Planning permission: a beginner's guide

Chartered surveyor Peter Richards explains how the planning process works – read on if you’re considering extending or converting your home

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Planning permission, also known as planning consent, is the formal permission from a local authority for the erection or alteration of a building, and it's something you'll almost certainly need if you're considering a major project. It is also required for a change of use of buildings or land. 

So, if you're building an extension or approaching a house renovation find out everything you need to know about planning permission.

Do you need planning permission?

Certain types of project don’t require express planning permission as they qualify under permitted development rights (PD). In recent years, the government has extended what is permissible under PD in a bid to speed up the planning process. As a general rule, PD rights cover minor extensions, demolition and certain changes of use, such as a loft, garage or cellar conversions. 

However, is always worth checking with your local council to find out what is likely to be accepted, and double checking the government planning portal to see restrictions. In a bid to speed up the planning process, the maximum size allowed for a single-storey extension has been doubled until 2019.

It means you can add an eight-metre extension to a detached house or a six-metre extension to a detached property without planning permission. While most houses have PD rights, flats and maisonettes do not, so planning permission is required. PD rights are also reduced in Conservation Areas, National Parks and Areas of Outstanding Natural Beauty, but not in the Green Belt.

Planning permission and permitted development infographic

Applying for a certificate of lawfulness

If you want to be completely certain your project is lawful, you can apply to your local authority for a certificate of lawful development. This proves that the development is legal, and can be important when you come to sell.

An application needs to be submitted to your local authority. The forms are typically the same across all local authorities and can be accessed, completed and uploaded via You will need to submit scaled plans of your proposal and a location plan based on an up-to-date ordnance survey map. Scroll to the end of this page to see a flow chart of the process.

What does planning permission cost?

Application fees vary depending on the nature of the application – you can use the government's planning portal to calculate costs. Welsh authorities have a different fee schedule, and applications for listed buildings or those Conservation Areas don’t incur a fee.

How to apply for planning permission

You’ll need permission for significant extension and remodelling projects, and you can apply either through your local authority or online through the Planning Portal. Follow our step by step guide to applying for planning permission.

How long will it take to get planning permission?

Local authorities will usually advise of a target determination date when validating your application. For small-scale projects, they normally aim for eight weeks from validation to decision.

How long does planning permission last?

As a general rule, and unless stated otherwise in the letter notifying you of the decision, three years. This means that you should start work within that three-year window, or you will need to re-apply. 

What if the planning application is turned down?

‘First, it’s important to try to understand exactly why the application was rejected,’ says Hugo Tugman. ‘The proposals may be largely acceptable, but simply contain a detail that the local authority can’t approve, in which case resubmitting a new application that has been amended accordingly should be enough to get the permission that you require.

‘It may, however, be that what you are proposing is fundamentally outside the planning policy or guidance the planners are working with. If that is the case, you really need to understand what these policies are and redesign so that your scheme falls within these parameters.

‘The third possibility is that you feel your scheme was within the policy guidance, but the planning department has made an unreasonable interpretation of the rules and refused it. In this final case it may well be worth going to an appeal, where an inspector (not local authority) makes an independent assessment of whether policy has been applied correctly and reasonably.’

Making changes to your extension design after approval

Changing your extension's design after your planning application has been accepted will require a retrospective amendment, or a new application all together. Avoid this by studying your plans in detail and have a physical or digital model created to help with visualisation.

If the changes are very slight, it is possible to apply for a 'non-material amendment', but significant changes, such as the extension's overall height or the position of upstairs windows, for example, would be judged as 'material', meaning planners would have to advertise your plans again, in which case you may need to submit a new application.

What are Section 106 agreements?

These are legal agreements that run alongside some planning applications. They allow local authorities to secure monetary contributions to offset the impact of the proposal or control restrictions on the planning consent being sought. Normally, Section 106 agreements are reserved for larger applications, however, some local authorities are now using them to secure affordable housing contributions for developments of single plots, so it’s worth checking the local policy.

Will a tree preservation order be a problem?

It would be advisable to contact the council to ascertain whether the tree has a preservation order on it. If you are in a Conservation Area, you will also need to get special consent.

Permitted development

Planning permission

Interior remodellingAltering a listed building
Single storey side and rear extensionsAltering the street-facing elevation
Loft conversionsDividing a property into two
Outbuidlings with max eaves height 2.5mExtending a home that has used its permitted development allocation
Decking under 30cm high off the groundRemodelling or extended on designated land, such as Conservation Areas or Areas of Outstanding National Beauty
PorchesExtending near boundaries
Garage conversions

Building a new house


The planning process

planning permission flowchart

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