How does Planning Permission work?

Some extensions do not require permission and may be built under a term called Permitted Development (PD). PD means that your building works meet a specific set of criteria, and are allowed to proceed without any formal permissions.

If you do need Planning Permission, the process works like this:

  1. Create a plan for your build; this usually requires help from a designer or architect.
  2. Completion of the application forms, either through an online portal or via paper copy.
  3. Submission of your application, usually 5 x copies, to the local authority for consideration along with the fee and other documentation.

What other documents do I need to submit with a Planning Application?

You will usually be required to submit several supporting documents along with your plans, completed application forms and the fee. These include:

  • A certificate of ownership to prove that the applicant owns the property in question.
  • A Design and Access Statement – this outlines the design concept and how the site will be accessed.
  • Plans showing the whole site, the elevations of the existing property and proposed build, and a block plan.

How long does Planning Permission take?

Simple applications are usually approved within eight weeks. However, if your plans are complex or there are other issues to consider, it may take considerably longer.

Whilst the application is being considered you will be required to display a public notice outside the property. This is part of the public consultation process and needs to be available for three to eight weeks to allow any objections to be raised.


When does Permitted Development apply?

If your extension meets the PD rules, you will not need to apply for Planning Permission. It is always advisable to verify that your extension falls within the PD criteria with your local authority before building work begins.

Permitted Development criteria for single-storey extensions

  • The extension is not on Designated Land – for example, in a conservation area, being a Listed Building or in an Area of Outstanding Natural Beauty.
  • No more than 50% of the original land around the property will be built on – this includes any previous extension builds.
  • If the extension is to the front of the house, it must not be fronting a highway or public road
  • The materials in the extension design are consistent with the existing property.
  • For side extensions, the width of the extension must not be wider than 50% of the original property width.
  • Side extensions must be no higher than four metres, and no more than 50% of the height of the original property.
  • Should the extension finish within two metres of a boundary, the maximum height must not exceed three metres.
  • A rear extension cannot extend back beyond the existing property by more than three metres for a semi-detached or terraced house, and four metres for a detached home.
  • The maximum permissible height of a single-story rear extension under PD is four metres. Get small extension cost quotes here.

Frequently Asked Questions

Can Permitted Development rights be withdrawn?

Whilst unusual, a local authority can issue a directive called ‘Article 4’ that removes a homeowners right to build under PD.

This is not common and is usually a way to prevent a build taking place that technically falls within the PD criteria but would threaten the character or aesthetic of an important area, such as a conservation area.

Given this possibility, it is even more important to seek verification from your local authority that PD does apply to avoid any potential issues during your extension build.

What is a Lawful Development Certificate?

A Lawful Development Certificate is not mandatory but acts as formal confirmation that your extension did not require Planning Permission, and was correctly built under PD.

This can be very useful should any future queries arise, particularly when planning to sell your home.
This certificate is issued by the Planning Portal service through your local authority, and costs half of the normal price of a Planning Permission application at £103.

If your application for a Lawful Development Certificate is refused, this is normally because insufficient information was included within the application for the certification to be granted. You can also appeal against a rejected application if your request is turned down, the certificate doesn’t match what you have applied for, or you have not received a response within eight weeks.

What happens if I needed Planning Permission but did not apply?

The consequences of failing to obtain permission before a build can be serious. This means it is very worthwhile taking a little extra time to plan your extension before the work begins.

When this happens it is called a Planning Breach and is normally because the homeowner never applied for permission, or was rejected and continued with their build regardless.

A breach can also occur when permission has been granted but the build has not been consistent with the original designs submitted.

What are the consequences of a Planning Breach?

The consequences can include:

  • Retrospective planning – sometimes, the authority is prepared to grant retrospective permission, usually where there is a justifiable reason where permission was not applied for, or where PD could have been assumed to apply.
  • An enforcement order can be issued, which often means you need to take down the extension and return the property to its previous condition.
  • Prosecution – if an enforcement notice is issued and an appeal is rejected, there is a possibility of prosecution if you refuse to comply.

As you can see, the costs and time delays incurred with a Planning Breach can be serious, so investing time in creating professional designs and completing the application process is the best option in the long-term.

Mike Alexander
Hey there, I'm Mike - writer and part time home improvement expert at Refurbb. Since owning and refurbishing my own property in 2018, I've since been developing rental properties, writing about my home improvement endeavours, sharing what I've learned and connecting readers to reputable tradespeople in the UK.

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