Do I Need Planning Permission for My Extension?
do-i-need-planning-permission-for-my-extension
Not all extensions need planning permission. Learn how Permitted Development works, when you’ll need full permission, and why a Certificate of Lawfulness is worth getting.
If you’re planning a home extension, one of the first questions that comes up is: “Do I need planning permission for this?” The answer is... it depends.
In this article, we’ll walk you through what does and doesn’t need permission, what Permitted Development actually means, and the one document we always recommend applying for, even if full planning isn’t required.
UNDERSTANDING PERMITTED DEVELOPMENT
Some smaller home extensions don’t need planning permission because they fall under Permitted Development Rights. These are national rules that allow certain types of work without the need for a full planning application.
To qualify, your project needs to meet very specific limits and conditions. These cover things like:
• The overall size and height of the extension
• Where it sits in relation to your existing home
• The distance from boundaries
• How much garden space is retained
• The materials used
For example: A single-storey rear extension on a typical semi-detached house might not need planning, as long as it doesn’t project more than 3 metres from the rear wall and stays within height limits.
WHEN PERMITTED DEVELOPMENT DOESN’T APPLY
Even if your extension is quite modest, you’ll still need Householder Planning Permission if:
• Your home is in a Conservation Area, National Park, or Area of Outstanding Natural Beauty (AONB)
• You’re extending to the side, adding height, or wrapping around corners
• You’re planning a two-storey extension, large loft conversion, or significant alterations to the roof
• You want to build a new annexe, detached structure, or change the use of the space
And if your property has already been extended in the past, you may have used up some of your Permitted Development rights.
WHAT IS A CERTIFICATE OF LAWFULNESS?
Even if your project qualifies as Permitted Development, we strongly recommend applying for a Certificate of Lawfulness before you begin.
This is a formal document from the council confirming that your extension meets the rules. It’s not the same as planning permission, but it gives you legal certainty – and it can be a lifesaver when selling your home.
We’ve seen cases where a project was technically permitted, but the lack of a certificate caused delays and triggered legal wrangling during a house sale. It’s not worth the risk.
THE PLANNING ROUTE WE RECOMMEND MOST
As a practice, we always start with a site-specific review to advise whether full permission is needed. If there’s any doubt, we’ll often suggest a Certificate of Lawfulness application as the safest way forward.
In many cases, we’ll draw up your extension plans to meet PD rules where possible, but we’ll also talk through the trade-offs. Sometimes the flexibility and long-term value of a full planning application are worth the extra time and fee.
REAL-WORLD EXAMPLES
A recent client in a Conservation Area wanted to extend 2.5 metres to the rear. Even though the size was modest, we needed to go through a Householder Planning Application because the area had additional restrictions.
Another client had a detached 1970s bungalow outside any designated area. We were able to add a generous rear extension with rooflights and large glazed doors – all under Permitted Development, with a Certificate of Lawfulness to back it up.
COMMON PLANNING MISCONCEPTIONS
• “It’s at the back of the house, so it’s fine.”
Not always. Rear extensions still need to meet size, height, and boundary limits.
• “My neighbour did something similar, so I can too.”
Maybe – but every house has a unique planning history. Rights can differ between properties.
• “If it’s internal work, I don’t need permission.”
Internal layout changes don’t need planning, but they may still need Building Regulations approval.
CLOSING THOUGHTS
Planning rules can be surprisingly complex, but with the right advice, they don’t need to be stressful. Whether your project needs planning permission or qualifies as Permitted Development, we’ll guide you through it step by step.
If you’re unsure what approvals your extension needs, get in touch and we’ll help you make a clear, confident start.