Use the table of contents to find out more about extensions.


domestic extensions

For the purpose of this webpage, “extension” means any physical addition to the side, rear or front of an existing house that increases its floorspace. It could be an addition to one or multiple floors. We have a separate page on loft conversions – you can access it using the button below.


The short answer is, it depends. If your house benefits from permitted development rights, you will be able to construct certain types of domestic extensions without any need to apply for planning permission. Click the button below to find out more about what sites have permitted development rights and how to find out

You can also find out more about the different types of domestic development – including extensions, outbuildings, hard surfaces, fences and solar panels – that can be carried out using permitted development rights by clicking the button below.

If your site does not benefit from permitted development rights or you would like to construct a type of extension that is not covered by permitted development rights – including most front extensions and two storey side extensions – you’ll need to submit a householder planning application for your local council’s full consideration. Click the button below to find out more about the planning application process.

Permitted development extensions

The tables below contain the most important rules and restrictions for the main types of permitted development extensions. These are:

  • single storey rear extensions
  • larger single storey rear extensions
  • two storey (plus) rear extensions
  • single storey side extensions
  • front extensions (porches only).

Please note the rules appearing in these tables are not exhaustive and there are various other rules and limitations that apply to all permitted development extensions. For example, the house’s eaves height cannot be increased and external materials must have a similar appearance to the existing house (conservatories excluded).

Single storey rear extensions

Height (max)4 metres
Distance beyond original rear wall (max)4 metres if house is detached
3 metres for all other house types

Larger single storey rear extensions

Height (max)4 metres
Distance beyond original rear wall (max)8 metres if house is detached
6 metres for all other house types

Two storey (plus) rear extensions

Distance from rear site boundary (min)7 metres
Distance beyond original rear wall (max)3 metres

Single storey side extensions

Height (max)4 metres
Width (max)Half the width of the original house

Porches (outside any external door)

Height (max)3 metres
Total area (max)3 square metres
Distance to site boundary (min)2 metres

Prior approval applications

The permitted development right to construct larger single storey rear extensions is “subject to prior approval”. This means that unlike most permitted development rights, you must submit an application to your Local Planning Authority (this is normally your local council) prior to commencing works.

Once they’ve received your application, your local council will contact your immediate neighbours. If any of your neighbours object, the council must assess the impact of the extension on neighbouring properties. This will include an assessment of its impact on daylight and overshadowing etc..

If the council considers the extension’s impact is unacceptable, they will refuse prior approval and you must not proceed. Click the button below to find out more about making a prior approval application.

Lawful development certificates

If your domestic extension complies with all the permitted development rules and is not a larger single storey rear extension, you are not obliged to submit any form of planning application. You can get on with building straight away*. However, we strongly advise you to apply for a Lawful Development Certificate prior to commencing works.

*You must always ensure your building works comply with building regulations even if no planning permission is required. Click the button below to find out more about building regulations.

Avoid common pitfalls…

This is because permitted development rules are lengthy, complex and interlinked. They are not always easy to understand, interpret or apply to a given site or scenario and even local councils get it wrong on a regular basis. There are many technical pitfalls that the average householder or uninformed developer can stumble into unawares. 

For example, calculating heights can get complicated when the site is on sloping ground. Similarly, restrictions on the size and siting of domestic extensions can be difficult to calculate where a house has stepped or curved walls.

Other conditions and limitations are ambiguous or open to interpretation. For example, there are restrictions on certain householder extensions if they would “front” a highway. In some circumstances, whether or not a highway is “fronted” is open to interpretation – it depends on the distance to and angle with the road.

If you construct a permitted development extension and later discover that you’ve misunderstood or misapplied one of the many permitted development rules, it won’t be permitted development and you could be required to demolish it and put the site back to its former condition (or else spend considerable time and money trying to fight this with your council).

Applying for a Lawful Development Certificate is a relatively straightforward and inexpensive process that could save you a lot of time, money and stress in the long run. Click the button below to find out more about it.


If you’re looking to construct a permitted development extension, its design will be led by the relevant permitted development rules. 

For example, the permitted development rules will tell you:

  • The maximum height of the extension
  • The maximum length/width of the extension
  • The position of the extension
  • The external materials of the extension which must be of similar appearance to the existing house’s external materials*.

*unless it is a conservatory.

As you can see, permitted development extensions don’t leave much scope to be creative with design or introduce bespoke features that are unique to your site.

For this reason, many homeowners choose to apply for planning permission instead. If you apply for planning permission for your domestic extension, your local council will assess it in detail. Planning permission will only be granted for your extension if it is considered to be a high quality built structure that causes no unacceptable impacts on neighbours or the local area.

domestic extensions

An exceptional, traditional design by heritage specialists, Julian Harrap Architects LLP. Planning Direct were pleased to assist with their successful planning appeal.

We’ve listed below the key issues that any local council will consider when assessing a planning application for a domestic extension. You can significantly increase your chances of securing planning permission by taking these issues into account from the earliest stages of the design process.

If you require further assistance with design, we do offer a design guidance service. Click the button below to find out more.

Key issues


Is the extension designed and (to be) constructed to a high architectural standard? Does it use appropriate construction materials that are safe and long-lasting? If your extension has been designed by a professional planning consultancy or architectural firm, it should certainly comply with this minimum requirement.

Effect on local character & appearance

Does the extension “fit in” to the site and residential street/area? Does it look awkward or like it belongs somewhere else? Are there other examples of similar extensions already in the area? In sensitive and historic areas (e.g. Conservation Areas or the settings of listed buildings), greater weight will be given to this impact. 

Effect on neighbours

Does the extension lead to a clear loss of light, privacy or outlook to neighbouring properties? Does it cast large shadows over a neighbouring house or its gardens? Do its windows cause overlooking of formerly private parts of a neighbouring house or garden? Does it appear prominently in neighbours’ views where previously they looked over open space, such as a garden? Have neighbours objected?

Effect on living conditions

Does the extension preserve or enhance the house’s living conditions? For example, if the extension replaces a parking area and there is no other parking available to the house, it is likely to be refused. The same is true if the extension causes internal parts of the house to become very dark and gloomy. Most extensions will tend to improve living conditions as they typically offer more space and facilities to the house’s occupants.

Accordance with planning policy

Finally, is the extension in compliance with relevant national and local design-based planning policies? If the extension is of high quality, has a positive/neutral effect on local character and appearance, has a positive/neutral effect on neighbours and a positive/neutral effect on the site’s own living conditions, it is very likely that it complies with national and local design policies.

However, you should always check what national and local policies apply long before you start working on design. Some local councils have very detailed design policies that you must take into account. For example, some local policies specify a minimum separation distance between neighbouring properties. In these circumstances, if your domestic extension caused the separation distance between your house and its neighbour(s) to fall below minimum standards, it would not be likely to receive planning permission.


Certainly not, but it should be “in keeping”. Generally speaking, this means it should adopt an overall style that prevents it from looking as though it’s been “tacked-on” to the rest of the house. A good rule of thumb is that a casual passer-by should not be able to identify at a glance where the original house stops and the extension begins. 

What about contemporary design?

An exception to this general rule is where the existing house has an older or more traditional character and the extension adopts a contemporary style. This can be a very appropriate design solution, especially in the case of older buildings with heritage value. It is an approach supported by Historic England as it enables a building’s historic parts to be easily identified and, therefore, appreciated. It is also recognised that good quality 21st Century additions to historic sites add more interest and value for the benefit of future generations – we know today that sites displaying architecture from the 15th, 16th and 17th centuries, for example, have more value and interest than those built in one era only.

This does mean that contemporary design is held to a very high standard in historic locations. The expectation will be that it displays the absolute best of modern 21st Century architecture.

In spite of Historic England’s support, it’s also the case that contemporary design can still be controversial in certain parts of the country, including more rural areas with less well-funded planning and heritage departments.

If you’re considering adding a contemporary extension to an older property, you may wish to apply for your local council’s pre-application advice before you spend time and money preparing a detailed planning application. Click the button below to find out more about submitting an application for pre-application advice.

Planning Direct also offers its own version of pre-application advice. We call these planning assessments. Click the button below to find out what our planning assessments can offer you.


We offer a wide range of comprehensive planning services to assist you with your domestic extension.

Depending on what type of extension you’re after and where you are in the design/application process, we can help you with all of the following:

Permitted development extensions

  • Working out whether your site benefits from permitted development rights to construct domestic extensions
  • Working out what extensions you could construct using permitted development rights and whether any of these options meet your needs and desires
  • Preparing, submitting and managing a prior approval application for a permitted development larger rear extension
  • Preparing, submitting and managing a lawful development certificate application to formally confirm the lawfulness of your permitted development extension.

All other domestic extensions

  • We can help you with all parts of the design process, including:
    • identification of all relevant national and local design policies to ensure compliance with their requirements
    • two-way discussion of your design requirements and priorities so that we can identify any potential conflicts with planning policies and jointly agree on design compromises or solutions
    • preparation of comprehensive planning drawings.
  • Preparing, submitting and managing a householder planning application, to include preparation of comprehensive planning drawings and a written statement to explain how the design of the extension responds to local and national policy requirements. We will also act as your agent until a decision is reached, responding to any design concerns raised by the council or your neighbours along the way. For domestic extensions to listed buildings, we can also prepare, submit and manage your separate application for listed building consent.
  • Preparing, submitting and managing a planning appeal, to include preparation of a comprehensive written appeal statement. If you’ve recently had permission refused for a domestic extension, you may have grounds to appeal. There’s no fee to appeal a planning refusal and around 1 in 3 planning appeals are successful so it’s well worth thinking about! Click the button below to find out more about planning appeals, including the deadlines to submit an appeal and the benefits of appealing.

If you need assistance with your domestic extension, please get in touch using the button below. Our initial advice is always free of charge.

Back to top