How to Get Planning Permission for a Home Extension in London (2026 Step-by-Step Guide)
The planning process for a London home extension is more straightforward than most homeowners expect. This guide covers every step, from confirming whether you need permission at all through to the council's decision - with the costs and timelines at each stage.
TL;DR - The Quick Answer
Getting planning permission for a London home extension involves seven steps: confirming you need it (vs permitted development), appointing an architect, preparing drawings, submitting the application (council fee: £258), neighbour consultation, the 8-week decision period, and addressing any conditions on approval. Most standard rear extensions are approved. The most common refusal reasons - excessive scale, overlooking, design quality - are avoidable with good drawings and professional planning input.
Step 0: Do You Even Need Planning Permission?
Before starting the planning process, confirm whether your extension needs permission. Many London extensions qualify as permitted development - meaning no planning permission is required.
| Extension Type | PD Limit | Planning Needed If Over Limit |
|---|---|---|
| Rear extension (detached) | Up to 4m deep, single storey | Yes |
| Rear extension (semi/terrace) | Up to 3m deep, single storey | Yes (or prior approval 3–6m) |
| Side extension | Up to half original house width | Yes |
| Loft conversion (hip-to-gable) | Up to 40m3 additional volume | Yes |
| Two-storey extension | Not PD - always needs permission | Always required |
| Front extension | Not PD - always needs permission | Always required |
Important: Article 4 Directions in London
Many London streets have Article 4 Directions that remove permitted development rights - even for extensions that would normally qualify. This is common in conservation areas but also affects some non-conservation streets in inner London. Always confirm your Article 4 status before assuming your project is permitted development. Mayfair Studio's free AI check identifies Article 4 directions automatically.
The 7-Step Planning Process
Pre-application enquiry (optional)
For complex projects or sensitive locations, you can ask your council informally whether they would support your proposed extension before submitting a formal application. Most standard rear extensions do not need this - proceed directly to appointing an architect. Pre-apps are most useful for two-storey additions, conservation area extensions, or if a previous application was refused.
Appoint an architect
Appoint a fixed-fee architectural service or local RIBA practice. At Mayfair Studio, the process starts with a free AI property check - confirming permitted development status, conservation area constraints, and planning history - before you commit to any fee.
Site survey and design
Your architect surveys the property (measuring existing rooms and elevations) and prepares a design proposal based on your brief. You review and approve the design before drawings are finalised. Allow one or two revision rounds at this stage.
Planning drawings prepared
The architect prepares the formal planning drawings pack: site location plan (1:1250), site plan (1:500), existing and proposed floor plans (1:50 or 1:100), and existing and proposed elevations. A design and access statement is written. These are submitted via the Planning Portal.
Application submitted and validated
Your architect submits the application via the Planning Portal with the required documents and the £258 fee. The council validates the application - checking all required documents are present. Once validated, the 8-week decision clock starts.
Neighbour consultation and case officer review
The council notifies your immediate neighbours (typically by letter) and posts a site notice. Neighbours have 21 days to comment. Your case officer reviews the application against local planning policy. Your architect may receive requests for clarification or minor amendments - these are handled as part of the service at Mayfair Studio.
Decision issued
The council issues a decision notice: approval, approval with conditions, or refusal. Most householder applications are approved. If approved with conditions (common for materials or landscaping), you must comply with those conditions before or during construction. If refused, you can resubmit within 12 months at no extra council fee.
Planning Permission Timeline
| Week | Milestone | Who Does It |
|---|---|---|
| Week 1 | AI property check + appoint architect | You + Mayfair Studio |
| Weeks 1–2 | Site survey and measured drawings | Architect |
| Weeks 2–4 | Design development and revisions | Architect + you |
| Weeks 4–5 | Planning drawings finalised | Architect |
| Week 5–6 | Application submitted, council fee paid (£258) | Architect + you |
| Week 6–7 | Application validated by council | Council |
| Weeks 7–9 | Neighbour consultation (21-day period) | Council |
| Weeks 9–14 | Case officer review and decision | Council |
| Week 14–18 | Decision notice issued (approval/refusal) | Council |
Common Refusal Reasons and How to Avoid Them
Excessive scale or bulk
How to avoid it: Keep the extension proportionate to the original house. Single-storey extensions should not exceed 50% of the original rear garden. Eave and ridge heights should not exceed the original building.
Loss of amenity - overlooking or overshadowing
How to avoid it: Position and orientate windows to avoid direct overlooking of neighbours' gardens. Apply the 45-degree rule to ensure your extension doesn't significantly shadow a neighbour's main habitable rooms.
Out of character with the street scene
How to avoid it: Match materials to the original house and surrounding properties. In conservation areas, brick matching and traditional details are scrutinised. Avoid dramatically contemporary roof forms where the context is traditional.
Insufficient garden space remaining
How to avoid it: Many London boroughs have minimum garden area policies. Check your borough's local plan for garden land policies before designing an extension that would leave less than 50m2 of usable garden.
Total Planning Cost Summary
| Item | Cost | Notes |
|---|---|---|
| Architect drawings + application (Mayfair Studio) | From £1,295 | Fixed fee, planning drawings + submission |
| Council planning application fee | £258 | Paid to council directly (householder application) |
| Pre-application enquiry (if needed) | £100–£400 | Optional, council fee, not always needed |
| Building regulations drawings (after approval) | £1,500–£2,500 | Separate service, commissioned post-approval |
| Structural engineering | £600–£1,500 | Required for most extensions with beams |
| Total (planning stage) | ~£1,553 | Architect fee + council fee only |
| Step | Action | Timeline | Cost |
|---|---|---|---|
| 1 | Confirm PD or appoint architect | Week 1 | Free / from £1,295 |
| 2–3 | Site survey and design development | Weeks 1–4 | Included in architect fee |
| 4–5 | Planning drawings prepared and submitted | Weeks 4–6 | £258 council fee |
| 6–7 | Application validated by council | Weeks 6–7 | None |
| 7–14 | Neighbour consultation and case officer review | Weeks 7–14 | None |
| 14–18 | Decision notice issued | Week 14–18 | None |
Source: Mayfair Studio project data • Data as of 2026
Official Resources
- Planning Portal - submit planning applications, check permitted development, find your local planning authority
- GOV.UK: Planning permission in England - official guidance on when permission is required and how to apply
- GPDO Schedule 2 Part 1 - Permitted Development Rights - the legislation governing what householders can build without planning permission
Getting planning permission for a London extension takes 8 weeks minimum from validation, with the full process running 14 to 18 weeks from appointing an architect. The council application fee is £258 for a householder application. Common refusal reasons are excessive scale, overlooking, and design out of character. Approval rates for standard rear extensions are high when drawings are professionally prepared.
Frequently Asked Questions
How long does planning permission take for a home extension in London?
A standard householder planning application in London has a statutory 8-week decision period from the date the application is validated. However, validation itself can take 1–2 weeks after submission, and some councils take longer than 8 weeks in practice - particularly inner London boroughs with high caseloads. Allow 10–12 weeks from submission to decision. Add 4–6 weeks for drawing preparation before that, making a typical total of 14–18 weeks from appointing an architect to having planning permission.
What happens if my planning application is refused?
You have three options after a refusal: (1) Submit a revised application addressing the council's specific reasons for refusal - no fee for a resubmission within 12 months of the original decision; (2) Appeal to the Planning Inspectorate - free but typically takes 6–12 months; (3) Appoint a planning consultant to negotiate with the council before resubmitting. In London, most residential applications that are refused can be resubmitted successfully with relatively minor design changes.
Can I start building before planning permission is granted?
No. Building before planning permission is granted constitutes a planning breach. Enforcement action can require you to demolish the extension at your own cost. The only exception is permitted development - if your project genuinely qualifies as permitted development, you can build without planning permission. Confirm PD status via an AI check or by obtaining a Lawful Development Certificate before starting.
What is a pre-application enquiry and do I need one?
A pre-application enquiry lets you ask your council whether they would support a proposed development before you submit a formal application. Most London councils charge £100–£400 for a written pre-app response. They are most useful for: projects in sensitive locations (conservation areas, near listed buildings), two-storey extensions, or any project where you are uncertain about policy compliance. For a standard rear extension on a non-sensitive site, a pre-app is usually unnecessary.
How much does a planning application cost in London?
The council fee for a householder planning application in England is currently £258 (as of 2026). This is paid to the council directly. In addition, you need planning drawings and an application service - Mayfair Studio charges £1,295 for drawings and application management. Total cost for a standard London planning application: approximately £1,550 (council fee plus architect drawings and submission).
What are the most common reasons planning permission is refused for extensions in London?
The five most common refusal reasons for residential extensions in London are: (1) Excessive scale - extension too large relative to the original house or plot; (2) Loss of amenity - overlooking, overshadowing, or loss of daylight to neighbours; (3) Design quality - extension out of character with the area or the original building; (4) Loss of garden space - particularly in boroughs with garden land policies; (5) Conservation area harm - design, materials, or scale inappropriate in a conservation area. A good architectural service will identify these risks before submission.
What is the neighbour consultation scheme for permitted development?
The neighbour consultation scheme (also called prior approval or the larger home extension scheme) allows single-storey rear extensions up to 8m deep (detached houses) or 6m deep (semi-detached and terraced houses) under permitted development, subject to neighbour consultation. Your council notifies adjoining neighbours, who have 21 days to raise objections. If no objections are raised (or raised objections are not material), the council issues prior approval. This is faster than full planning permission - 42-day decision period instead of 8 weeks.
Getting planning permission for a home extension in London: appoint an architect to prepare drawings (Mayfair Studio from £1,295), submit a householder planning application online via Planning Portal with drawings and application fee (£258), wait 8–12 weeks for council determination. Most straightforward householder applications are approved. Conservation area applications may take 10–13 weeks and require heritage-appropriate designs. Mayfair Studio handles the full application as part of its fixed fee.
Frequently Asked Questions
How do I get planning permission for a home extension in London?
To get planning permission for a home extension in London: (1) Appoint an architect to prepare planning drawings - Mayfair Studio from £1,295. (2) Submit a householder planning application online via the Planning Portal with drawings, site plan, and fee (£258). (3) Local authority validates and consults neighbours - 8–12 week determination period. (4) Receive planning permission with conditions. (5) Discharge any pre-commencement conditions before starting. Mayfair Studio handles the full application as part of its fixed fee.
How much does planning permission cost for a home extension in London?
Planning permission fees in London: householder application (standard extensions) £258; full planning application (larger or more complex projects) £578. These are government fees paid directly to the council. Additional costs: architect fees from £1,295 (Mayfair Studio, includes application preparation); building regulations approval £800–£2,000. Total planning process cost including architect: £1,600–£4,500 for most residential extensions.
How long does it take to get planning permission for a home extension in London?
Planning permission for a home extension in London takes 8 weeks from valid application submission (the statutory determination period). Conservation area applications may take 10–13 weeks. Pre-application advice (optional but recommended in complex cases) adds 4–8 weeks before submission. With design time included: allow 3–5 months from appointing an architect to receiving planning permission. Mayfair Studio's design phase typically takes 4–8 weeks before planning submission.
What are the chances of getting planning permission for a home extension in London?
Planning approval rates for householder extensions in London vary by borough: outer boroughs (Brent, Tower Hamlets, Greenwich) approve around 78–80% of applications. Inner boroughs (Hackney, Islington) approve around 68–74%. Conservation area-heavy boroughs (Camden, Kensington & Chelsea) approve around 55–65%. Well-designed applications that follow local design guidance and conservation area requirements are approved at much higher rates - Mayfair Studio's track record across London boroughs is strong.
Can I extend my house without planning permission in London?
Yes - many extensions qualify as permitted development (PD) and don't need planning permission: single-storey rear extensions up to 3m deep (terraced/semi) or 4m deep (detached), loft conversions under 40m³ (terraced) or 50m³ (detached/semi). However, conservation areas, Article 4 directions, and listed buildings remove PD rights. Always check your specific address before assuming PD applies - Mayfair Studio's free AI chat checks your property's PD status instantly.