Understanding planning permission is crucial for any London home extension project. This comprehensive guide explains when you need it, how to apply, and how to maximize your chances of approval.
Do You Need Planning Permission?
Permitted Development Rights
Many extensions can proceed under Permitted Development (PD) without full planning permission. For single-storey rear extensions, PD allows:
Terraced & Semi-Detached Houses:
- Up to 3m extension beyond the original rear wall
- Up to 6m with neighbor consultation scheme
- Maximum height 4m, eaves height 3m
- Maximum 50% garden coverage
Detached Houses:
- Up to 4m extension beyond original rear wall
- Up to 8m with neighbor consultation scheme
- Same height restrictions as above
When PD Doesn’t Apply
You WILL need planning permission if:
- Property is listed or in a conservation area
- Extension exceeds PD limits
- Previous extensions used up PD allowance
- House is a flat or maisonette
- You’re extending beyond the side elevation
- Building more than 50% garden coverage
The Planning Application Process
Step 1: Pre-Application Advice (Optional but Recommended)
Most London councils offer pre-application consultations (£100-£300). A planning officer reviews your proposal informally and provides feedback. This can save thousands if there are issues.
Step 2: Prepare Your Application
You’ll need:
- Site location plan (1:1250 or 1:2500 scale)
- Block plan (showing boundaries) 1:500 or 1:200
- Existing and proposed elevations
- Existing and proposed floor plans
- Application form
- Fee (£206 for householder applications)
Step 3: Submit Application
Applications can be submitted via the Planning Portal online. Your council has 8 weeks to decide (or 13 weeks for major applications).
Step 4: Consultation Period
Your neighbors will be notified (21-day consultation period). If they object, explain your design rationale. Many objections stem from misunderstandings.
Step 5: Decision
The council will either:
- Approve: You can proceed (subject to conditions)
- Refuse: You can revise and resubmit, or appeal
- Request amendments: Make changes and resubmit
Maximizing Approval Chances
Design Quality
London councils prioritize design quality. Your extension should:
- Use sympathetic materials matching existing property
- Respect the street scene and neighboring properties
- Not significantly reduce neighbors’ light or privacy
- Be proportionate to the original building
Common Rejection Reasons
- Overdevelopment: Extension too large for plot
- Overlooking: Windows facing directly into neighbors
- Poor design: Unsympathetic materials or proportions
- Loss of light: Significantly affecting neighbors
- Out of character: Doesn’t match conservation area
Conservation Areas
22% of London is in conservation areas. Additional restrictions apply:
- Side extensions NO LONGER permitted development
- Cladding/render requires permission
- Roof alterations need permission
- Much stricter material requirements
Article 4 Directions
Some conservation areas have Article 4 Directions removing many PD rights entirely. Check your local council’s planning portal.
If Your Application Is Refused
Option 1: Revise and Resubmit
Address the council’s concerns and submit a new application. There’s no fee if resubmitted within 12 months.
Option 2: Appeal
You have 6 months to appeal to the Planning Inspectorate. Appeals cost £1,000-5,000 in professional fees and take 6-8 months. Success rate is approximately 33%.
Costs Summary
- DIY application: £206 (fee only)
- Architectural drawings: £800-£2,000
- Planning consultant: £1,500-£3,500
- Full service (architect handling all): £2,500-£5,000
Building Regulations
Separate from planning permission, Building Regulations ensure structural safety. You’ll need Building Control approval for:
- All structural changes
- New drainage
- Electrical work
- Insulation standards
Building Control fees: £800-£1,500 (council) or £600-£1,200 (private inspector).
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