Wondering whether you need planning permission for a home extension?
You’re not alone — it’s one of the most common questions we hear from homeowners.
At Fluent Architectural Design Services, we design hundreds of rear and side extensions every year, and the rules can seem confusing at first. The good news? Our expert team will help you make sense of it all — quickly and clearly — during our free on-site consultation and planning assessment, so you’ll know exactly what’s achievable before you commit to anything.
Here’s a straightforward guide to help you understand what’s allowed under permitted development and how we can support you at every step.
Rear Extensions
If your property benefits from permitted development rights, you can usually build a rear extension without applying for full planning permission.
Under Permitted Development:
- Terraced and semi-detached homes: You can extend up to 3 metres from the rear wall.
- Detached homes: You can extend up to 4 metres in depth.
Under Prior Approval (Larger Home Extension Scheme):
These limits can increase to:
- 6 metres for terraced or semi-detached houses
- 8 metres for detached houses
This process — known as a Prior Approval application — is something our in-house planning consultants manage from start to finish. We prepare the drawings, complete the paperwork, liaise with your local council and handle all communication, so everything runs smoothly from day one.
Side Extensions
Side extensions can also fall under permitted development, provided they stay within certain limits.
You can typically extend:
- Up to 50% of the width of your existing house
- Along the full depth of your home
For example, if your property is 7m wide, you could build a 3.5m wide side extension. You can even extend slightly beyond the rear wall too, following the same depth limits as a rear extension — just not as a wraparound.
The same height rules apply, and our experienced designers will ensure your new space looks balanced, practical, and in keeping with your home’s character.
