- December 17, 2025
- 8:24 pm
Do I Need Planning Permission for My Home Extension?
One of the first questions Hertfordshire homeowners ask when considering more space is “Do I need planning permission for an extension?” The answer isn’t always straightforward, but understanding the basics early saves time, money and stress. Our council planning approval service guides you through the rules—from permitted development assessments to full planning applications—so you can move forward with confidence and clarity.
Table of Contents
Permitted Development Rights Explained
Many single-storey rear extensions fall under Permitted Development (PD) rights, meaning no full planning application is required.
Key current limits (England 2025):
- Detached house: up to 8 metres projection (or 6 metres without Prior Approval)
- Semi-detached/terrace: up to 6 metres (or 3 metres without Prior Approval)
- Maximum height 4 metres, eaves 3 metres
These rights are generous for many homeowners – but local restrictions can remove them completely.
When You Definitely Need Full Planning Permission
Certain situations always require a full application:
- Two-storey extensions
- Side extensions over half the width of the original house
- Front extensions
- Properties in Conservation Areas, Green Belt or Listed Buildings (PD rights often removed)
- Extensions exceeding PD volume limits
Common Misconceptions About Extensions
Myths cause expensive mistakes:
- “If my neighbour got permission, I will too” – each case is assessed individually
- “PD rights are the same everywhere” – many Hertfordshire councils have Article 4 directions removing them
- “I can build first and apply later” – enforcement action is real and costly
For example, our Enfield home extension projects often encounter Article 4 directions that remove standard permitted development rights, meaning extensions that would be automatic elsewhere require full planning applications. Understanding your property’s specific planning context from the start avoids costly surprises.
Thinking about extending your home? Want to understand if you need Council Approval?
How Location Affects Your Planning Requirements
Hertfordshire councils vary in approach:
- St Albans – large conservation areas, many Article 4 directions
- Watford & Hemel Hempstead – generally more permissive
- Green Belt properties – stricter volume and visual impact rules
Early professional advice identifies your specific constraints.
The Prior Approval Process for Larger Extensions
The Larger Home Extension scheme allows bigger single-storey rear extensions (up to 8 m detached, 6 m attached) with a simplified Prior Approval application to the council.
Benefits:
- Faster than full planning
- Neighbour consultation handled by council
Still requires professional drawings and compliance checks.
What Happens If You Build Without Permission
Building without required permission risks:
- Enforcement notice and removal order
- Difficulty selling the property (no indemnity insurance)
- Fines and legal costs
Professional guidance from the start eliminates this risk.
Why Professional Guidance Makes All the Difference
Our 100% approval rate comes from:
- Deep knowledge of local council preferences
- Proactive pre-application advice where needed
- Detailed, compliant submissions first time
We turn planning uncertainty into certainty.
Checklist: Do You Need Planning Permission?
- Is your extension single-storey rear only?
- Does it stay within PD size limits?
- Is your property in a Conservation Area/Listed/Green Belt?
- Has your council removed PD rights via Article 4?
- Are you adding a second storey or front extension?
If unsure on any point – book a free consultation for clarity.
Expert Insights
- “Most planning refusals stem from avoidable design issues – fixed easily with early professional input.”
- “Prior Approval is often faster and cheaper than full planning when eligible.”
- “Neighbour consultation doesn’t mean neighbour approval – councils make the decision.”
Michelle Dunbar (Director & Senior Project Manager)
Michelle oversees the day-to-day operations, manages client relationships, and ensures each project is delivered to a consistent, professional standard.
Step-by-step guide to planning a home extension: feasibility, design, planning approval & build….read more
What happens during the build phase of your home extension? Clear timelines, key stages and coordination….read more
Discover what makes a home extension successful – from early planning and design coordination to build….read more
Frequently Asked Questions
Do all home extensions need planning permission?
No – many single-storey rear extensions fall under Permitted Development rights and require no full application, though local restrictions can change this.
How big can my extension be without planning permission?
For detached houses: up to 8 metres projection (Prior Approval) or 6 metres (standard PD). For semi-detached/terraced: 6 metres (Prior Approval) or 3 metres (standard PD). Height and other limits apply.
What if my house is in a Conservation Area?
Permitted Development rights are usually removed, meaning full planning permission is required even for modest extensions.
Can I extend under permitted development in Hertfordshire Green Belt?
PD rights are often restricted in Green Belt areas, requiring full permission even for small extensions. Specialist advice helps navigate volume limits and visual impact rules for successful outcomes.
Can I build first and apply for permission later?
No – this is retrospective planning and carries significant risk of refusal and enforcement action. Always check first.
Will my neighbours be able to stop my extension?
Neighbours are consulted but cannot veto a compliant proposal. Councils decide based on policy.
What happens if my home extension violates planning rules?
Councils may issue enforcement notices requiring changes or removal, with potential fines up to £20,000. Professional compliance checks from the start prevent these risks and ensure saleable properties.
How long does planning permission take in Hertfordshire?
Standard householder applications: 8 weeks statutory, often 8-12 weeks in practice. Prior Approval: 42 days neighbour consultation + decision.
Ready to Check Your Extension’s Planning Requirements?
Home Extension Design
Turning ideas into plans that work
Council Planning Approval
Navigating applications with 100% success
Build Project Management
Delivering every detail to completion