House Extensions

In the era of “don’t move, improve”, Scenario finds itself among the top residential architecture studios in London for high-end extension projects. Our portfolio of distinctive, highly functional single-storey extensions project, side-return extensions, rear extensions project, basement extensions and loft extensions give period properties new purpose and help transform London’s architectural landscape.

We established Scenario in 2007 with a vision to maximise living spaces to their greatest potential. Our boutique practice takes a considered, collaborative approach to our clients’ habits, hobbies and aspirations, delivering contemporary home extensions that tell a story about the owners – not the architects.

Our landmark project Scenario House, an East London Victorian home with a unique, light-filled side-return extension, was covered widely by the media and shortlisted for several prestigious architecture prizes – including the 2018 RIBA London Awards. It demonstrates our innovative and tailored approach to building home extensions onto period properties for 21st century lifestyles.

House Extensions Your project

Tackling London extensions

If you plan to take on a house extension in London, we’re happy to help, whether you’re planning a single-storey extension, side-return extension, basement extension or rear house extension.

We’ve created a brief illustrated overview to help you understand each stage of the house-extension process.

Most house extension projects in London require planning permission from the local council. With our successful record securing planning permission on behalf of our clients, we can claim home advantage across London.


Discover if your chosen architect has had success pushing planning applications through your local council. Visit the “planning applications” section of your council’s website and enter the architect’s name in the search criteria.

House Extensions


To help you understand what it takes to obtain planning permission in London for a house extension, we’ve created this helpful guide. Download it below.
Planning guide

House Extensions Your house extension project >> Scenario Architecture

Working with Scenario Architecture on your house extension project

Scenario is a boutique architecture studio focused on improving homes with spacious, contemporary extension projects across London and beyond. Through our bespoke architecture service, we tackle projects of every scale and complexity, from modest single-storey extensions to side-return extensions project, basement extensions, loft extensions and rear house extensions project.

Our highly skilled architects can take you step-by-step through the challenge of building a house extension. We’ll collaborate closely with you from the initial drawings, detail design and planning, guiding you through the tender and construction process and completing your house extension on time and on budget.

Early adopters of the latest drafting and building technologies, we use innovative 3D design and visualisation tools as a standard for all our house extensions. Our experience has shown that real-time visualisations and virtual reality are extremely efficient tools for choosing finishes, fixtures and fittings, and simulating natural light.

We use 3D building information modelling (BIM) to produce reliable construction information, so all our project data comes from an accurate 3D model. Using this technology collaboratively with consultants and contractors is proven to save our clients time and money. This Chartered Institute of Building case study featuring a Scenario project demonstrates the benefits of this advanced technology for house-extension projects.

Scenario Architecture is a RIBA Chartered Practice. We comply with all the criteria of the Royal Institute of Chartered Architects, covering insurance, health and safety and quality-management systems.

House Extensions

Fireplace detail in a Victorian house extension. Hackney, London

House Extensions

Basement extension in a Conservation Area. Hampstead, London

House Extensions

Conservation Area House Extension, London

House Extensions Your project >> Further Reading

There are few world-class cities where you can own your own house and convert it for your needs, and none as exciting as London. The city’s rich stock of residential housing has great potential for improvement. If you already own property in the capital and can’t justify the costs of moving house, renovating and extending your existing property may be the right move for you. Best of all, you’ll be able to stay in the neighbourhood you know and love.

Strict planning regulations in neighbourhoods rich with heritage housing make house extensions a challenge for some. Seeking the help of an architect, rather than going directly to a standard-issue builder or home-extension specialist, means the specific character of your home will be respected and enhanced. An architect will unlock potential and use materials in an original way that can complement your home’s historic appeal.

Once you’ve found an architect whose style and personality balance your own, the process of transforming your home will fall into place. Together you can collaborate on tailoring the original bones to your personal lifestyle with detailed specifications, starting from the party walls inward. Even if planning regulations are stringent in your neighbourhood, you’ll usually be able to extend outwards at least enough for an extra room or two – taken from wasted outdoor space, eaves in a pitched roof or awkward corners you didn’t even know you had.

You could extend a kitchen to incorporate an eat-in breakfast room, add an en suite bathroom, a bedroom for a new child or a home office. In a neighbourhood with newer housing stock, like a London suburb or brownfield development, more involved home extensions may be possible, like wraparounds incorporating a side return and rear, a second storey, garage topper or double-height rear extension.

House extensions are carried out in a more compassionate way today than they’ve ever been, and a good architect will strive to preserve original architectural elements – like decorative cornicing, ceiling roses, skirting boards, dada rails and picture rails – while giving your home the modern openness so many desire. Pivoting doors and Crittall-style steel windows are brilliant complements to period decorations and antique brick.

Once you’ve committed to the process, a house extension will make additional changes easier and less cumbersome, like new sash windows, flooring or a fresh paint job. They could be done concurrently with the structural work, pull everything together and help you get a good-as-new home that works with your unique way of life.

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House Extensions Extension Cost

The House Extension Cost varies. This will depend on the scale, design, exterior materials and interior finishes of your extension. Before designing an initial concept for our clients, we discuss their big-picture aspirations and daily requirements.

When we budget the House Extension Cost on any home, we must consider the different types of extensions projects. Extending upward with a loft extension, for example, is often significantly cheaper than a side-return extension and rear house extension and most definitely a basement extension.

We understand our clients’ desire to understand the cost of building an extension before committing to the process. For a single-storey extension – be it a side-return extension or rear house extension – we allow between £2,500 and £3,000 per square metre, depending on finishes. These figures can also apply to renovating the existing areas within a house.

Excavating a new basement is a great way to add significant floor space to your house with limited planning regulations. However the House Extension Cost per square metre is, by far, the highest in a basement. We allow between £3,000 and £3,500 per square metre, subject to finishes.

House Extensions Extension Cost >> Further Reading

You’ve bought a home. In and around London, that’s no mean feat. Nearly any property you purchase in the southeast will retain or accrue value. When and if it turns out you need more living space, you’ll want any enhancements you make to the size of your home to enhance your asset, too.

A good architect will factor in your home’s location, layout, structural integrity and the size of your family to make your project work for you and your budget. A house extension cost shouldn’t cancel out the benefits of a house extension.

Unless your investment is a purpose-built flat, you should be able to gain extra space that suits your lifestyle. If you own just part of a house, you can built up, down or out, depending on your specific location. If you own the entire house, chances are better you can add substantial square footage.

In some neighbourhoods around London, loft extensions and side-return extensions (recouping the side-rear void often left open between terraced houses) are grouped under “permitted development”, which means they don’t require planning permission from the local council if the final plans heed the extended volume requirements of the area. Avoiding time-consuming planning applications will save you money in the short run.

On the topic of money: it’s always difficult to project a house extension cost without evaluating the home in question, the resident family and their plans. But it’s likely you can nearly double the size of your home’s original square-metre floor area at a fraction of the cost of the original house, even at upwards of £2,000 per square metre. Plus you will, of course, gain a nearly new living space without paying the stamp duty and agents’ fees associated with moving house – although you may need to purchase renovations insurance.

As with most building-related activity, it is wise to source three to five quotes for a house extension. With a range of budgets to hand, you’ll be able to assess which seem low, high and just about right, and choose accordingly. The foundation, walls and roof will soak up about 15% of your costs, followed by Velux and rear glazing.

You’ll want to price fixtures, fittings, appliances and any upgraded materials separately, so as not to be shocked when you receive that last bill – new kitchens are particularly dear, so keep your eyes out for deals and floor sales in the months leading up to a project. Once you’ve agreed on a budget, set up a payment plan with your architect and builders that works for everyone.

House Extensions >> Scenario Architecture In our clients words


Great ideas and vision to help with our substantial improvement of a Victorian terrace. In our experience Scenario’s method prioritises the final result. That may mean more professional fees or higher quotes from contractors, as they understand the exact requirements.


Great, professional service. Good drawings and models and ultimately passed planning at the first attempt with Hackney Council. Would certainly recommend!


Scenario Architecture have created an outstanding design and space that was beyond my expectations. The design was through their unique process of understanding the client’s daily scenarios and collaborating with the client to come up with a unique design. The design process is one of the most memorable parts of the process and they also stretched my existing ideas to help create this unique space. A stress free journey throughout the whole process which Scenario were indispensable by giving advice on many difficult design and build decisions.


We wanted to renovate our house in a conservation area in central London. Given this involved a complete demolition and new build with an extra floor on top, getting planning approval was always going to be tricky. Scenario did an amazing job on the new house ‘envelope’ and throughout the planning phase. We couldn’t have wished for better from them and having succeeded in gaining planning approval owe them a very big ‘thank you’.


Scenario were great at thinking imaginatively and coming up with a design for a ground floor extension that was more ambitous than other architects we spoke to. They also helped us find a contractor who was able to complete the project working within timescale and our tight budget. I would recommend for mid to large sized projects with sufficient budget to allow for full utilisation of their creativity.

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