Wandsworth Extension Planning 2026: Rules, Costs & Guide
Complete guide to extending your home in Wandsworth. Planning permission requirements, basement policy, conservation area rules, and typical costs.
TL;DR - The Quick Answer
Most Wandsworth homes can extend under permitted development - single-storey rear extensions up to 3m (terraced and semi-detached) or 4m (detached) without planning permission. However, the borough has 76 conservation areas where additional restrictions apply, and all basement projects require full planning permission. Build costs run £1,900–2,700/m², with an 8-12% premium in conservation areas. Planning decisions typically take 8–13 weeks. Multi-level basements are not permitted anywhere in the borough.
Planning Permission in Wandsworth
Wandsworth is London's largest borough by population, with 76 conservation areas covering areas like Battersea, Clapham, Putney, and Wandsworth Town. This means many properties have additional planning restrictions beyond standard permitted development rights.
The Wandsworth Housing SPD provides detailed guidance for rear extensions, basements, and roof extensions. Check your property against planning constraints before starting any design work.
Permitted Development Rights
Standard permitted development rules apply in most of Wandsworth, but conservation areas and Article 4 directions create exceptions:
| Extension Type | Max Without Permission | Wandsworth Notes |
|---|---|---|
| Single-storey rear (detached) | 4m deep, 4m high | Allowed outside conservation areas |
| Single-storey rear (semi/terrace) | 3m deep, 4m high | Check for Article 4 directions |
| Side extension | Half width of house | Usually needs permission in Wandsworth |
| Two-storey rear | 3m deep max | Almost always requires permission |
| Basement | N/A | Always requires planning permission |
Wandsworth Basement Policy
Wandsworth has clear basement development rules in the Basement Extensions Guidance. The policy is less restrictive than some inner London boroughs but still has important limitations.
Key Policy Rules
- No multi-level basements: Single-storey basement extensions only
- Front garden retention: At least 50% must remain, minimum 2m depth (conservation areas)
- Rear garden retention: At least half the garden depth should be retained (good practice)
- Planning required: All basement projects need planning permission, plus Building Control approval
Basement projects in Wandsworth cost £110,000-220,000 for typical 40m² excavations. See our basement extension guide for complete costs and timelines.
| Planning Type | Timeline | Typical Cost |
|---|---|---|
| Permitted development (no application) | No wait | £38k–£108k |
| Prior approval (larger rear, 3–6m) | 8 weeks | £38k–£108k |
| Householder planning application | 8 weeks | £38k–£108k |
| Conservation area full planning | 10–13 weeks | +8–12% premium |
| Basement planning application | 10–13 weeks | £112k–£152k |
Source: Mayfair Studio project data • Data as of 2026
Extension Costs in Wandsworth
| Extension Type | Cost per m² | Typical Total |
|---|---|---|
| Single-storey rear (20m²) | £1,900-2,400 | £38,000-48,000 |
| Side return (12m²) | £2,400-3,200 | £29,000-38,000 |
| Two-storey rear (40m²) | £2,100-2,700 | £84,000-108,000 |
| Loft conversion (30m²) | £1,700-2,300 | £51,000-69,000 |
| Basement (40m²) | £2,800-3,800 | £112,000-152,000 |
Conservation area premium: Add 8-12% for heritage materials and design requirements
Additional Costs
- Architect fees: £3,500-10,000 (10-12% of build cost)
- Structural engineer: £1,200-3,000
- Planning application: £206 (householder) or £462 (full planning)
- Party wall: £1,500-3,000 per neighbor
- Building Control: £700-1,800 depending on project size
Wandsworth has 76 conservation areas - London's highest count. Extension costs run £1,900–2,700/m²; conservation area projects add 8–12% for heritage materials. Standard planning takes 8 weeks; conservation area or complex applications take 10–13 weeks. Multi-level basements are not permitted, and at least 50% of front gardens must be retained.
Frequently Asked Questions
Do I need planning permission for an extension in Wandsworth?
It depends on size and location. Single-storey rear extensions up to 4m (detached) or 3m (terraced/semi) may qualify for permitted development. However, conservation areas, Article 4 directions, and listed buildings always require planning permission. Wandsworth has 76 conservation areas covering significant parts of the borough, so always check your property's designation first.
What is Wandsworth's basement policy?
Wandsworth does not permit multi-level basements. At least 50% of front gardens must remain after excavation, with a minimum 2m depth retained (required in conservation areas). For rear gardens, at least half the garden depth should be retained as good practice. All basement projects require planning permission and must comply with the Housing SPD guidance.
How much does an extension cost in Wandsworth?
Extension costs in Wandsworth: £1,900-2,400/m² for single-storey rear extensions, £2,100-2,700/m² for two-storey extensions, £2,400-3,200/m² for side returns, and £2,800-3,800/m² for basements. Conservation area projects add 8-12% for heritage materials. Total costs range from £38k for small single-storey to £180k+ for basements.
How long does planning permission take in Wandsworth?
Standard applications take 8 weeks in Wandsworth. Conservation area consultations add 1-2 weeks. Complex applications (basements, multiple storeys) can take 10-13 weeks. Pre-application advice is available for £100-400 depending on complexity and can significantly improve approval chances.