have a project you would like to discuss with us then just drop us a line using this form and we will get back to you. Or call us in our London studio on 020 3920 9805.

We will be happy to help and we look forward to hearing from you.



+44 (0)20 3920 9805


45 Dresden Rd, London, N19