Why Extend?
Beyond the obvious benefit of more space, a well-planned extension offers:
Enhanced Natural Light
Modern glazing can transform a dark interior, creating bright, welcoming living spaces.
Location Continuity
Stay in the neighbourhood you love while upgrading your footprint. Avoid the stress and costs of moving.
Capital Growth
In high-demand areas like London, even a small 15m² extension can add significant market value to your property.
1. Navigating the "How": Planning vs. Permitted Development
The most critical question is how you will secure legal approval. There are two primary routes:
Route A: Permitted Development (PD)
Parliament has granted specific rights that allow homeowners to extend without seeking full planning permission, provided they stick to strict criteria.
Example: Single Storey Rear Extensions
To qualify for PD, your project must typically meet:
- •Detached Houses: Extend no more than 4m beyond the rear wall (or 8m under the Prior Approval "Larger Home Extension" scheme).
- •Other Houses: Extend no more than 3m (or 6m under Prior Approval).
- •Height: Not exceed 4m in total height.
- •Footprint: The total area covered by extensions must not exceed 50% of the original "curtilage" (garden/land).
Expert Tip: PD rights are not universal. They often do not apply to flats or maisonettes, and some local councils use Article 4 Directions to remove these rights entirely. Always consult a planning expert—not just an architect—to confirm your eligibility.
Route B: Full Planning Permission
If your design exceeds PD limits, you must submit a formal application. Your local council will assess the proposal against their Local Plan policies, considering factors such as:
- •Impact on neighbouring properties (overlooking, loss of light, overbearing)
- •Design and appearance in relation to the existing property
- •Character of the surrounding area
- •Highway safety and parking considerations
2. Pre-Application Advice
Before submitting a full planning application, consider seeking pre-application advice from your local council. This involves:
Early Feedback
Get an indication of whether your proposal is likely to be acceptable before investing in detailed drawings.
Policy Guidance
Understand which planning policies will be most relevant to your application.
Design Amendments
Make changes to your design before submission, potentially saving time and money.
3. The Application Process
Once you're ready to proceed, the typical planning application process involves:
Prepare Your Documents
Drawings (existing and proposed), site plan, design and access statement, and any specialist reports required.
Submit Application
Applications are submitted via the Planning Portal along with the appropriate fee.
Consultation Period
Neighbours and consultees are notified. The standard determination period is 8 weeks for householder applications.
Decision
The council will either approve (with or without conditions), refuse, or request amendments.
4. Don't Forget Building Regulations
Planning permission and building regulations are separate approvals. While planning controls what you can build and where, building regulations ensure the work is carried out safely and to required standards. This covers:
- •Structural stability and foundations
- •Fire safety and means of escape
- •Insulation and energy efficiency
- •Drainage and waste disposal
- •Electrical and gas safety
Key Takeaways
- 1.Always verify your permitted development rights before assuming you don't need planning permission.
- 2.Consider pre-application advice for complex or borderline proposals.
- 3.Engage a planning consultant early—their expertise can save time and money.
- 4.Don't forget building regulations—they're separate from planning permission.
- 5.A Certificate of Lawfulness provides legal certainty for permitted development works.