Beautiful, Practical House Extensions
Add space, value and comfort to your home with a carefully planned extension, designed and built by experienced UK builders.
- Rear, side return & double-storey extensions
- Planning, design & building control handled for you
- Fixed-price quotations & clear timelines
Tell us about your extension
Share a few details and our team will contact you with advice, ideas and a no-obligation quote.
House Extensions Across London & the South East
Best Builders delivers high-quality house extensions for homeowners across London and the South East of England. Whether you want a bright open-plan kitchen, an extra bedroom, a larger lounge or a full-width rear extension, our team manages every stage – from concept and planning through to the final touches.
We understand UK building regulations, local planning policies and the practical realities of building in busy urban streets. Our focus is on neat, well-managed extensions that blend seamlessly with your existing property, maximise natural light and add genuine long-term value.
Why invest in a home extension?
A well-designed extension can be one of the most cost-effective ways to improve your home in the UK:
- Create extra living space – add a home office, playroom, utility or guest suite without moving.
- Increase property value – quality extensions are highly attractive to future buyers.
- Improve energy efficiency – modern insulation, glazing and heating can cut running costs.
- Transform how you live – reconfigure cramped layouts into open, social spaces.
From modest single-storey additions to full wrap-around or double-storey extensions, we tailor each project to your property, budget and lifestyle.
Types of House Extensions We Build
Every property is different. We take time to understand what will work best for your home, street and local authority, then recommend the extension style that delivers the biggest impact.
Rear Extensions
Single-storey rear extensions are ideal for creating spacious kitchen-diners, family rooms and garden-facing living spaces. We design rear extensions that maximise daylight with skylights, roof lanterns and large glazed doors, creating a strong connection between home and garden.
Most rear extensions to houses fall under UK permitted development rights, and we can advise on when full planning permission is required.
Side Return Extensions
Many London and South East period homes have an underused side return. Extending into this area can dramatically improve a dark, narrow kitchen and unlock valuable extra floor space without eating into your garden.
Our side return extensions are designed to let in natural light, keep neighbouring properties in mind and comply with local planning policies on height and boundaries.
Wrap-Around Extensions
Wrap-around extensions combine a rear and side return extension, creating a striking L-shaped space that can transform the feel of your ground floor. This style is perfect if you want a large open-plan kitchen-living area with defined zones for cooking, dining and relaxing.
We pay close attention to the structural design, steel work and drainage so that your new space feels solid, safe and well-proportioned.
Double-Storey Extensions
Double-storey extensions add significant floor area on two levels, often combining new bedrooms upstairs with enlarged living spaces below. These projects require careful planning but can dramatically increase the functionality and value of your property.
We help you navigate planning permission, daylight/sunlight considerations and structural requirements to achieve a balanced, attractive result.
Kitchen & Dining Extensions
The kitchen is the heart of most homes. A thoughtful kitchen extension can create a light, sociable hub with an island, dining area and direct garden access. We coordinate structural works, first fix services and finishes to integrate your chosen kitchen supplier’s plans.
From underfloor heating to bi-fold doors and roof lights, we deliver a complete, ready-to-use space.
Utility Rooms, Home Offices & More
Not every extension has to be large. Compact, well-planned additions for a utility room, downstairs WC, boot room or home office can make day-to-day life much easier. We focus on storage, ventilation and practical layouts that suit modern family living.
Whatever the size, our aim is to make your extension feel like a natural part of your home.
Our End-to-End Extension Process
Extending your home is a major decision, but it doesn’t have to be stressful. We use a clear, step-by-step process so you always know what is happening and when.
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1. Free consultation & site visit
We start with a phone or video conversation to discuss your goals, budget and timescale, followed by a site visit to assess your property, access, services and structural considerations.
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2. Design, drawings & planning advice
Working with you and, where required, architectural partners, we develop layout options and detailed drawings. We advise on permitted development rights, planning permission and party wall matters relevant to your local authority.
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3. Fixed-price quotation
Once the scope is clear, we provide a detailed, itemised quotation with clear inclusions. This gives you confidence on budget before any work begins.
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4. Construction & project management
Our experienced site team manages structural work, brickwork, roofing, windows, electrics, plumbing, plastering and finishes. A dedicated project manager is your single point of contact throughout the build.
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5. Finishing, handover & aftercare
We complete snagging, arrange building control sign-off and leave your home tidy and ready to enjoy. Our aftercare team remains available for any questions.
What’s included in a typical extension project?
- Foundations, groundworks & drainage
- Brickwork, blockwork & structural steel
- Roof structure, insulation & coverings
- Windows, doors & roof lights
- First & second fix electrics and plumbing
- Plastering, flooring preparation & decorating
- Integration with existing heating systems
- Coordination with kitchen/bathroom suppliers
We tailor every schedule of works to your specific extension design and agreed specification.
Planning Permission & Building Regulations
Navigating UK planning rules and building regulations can feel daunting. Our team deals with these requirements on a daily basis and can guide you through them with confidence.
Permitted development vs planning permission
Many smaller house extensions qualify as permitted development, meaning they do not need a full planning application, as long as they meet specific criteria related to size, height, materials and distance from boundaries. We review your property and local authority guidance to confirm what is possible.
Where a full planning application is required – for example, for double-storey extensions, properties in conservation areas or flats – we assist with drawings, supporting documents and liaising with the council.
Building regulations compliance
Regardless of planning status, all extensions must comply with UK building regulations covering structure, fire safety, insulation, ventilation, electrics and more. We work closely with building control to ensure your extension is safe, legal and energy-efficient.
How Much Does a House Extension Cost?
Extension costs vary depending on size, complexity, access, specification and location. As a broad guide in London and the South East:
- Simple single-storey rear extensions may start from around £40,000+VAT.
- More complex wrap-around or high-spec kitchen extensions typically range higher.
- Double-storey extensions generally cost more per square metre due to additional structure and finishes.
We believe in transparent pricing. After your consultation and site visit, you receive a detailed fixed-price quote, so you know exactly what is included before you commit.
Arrange a Cost ConsultationRecent Extension Projects
We have completed rear, side return and double-storey extensions on terraced, semi-detached and detached properties across London and the South East.
Full-width rear kitchen extension
Light-filled open-plan kitchen-diner with roof lights and bi-fold doors in a London Victorian terrace.
Side return & internal reconfiguration
Side return infill, utility room and reworked ground floor layout to create a generous family living space.
Double-storey rear extension
Two new bedrooms and en-suite above a new kitchen-dining area, finished to a contemporary specification.
Ready to Talk About Your Extension?
Whether you are just starting to explore ideas or already have drawings, we can help you understand what is possible, how much it will cost and the best way to phase the work.
- Free, no-obligation consultation
- Local knowledge of London & South East councils
- Experienced team of extension specialists