If your family has outgrown your home, extending your property can be a smarter investment than moving. Understanding house extension costs in South London is an important first step in planning your project and setting a realistic budget.
Whether you’re considering a single-storey rear extension, a double-storey extension or a wraparound design, the final cost will depend on the size, specification and complexity of the build.
In this guide, we’ll explain the typical house extension costs in South London for 2026, what influences pricing and how Sunny Build helps homeowners create beautiful, practical living spaces that add long-term value.
How Much Does a House Extension Cost in South London?
Every project is unique, but the following figures provide a useful guide for homeowners planning an extension.
Extension Type
Single-Storey Extension
Double-Storey Extension
Wraparound Extension
Side Return Extension
Typical Cost (2026)
£45,000 to £80,000
£80,000 to £140,000+
£90,000 to £160,000+
£40,000 to £70,000
The exact cost of your extension will depend on factors such as the size of the build, structural work required, access to the property and the quality of finishes you choose.
The most accurate way to understand your budget is through a professional consultation and detailed quotation.
What Affects House Extension Costs?
Several factors influence house extension costs in South London.
Size of the Extension
Larger extensions require more labour, materials and time, naturally increasing the overall project cost.
Structural Requirements
Removing load-bearing walls, installing steel beams (RSJs) or making significant structural alterations will affect the final price.
Ground Conditions
Foundation depth can vary depending on the soil conditions and nearby trees, which may influence construction costs.
Kitchen and Bathroom Installations
If your extension includes a new kitchen, utility room or bathroom, plumbing, electrics and specialist installations will contribute to the overall investment.
Specification and Finishes
Flooring, glazing, lighting, roof lanterns, bi-fold doors and bespoke finishes all influence the final cost.
Planning and Design
Architectural drawings, structural engineering and planning applications should all be factored into your project budget where applicable.
Is a House Extension Worth It?
For many homeowners, extending an existing property offers better value than moving.
Benefits include:
- More living space
- Increased property value
- Improved family lifestyle
- Modern open-plan layouts
- Better use of outdoor space
- Avoiding moving costs and stamp duty
A thoughtfully designed extension can transform the way your home functions while making it more attractive to future buyers.
Do You Need Planning Permission?
Not every extension requires planning permission.
Some smaller extensions fall under Permitted Development rights, while larger projects or homes in conservation areas may require formal approval.
Regardless of planning requirements, all extensions must comply with current Building Regulations covering structural integrity, insulation, drainage, ventilation and fire safety.
An experienced building company will guide you through these requirements from the outset.
Choosing the Right Builder
When comparing quotations, it is important to look beyond price alone.
Choose a contractor that offers:
- Detailed quotations
- Transparent pricing
- Experienced project management
- Structural building expertise
- High-quality workmanship
- Clear communication
- Proven residential experience
Selecting an experienced builder helps minimise delays, unexpected costs and unnecessary stress throughout the project.
Why Choose Sunny Build?
Sunny Build has extensive experience delivering high-quality house extensions throughout South London.
We manage every aspect of your project, including:
- Initial consultation
- Design advice
- Planning support
- Structural works
- Construction
- Electrical and plumbing installations
- Internal finishes
- Final completion
Our team focuses on delivering extensions that blend seamlessly with your existing property while providing practical, modern living spaces built to the highest standards.
Areas We Cover
Sunny Build provides house extension services across South London, including:
- Wimbledon
- Wandsworth
- Lambeth
- Stratford
- Clapham
- Brixton
- Balham
- Streatham
- Putney
- Dulwich
- Tooting
- Battersea
Frequently Asked Questions
Most house extensions take between 10 and 20 weeks, depending on the size and complexity of the project.
In many cases, a professionally built extension can significantly increase both your home’s value and its appeal to future buyers.
Yes. Many homeowners remain in their property throughout construction, although this depends on the scale of the work.
A single-storey rear extension is often the most cost-effective option while still providing a substantial increase in living space.
Start Planning Your House Extension
If you’re researching house extension costs in South London, speaking to an experienced builder is the best way to understand what’s possible for your property.
Sunny Build provides expert advice, transparent quotations and fully managed building services from concept through to completion.
Contact Sunny Build today to arrange your consultation and begin planning your house extension.