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Red Box London

  • Fulham · Southwest London
  • Est. 2005 · Federation of Master Builders
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—— REDBOX LONDON

High Quality House Extensions In London.

Looking for a new loft, extending your kitchen, building an external building, side return or opening rooms? Red Box has the necessary expertise to undertake a house extension in London.
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Flat roof skylight above a single storey house extension

"Total professionalism and reliability."
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Painting & Decorating Association Which? Trusted Trader TrustMark Government Endorsed Houzz Best of Service Federation of Master Builders Painting & Decorating Association Which? Trusted Trader TrustMark Government Endorsed Houzz Best of Service Federation of Master Builders
—— REDBOX LONDON

How Does Our Home Extension Service Work?

For many years, Red Box has been one of the best home extension companies that Londoners have turned to for help. We undertake a wide range of extension jobs in London and beyond. We have plenty of knowledge, expertise and experience to share. Whatever plans you have for building an extension, we approach tasks in a series of clear steps.

Initial Quotation

Whatever your house extension idea, we provide a full, transparent no-obligation quote for every project. This covers ideas, needs, budget & timeframe. We price every house extension carefully. It is easy to arrange a visit from one of our team.

Project Planning

If you give us the green light we will be with you every step of the way as the project is planned. We can guide you through any extension building regulations and house extension planning permission required. Our schedule will minimise disruption during the works. You’ll always know everything is happening when it’s supposed to.

Home Survey

If we haven’t surveyed your home as part of the quotation, we will take accurate measurements. We can ensure everything fits to a tee before starting work.

Project Delivery

Our teams of builders and tradespeople are highly skilled and experienced. This means we’re confident everything will run smoothly during construction. We’ll leave your property in tip-top condition. We can finish off the painting and decorating of your house extension should you wish. All you have to do is enjoy your new space.
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About Home Extensions

Do you need more space for your home, but don’t want to move? Then a property extension may be the answer! Planning a kitchen extension, side extension, loft conversion or other structural change in your home can feel daunting. Relax, Red Box helps you at every stage from planning and design to building and even decorating.
We take the stress out of the process – allowing you to enjoy your newly improved home. We have built rear house extensions, and front, side and wraparound extensions across London. The options are endless.
We can help plan the best use of the space, suggest materials and talk you through design options. Craving extra light? We can help you with a conservatory or build in large windows, for example.
Based in Fulham, we work with clients throughout South West London and Surrey including Fulham, Chelsea, Wandsworth, Clapham, Balham, Kingston, Wimbledon and elsewhere.
Contact us for details or visit our interactive project map to see where we’ve completed home extensions.

20+

Years in business

100s

London homes renovated

FMB

Master Builder Member

5★

Houzz Best of Service

The Types Of House Extensions We Can Deliver

There are plenty of options when it comes to home extension ideas including side return extensions, wrap-around extensions and rear and side extensions. It can feel a bit confusing but don’t worry. Read on for explanations of each.

Rear Kitchen Extension

A rear building extension is a simple add on to the end of the property. It can usually give approximately another 5 metres to the home. Many opt for large roof windows to let in natural light. Rear extensions mostly have flat roofs, centre pitched roofs or monopitch roofs.

Side Return Extension

This is the most common type of extension in South West London. It involves extending the building typically by 1.25m to the side. This new section will finish flush to the back of the main part of the property. The roof will then be typically flat or pitched.

Wrap Around Kitchen Extension

A wrap around is a combination of both of the above options, it extends to the side and back providing a new kitchen or living space. Our team can talk you through the options and recommend the best approach.

Kitchen Extensions Extensions

Kitchen extensions in London are relatively cost-effective and versatile. Increasing London house prices mean moving home is often not an option. Simpler London Planning Regulations have encouraged more homeowners to extend their properties. Turning a small kitchen into a large modern space is attractive.
Our expert home renovation teams can help you find out what planning restrictions might apply in your area. We can help you work around them to get you that extra space you need. You can then trust us to get on with the job – including adding the relevant electricity and plumbing too.
Red Box has completed high-quality kitchen extensions for homeowners throughout South West London and beyond. These including rear kitchen extensions and side return extensions. Prices vary from project to project, but our team can provide a free site visit and quotation. This will help plan and provide a quotation for your specific needs.
Whether you have already started work designing & planning your kitchen or starting from the beginning, we can help. We work with a network of architects and interior designers too. They can help complete projects to the highest standard and get our clients their dream kitchen!

Single-Storey Extension in London

Planning a single-storey extension for your home? Whether it be for a kitchen, dining room, living room or playroom, it’s a great way to improve your home. More space is likely to increase your property value too. A single-storey rear extension is the most popular type. As outlined above, they are mostly used for kitchen extensions. They provide a wealth of options and can feel light and airy thanks to roof lights and popular bi-fold doors.
The cost of your single-storey extension will depend on the size and scale of your project. Prices are, however, usually calculated by square metre. Average sized single-storey extensions of 4mx5m might cost around £30,000. The real figure will depend on plumbing, power, painting and decorating. Professional fees and planning costs will need adding too. The first step is to contact us for an accurate quote. We will liaise with you throughout the entire project. All you need to do is imagine what you’ll you’re extra space for.

Double Storey Extension in London

If a single-storey extension is not enough space, why not consider something bigger. A double story extension will naturally be a bigger project. The result will, of course, lead to dramatically more space. For terraced houses, most two-storey extensions are often created at the rear of the property. They are often used to extend the kitchen and add another bedroom. Extending a semi-detached house often means a two-storey side return option. As with a single-storey extension, you need to consider your needs carefully before you start.
If the ground floor will be for the kitchen extension, do you need space for a utility room or storage? Will the second storey be used for an extra bathroom, bedroom or office? The function of each room will determine the end price. You’ll need to consider power, plumbing and so on.

—— REDBOX LONDON

Frequently Asked Questions

How Much Will A House Extension Cost?
The cost of a house extension depends on several factors, including the size of the extension, the level of specification, materials used and the complexity of the build. While average extension costs are often quoted per square metre, every project is unique and should be priced individually. Additional costs such as planning applications, structural engineering or architectural drawings may also need to be considered depending on your plans. At Red Box London, we’ll discuss your requirements in detail before providing a clear, transparent quotation with no hidden surprises, so you know exactly what to expect before work begins.
Whether planning permission is required depends on the size, location and design of your proposed extension. Many smaller extensions fall under Permitted Development Rights, while larger or more complex projects may require formal planning approval. If your property is listed or located within a conservation area, additional regulations may also apply. During your initial consultation, we’ll explain the requirements relevant to your project and help you understand the next steps before work begins.
Yes. If your project requires planning permission or building regulation approval, we can guide you through the process from the outset. We regularly work alongside architects, structural engineers and planning consultants to help ensure applications are prepared correctly. Whether you need assistance obtaining approvals or simply advice on what’s required, our team will support you throughout the planning stage, making the process as straightforward as possible.
Every extension project is different, but a typical single-storey extension usually takes around three to four months to complete once construction begins. Larger or more complex projects may take longer depending on the specification and any structural work involved. Before work starts, we’ll provide a realistic programme of works and keep you informed throughout the build. Our experienced project managers coordinate every stage to help minimise disruption while ensuring the highest standard of workmanship.
A well-designed house extension can significantly increase both the living space and overall value of your property. While many estimates suggest extensions may add between 5% and 8% to a home’s value, the actual increase depends on factors such as location, design quality, market conditions and the type of extension completed. If increasing your property’s value is one of your goals, we can discuss the most practical options and help you make informed decisions that balance investment with long-term benefits.
Absolutely. Every extension project is overseen by a dedicated Red Box London project manager who coordinates the build from start to finish. We manage schedules, organise specialist trades, monitor quality and keep you updated throughout every stage of the project. Having a single point of contact means you’ll always know who to speak to, while we take care of the day-to-day management to ensure the project runs efficiently and is completed to the highest standards.
Our projects are carried out by a combination of experienced in-house staff and carefully selected specialist contractors, including qualified plumbers, electricians and other trades where required. Regardless of who is working on site, every aspect of the project is managed by Red Box London to ensure consistent quality, clear communication and excellent workmanship. Your dedicated project manager will oversee the entire build and remain your main point of contact from beginning to completion.
Red Box London undertakes house extension projects throughout London and the South East. Availability varies depending on our current workload, so we recommend contacting us as early as possible if you’re considering an extension. We’ll discuss your project, provide an estimated start date and answer any questions you may have. Our aim is to schedule work efficiently while delivering the attention and quality every project deserves.