Planning consent for your extension

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Planning Consent

Planning consent is one of the first concerns on everybody check list.  Increasing the size of your home is a great way to add value and much-needed space.  Your neighbours and local planning may not always look at it in the same way!

With the cost of moving today, extending your home is a great way to obtain your desired living space.  A property that has the potential to be transformed might be a better solution than finding a building plot.  It may also be easier than getting permission to knock down and rebuild.

Whether you need planning consent to carry out your development or not will vary from case to case.  This will be dependent on a number of factors.  In this article we take a look at what does and doesn’t need planning consent.  Also, overarching planning policies on new extensions and the key considerations to ensure your project is a success.


Every kind of extension – one or two storeys; front, side or rear, modifications to the roof, a conservatory or simply a porch, requires planning consent.  You may already have this permission under the rules of Permitted Development (PD). PD is subject to an enormous amount of criteria.  In this area (Gloucestershire), PD rights can allow up to an 8m long, single-storey rear extension on detached houses.   On attached houses up to 6m is permitted.  You will still need to notify the local planning authority.  The local authority will then consult with your neighbours and look into the impact of your proposal if they end up objecting.  In other parts of the UK, the limits are 4m and 3m respectively.

Complex legislation

Permitted Development rights are not without their complexities. They are also not applicable in a range of circumstances.  The council can remove PD rights on an individual property or a whole area by means of an Article 4 Direction.  Also, they are not valid on flats or listed properties, and only apply to a building as it stood in 1948 or to the original structure, if built since then.  If your scheme could come under the permitted development bracket then it’s often wise to check with the council.  You can apply for a lawful development certificate (LDC).  This is similar to planning permission, but the authority can only answer saying ‘yes, it is permitted development’ or ‘no, it isn’t’.

Not within Permitted Development

If your scheme does not fit under PD then you’ll need to submit a full planning application.  Your local council will have a a number of policies in place to manage development in the region.  These will govern their decision about whether to approve your extension.  Local Plans will cover guidance for extensions, but the details are sometimes fleshed out in supplementary documents or design guides.  You might also find information in your Neighbourhood Plan, if there’s one covering your location.  If you’re in doubt about which policies apply to your project, it is always worth contacting your local planning department.

Planning Policy

The exact wording in these documents varies greatly from council to council, although there are common planning considerations that apply to all extensions.  Policies are usually more restrictive in the countryside than in settlements.  Councils might have specific policies that apply to extensions in greenbelt land, conversation areas and areas of outstanding natural beauty.  A key point to note is that in the countryside and protected areas, policies usually limit the scale of addition allowed.  Some use vague language – such as that the extension mustn’t be ‘disproportionate’ relative to the original dwelling.  Others (particularly older policies) might set a percentage floor area or volume limit.  If a measurable figure isn’t specified, it’s likely that the planning officers work to a rule of thumb percentage, so ask them what this is to save you some guesswork.

Space requirements

More detailed policies that are set out in supplementary guidance and design guides might specify minimum distances between buildings and particular angles of sight from neighbours’ windows that your extension should not break.  This policy more often affects Terraced houses and semis with close neighbours.

Policies for extensions to listed buildings are very restrictive.  Limitations might even apply if your property is positioned close to a listed building. Any nearby development could be deemed as affecting the setting.  Note that large extensions of over 100mmay be liable for Community Infrastructure Levy (CIL) payments.  However, if you’re going to live in the property for three years after completing the extension then you can claim for an exemption, as is the case with self-build projects.

Key Considerations

Planning consent policies often require extensions to blend with the character of the existing house and not dominate or overwhelm it.  The extension should not overly affect the front facade. To avoid this, aim to set your extension back slightly.  Further, position the extension lower than the existing ridge height.  There’s greater flexibility with rear additions. Policies typically point towards extensions blending in with the existing house in terms of design, materials and finishes.  Councils may view positively the addition of a contemporary extension to a traditional building, this approach could be the way forward.

Government guidance – set out in the National Planning Policy Framework (NPPF) – expresses caution against an overly prescriptive approach to design, but does lend support to the idea of promoting or reinforcing local distinctiveness.

Impact on neighbours

Another key planning consideration for planning consent is an extension’s impact on neighbours.  Avoid creating a loss of light or outlook for them.  Avoid any reduction in their (or your own) privacy from overlooking windows or gardens.  Ideally, show them your plans before you apply and look to seek their support for your application.  However, be aware that if your neighbours don’t object simply because you’re best friends, the council won’t automatically follow suit.  Extensions can impact on trees (both on your land and potentially even next door) so if you’re looking to build close to these you’ll need to include a tree survey and statement as part of your application.  Impact on greenery that forms a part of the street scene can be a particularly sensitive issue.

European Protected species such as Great crested newts will affect your application. The law protects the animals and their eggs, breeding sites and resting places.  Obtain an ecological survey in these cases.  While the presence of sewers and drains isn’t a planning issue, they could influence house layout and/or the cost.

Planning Tactics

When you put in your application, it pays to consider what you could do as permitted development.   Present this as part of the case in favour of your scheme.  Some people obtain a certificate of lawfulness for the biggest, ugliest extension they could achieve under permitted development. They will then point out that if formal planning permission isn’t forthcoming they’ll build that instead.   This approach can be particularly useful in green belt. Here PD can sometimes enable a larger extension than the policy would normally allow.  Maximise the size of your extension you could get permission for something you think the council will be happy with.  Once you have permission you can apply to enlarge it.  The council would have to demonstrate the negative impact that a further 300mm would have.

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