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Single-storey extensions are one of the most common forms of home improvement in London. They are often used to open up kitchen, dining and living spaces to the rear of a property, but their potential is not limited to this. A single-storey side extension, for example, could provide an additional bedroom, home office, utility room or other practical space, depending on your needs and brief.
A single-storey extension is, quite simply, an extension built at one level. As an addition to the existing house, it will typically extend from the rear, side, or both, and on rare occasions from the front.
While single-storey extensions are often relatively simple in form, they can be a highly effective way to add valuable space to a home. They can also provide an opportunity to introduce something more expressive and creative, particularly at the rear of a property where the impact on the streetscape is often limited.
At Armstrong Simmonds we have designed lots of single storey extensions. Depending on the context, they can take a number of forms. Some typical arrangements might be as follows:
Armstrong Simmonds Architects will work with you to develop a concept design, sketching layout options to explore the potential of the property. We will also carry out a full measured survey of the property and its surroundings, allowing us to produce an accurate set of drawings.
Following on from the briefing we will prepare a set of scale drawings reflecting the range of ideas discussed. We will prepare and submit the planning application, liaising with the council as needed throughout the process. Our extensive experience will help facilitate a smooth planning process.
To help you visualise the space in three dimensions we can produce internal and / or external views of your project. This can also be a useful tool to demonstrate the merits of the scheme to planners.
We will produce detailed technical drawings including drainage and electrical layouts, consulting with you to ensure the design meets your needs. We will then submit to building control and manage the approval process. As part of our architectural services during this process we can assist you in appointing other consultants, for example the structural engineer or party wall surveyor.
We offer interior architecture and design for a high spec finish. We can produce further detailed information integrating specialist glazing components, floor finishes, joinery and bespoke staircase design as required.
We provide Interior design architecture services ourselves or through collaboration with other London based Interior Designers, who may also be appointed by the client.
We are happy to specify FF&E (furniture, fittings and equipment) for the project, providing a complete “one-stop” shop for your development.
We will help you make an informed choice on an appropriate contractor. We maintain a selective tender list of contractors especially in the local London area, who we have experience working with on site. We will prepare tender documentation and appraise their quotes.
Armstrong Simmonds Architects facilitates the implementation of the design by administrating a contract between you and the contractor. Amongst a wide array of architectural services, this will include undertaking site visits to monitor the quality of construction and handle any on-site queries from the contractor.
There are a few different roof forms to choose from, and they do materially affect how the space feels. However, site and planning constraints and the existing context play a big part in what is possible.
It’s important to note that these are broad, general terms and are not necessarily mutually exclusive. In practice, single-storey extension designs often combine different approaches depending on the existing property, the surrounding context, planning constraints and the desired architectural character.
For example, a wrap-around extension might incorporate both pitched and flat roof elements; a roof might use a dual-pitched form; or a flat roof could incorporate a fully glazed section. There are many possible combinations and variations, and the best approach will depend on the particular property and the design you are trying to achieve.
Single-storey extensions often require planning permission. However, some proposals may fall within the scope of permitted development, meaning that a full planning application may not be necessary. Even where it appears a proposal qualifies as permitted development, we would generally recommend applying for a Lawful Development Certificate (LDC) to formally confirm this. This provides certainty that the proposal meets the permitted development rules and removes any doubt over whether planning permission is required.
Permitted development legislation can contain some surprisingly tricky nuances, so having the Council formally review the proposal is worthwhile. It is also important to remember that permitted development rights are not the same as an automatic right to build anything you like – there are specific limitations and conditions that need to be met.
Whether applying for planning permission or a Lawful Development Certificate, the Council will typically aim to determine the application within around 8 weeks. This can vary depending on the Council’s workload, the complexity of the proposal and how quickly the application is validated.
Building Regulations are separate from planning permission. They set the technical standards that a building project must meet to ensure it is safe, healthy, energy efficient and properly constructed. They cover a wide range of elements, including structure, fire safety, drainage, insulation and thermal performance, ventilation, damp and waterproofing, and much more.
If you fancy some light reading, the Government’s Approved Documents set out the guidance on how these requirements can be met! Building Regulations compliance is typically developed and checked as part of the technical design process, rather than at the planning stage.
What a single storey extension costs in London depends on its size, the structural work required, the specification and the conditions on site. Two extensions of identical floor area can land a long way apart. The variables that tend to matter are:
Where similar projects can vary dramatically in cost is often in the glazing, joinery, finishes and kitchen specification. The underlying building shell and structural works might cost broadly the same, but what you choose to fit out and finish the space with can make a significant difference to the overall budget.
For example, a kitchen could cost £10,000 or £100,000 depending on the design, materials, appliances and level of specification you choose. The same principle applies to glazing, flooring, sanitaryware, bespoke joinery and finishes, which is why two extensions of a similar size and design can ultimately have very different overall costs.
Professional and statutory costs sit on top of the build figure rather than inside it, and they cover design, structural engineering, building control, planning fees and any specialist reports the project might need.
We are glad we found Armstrong Simmonds Architects to help us on our first project. We had bought a run-down terraced house near Clapham Common with the goal of extending and refurbing to increase value. John initially impressed us by first listening carefully to what we wanted to do, then showing us creative ways to achieve the results and finish we were looking for.
Safe to say we certainly have managed that and both John and Alan have been instrumental in doing so. The guidance and consideration at every step have exceeded our expectations and Alan’s attention to detail during the build has been critical for the high standards we have set for this project.
They have provided us with a service which reflects every stage of the design and build. Starting with the initial drawings, schedule of works, tendering and interior design. We also employed ASA for Contract Administration to be the key middle-man between us and the builder, which they were happy to help.
We are now underway with our second project with ASA and they have been able to deliver the final drawings for planning within a fairly tight time frame, without hindering on quality. I know the whole team worked hard to help bring our vision to life and it’s been brilliant working with them over the last 18 months. They have shown a great ability to solve any issues that arose quickly and are able to communicate effectively with different contractors at all levels. I have no doubt the next redevelopment project will go well.
We chose Alan and John for our extensive project and incredibly pleased with that choice and the result. We have a Victorian terraced house and wanted to do a classic loft conversion and ground floor extension. The Armstrong Simmonds team provided a vision which achieved our goals, but with a design we could have never have thought of ourselves which we love. We used them from start to finish and are incredibly glad we did. Alan supported us through the tender and renovation processes, and we are incredibly pleased with the end-product and the quality of work of builder Cezar of Vecchini. We would highly recommend Armstrong Simmonds for their vision, design thoughtfulness and exceptional assistance through the project. Thanks team!
We worked with Alan and the team from Armstrong Simmonds for 3 years from start to finish to achieve the full renovation of a London townhouse. It was a challenging brief given the nature of the property but collectively what has been achieved is an outstanding end result. Alan and John thoughtfully incorporated our vision with the realities of converting an old Victorian house and the scrupulous attention to detail, symmetry and balance achieved in the design were instrumental in us choosing Armstrong Simmonds in the first place.
In addition Alan supported us through the tender and during the renovation working with our excellent builder Cezar of Vecchini to deliver the brief. I would highly recommend if you are looking for a team to turning your vision to the end product with a very high attention to detail while still being good humoured and a generally great guy to work with. Thanks again team. Dom and Kamilla
John and his team have been brilliant to work with for our full house renovation and extension in SW London. Our house is quite unique and that combined with it being in a conservation area we knew it wouldn’t be a straight forward planning process – but Armstrong Simmonds did a fantastic job and helped us navigate us through every step. We couldn’t be happier with the detailed design and outcome.
If you are planning a single storey extension in London, we would be pleased to hear about it. Armstrong Simmonds Architects takes the project from feasibility through planning and technical design to completion on site. You may also want to read about terraced house extensions or our wider house extension service.
Call 020 7228 1324 or email [email protected].
Architect's studio/ Single Storey Extensions
