Planning Permission for Extensions: London Homeowner Guide

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%.