When Can an Extension Be a Permitted Development?

In this blog, we’ll explain when an extension could be considered permitted development and when planning permission may be required.

Permitted Development Basics  

An extension can often be considered permitted development meaning planning permission is not required. However, there are some important caveats, to be aware of to avoid falling foul of the most common permitted development mistakes. Only houses have permitted development rights but not all houses have permitted development rights. Flats, maisonettes, and commercial properties always need planning permission. 

Planning Constraints  

Planning constraints such as conservation areas, listed buildings, world heritage sites, areas of outstanding natural beauty, article 4 directions or even living under a flight path may limit or remove your permitted development rights. Any previous developments even by a previous owner a long time ago may have used some, or all of your Permitted Development rights, meaning planning permission IS required. 

Planning policies are also ever-changing. Even if your extension is permitted development today, the council can impose new planning constraints that remove your permitted development rights at any time in the future. This could result in a breach of planning, and risk enforcement action. If an enforcement notice is issued and retrospective planning permission is refused you would need to demolish the extension and restore the property back to its original state. 

When Can An Extension Be Permitted Development? 

If your house has permitted development rights and there are no hidden constraints that removed your PD rights, your extension may not need planning permission if it meets ALL of the following:   

Single-Storey Rear Extensions

• For Single-Storey Rear Extensions, to a Detached House can extend up to 4 Metres from the Original Rear Wall, while Semi-Detached and Terraced Houses are limited to 3 Metres.
• The maximum height must not exceed 4 Metres, and if the Extension is within 2 Metres of a Boundary, the height must be reduced to 3 Metres.
• The Width cannot be greater than the Existing House, and the Total Footprint of Extensions and Outbuildings must not cover more than 50% of the Land Surrounding the Original House.
• The Materials used must be similar to those of the Existing House

Two-Storey Rear Extensions

• Two-Storey Rear Extensions can extend a Maximum of 3 metres beyond the Original Rear Wall, provided they are at least 7 metres away from the Rear Boundary.
• The Height must not exceed the Existing House, and the Roof Pitch must match the Original Roof.
• Side-Facing Windows must be Obscure Glazed to maintain privacy.
• The Total Footprint of all Extensions and Outbuildings must not exceed 50% of the Total Land around the Original House.
• The Materials used must be similar to those of the Existing House.

Side Extensions

• For Side Extensions, only Single-Storey Developments are permitted under PD Rights.
  The Maximum Width allowed is 50% of the Width of the Original House, and the Maximum Height is 4 Metres.
• If the Extension is within 2 Metres of a Boundary, the Height must be limited to 3 Metres.
• The Total Footprint of all Extensions and Outbuildings must not exceed 50% of the Total Land around the Original House.
• The Materials used must be similar to those of the Existing House.

Front Extensions

Front Extensions are generally not permitted under PD rights, except for Small Porches.

Wraparound Extension

A Wraparound Extension does not fall within Permitted Development and requires full Planning Permission.

However, even if your extension meets these criteria, you may still need planning permission. 

For example, if there are hidden planning constraints or your permitted development rights have been used up by previous developments. 

It is important to note that 20% of our planning applications are retrospective and 99% of these were sure they didn’t need planning permission but got it wrong. 

 With this in mind, it’s best to check with your local planning authority or a chartered town planner before commencing work to limit your risk and expense. 

How to Find Out If You Need Planning Permission?

To find out if you need planning permission you have 2 options. 

The first option is to submit a pre-application to your council.  

This requires architectural drawings showing the property before and after the works, along with a detailed proposal explaining your plans and how they meet the relevant planning policies.  A pre-app costs up to £600 and typically takes 5 to 8 weeks for a response, though it’s not a legal determination and doesn’t guarantee approval. 
 
Alternatively, our town planners can provide a planning appraisal.   

We check the same planning policies, planning history, and planning constraints as the council but without the need for architectural drawings or a detailed proposal. The advantage of a planning appraisal is you’ll get the answers you need within a day instead of waiting weeks. 

A Lawful Development Certificate  

For anything likely to be considered Permitted Development it is always recommended to obtain a Lawful Development Certificate before commencing any works. A Lawful Development Certificate is the only way to prove that your development is Permitted Development and does not need planning permission.

It is also often required when selling or remortgaging your property, to prove to buyers or lenders that all modifications are lawful. Without planning permission or a lawful development certificate your extension may not increase the value of your property. By securing a Lawful Development Certificate, you’re investing in both the future security and potential value of your property.

If you’re considering building an extension and would like any help or advice contact us for a free no-obligation consultation.