Basement Conversion

Among the top residential architecture firms in London, Scenario Architecture has built a solid reputation expanding and enhancing homes across the city. Our architects distil the ambitions of today’s homeowners into hard-working houses that express the past and look to the future. We specialise in striking interiors that maximise space and welcome natural light. The Scenario client aspires to a new archetype for London living: open, comfortable and luxurious yet accessible.

We founded Scenario with an ambitious mandate: to adapt our signature style to the needs of a growing family. We collaborate every step of the way with our clients to create highly functional interiors that make the best use of their investment. Scenario’s bespoke architecture tells the story of the homeowner, not the architects.

Our portfolio of new and heritage properties includes Scenario House, an East London terrace house we expanded in nearly every direction to accommodate the busy and evolving lifestyle of its owners. In 2018, Scenario House was shortlisted for several prestigious prizes, including the RIBA London Awards.

Basement Conversion Your intention to convert a basement

Starting your basement conversion

We’ve drawn up this illustrated overview to help you understand each stage of your home renovation and extension. And we’ve created a step-by-step guide to help see you through the planning permission process. It deals with the ins and outs of UK planning and offers strategies for navigating the system, based on our own successes.

Most home extensions and basement conversions require planning permission from the council in question. Scenario has been successful in securing this permission on behalf of our clients.

Tip

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

Basement Conversion

Advice

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

Basement Conversion Basement Conversion with Scenario Architecture

Working with Scenario Architecture on your basement conversion

Our boutique architecture practice specialises in home expansions of every scale and complexity. We offer a truly bespoke service, collaborating with homeowners on every stage of the process, from the initial designs to the project’s completion.
All our architects are fluent with the latest 3D design and visualisation tools. They use real-time visualisations and virtual reality to choose finishes and fixtures, maximise living space and simulate natural light. Our construction information comes from accurate 3D building information modelling (BIM) technology that saves the client time and money. This case study from the Chartered Institute of Building (CIOB) demonstrates the benefits of advanced technology for domestic architecture.
Scenario is a RIBA Chartered Practice, complying with the strict health and safety measures of the Royal Institute of Chartered Architects.

Basement Conversion

Chelsea basement extension below garden level for a home gym. Chelsea, London

Basement Conversion

Extensive renovation within a conservation area of a terraced house. Camden, London

Basement Conversion

Semi basement extension and full refurbishment of a family home. Hackney, London

Basement Conversion >> Your Basement Conversion Project Further Reading

Basement conversions have got a bad rap over the years, from households digging down multiple levels and edging dangerously close to their neighbours’ property lines. These “mega-basements”, or so-called iceberg houses, cause controversy for their deluxe features, like swimming pools, cinemas, wine cellars Turkish baths and car parks.

Building below street level can significantly increase the size of a home where conservation laws restrict expanding up and out. And new rooms below the main floor almost always make financial sense in high-value areas like London. But the more commonly sought and approved versions seek to enlarge an already existing coal hole or cellar. Even the most basic below-ground extensions will cost the same as a loft conversion, yet they’ll provide far more space for the outlay – most basement conversions in London start at about 40 square metres in size, growing to nearly 200 square metres.

Most basement conversions will require local Building Regulations approval, a sign-off from the neighbours and savvy planning. As most existing subterranean spaces lack any significant head height, most require excavation and underpinning. The height of the water table and location of sewer drains are an issue. And if the space lacks any access to light, a lightwell, an opening in the home’s entryway or glazing in the interior stairwell will need to be considered. If your basement conversion forms part of a larger all-over renovation, you can fold the assessment and application costs into your overall budget.

All that aside, converting a basement makes sense for families that intend to stay put and use it. Anyone looking for extra storage space, a separate playroom for growing children or a tucked-away space for utilities will find all these can be covered off in a single excavation. A well-planned basement can be the difference between staying in a beloved city home or leaving for the outskirts.

To make the most of your investment, you’ll want to consult an architect well versed in the local building codes and permissions protocol, and experienced in converting the vernacular architecture. If your home dates back more than a century, an architect that deals in period properties will be able to assess ballpark costs and potential risks with a single meeting. A good architect will be on hand throughout your project, overseeing quality control and serving as a liaison until the basement is properly executed.

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Basement Conversion >> Scenario Architecture In our clients words

scenario-architecture-testimonial-michael

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.


scenario-architecture-testimonial-guy

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


scenario-architecture-testimonial-kauser

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.


scenario-architecture-testimonial-brendan

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-architecture-testimonial-michael-gauer

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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FAQ

Basement Conversion

FAQWho will be assigned to work on my project?
Any architectural project comprises three main aspects, Creative design, Technical design and Project Management. A successful architectural project can only be achieved when all three aspects are properly performed and harmoniously integrated by an experienced professional. But can we really except a single person to specialise and shine in all three aspects and furthermore skilfully negotiate and balance the often contradictory challenges these aspects present? The basic assumption underlying the common structure of almost all other architectural practices today is that it is possible and this is precisely what is expected from the lone and often junior Architect that would typically be assigned to run your project start to finish. Scenario works in a completely different and new way, we believe in specialism and teamwork and therefore assign three experienced specialists for each and every project. A project team in Scenario is composed of a Project Director, a Designer and a Technical Designer, seamlessly collaborating to deliver results, which are noticeably superior to anything that a single person, skilful as they may be, could ever produce.

Basement Conversion

FAQWhat is Scenario’s approach to planning?
Planning in the U.K in general and in Greater London in particular is admittedly a tricky business. It is a complex maze of policies, standards and regulations that requires specialised and up to date knowledge and skills to navigate successfully.  Over the years we developed a strong approach and an effective methodology, allowing us to maintain an outstanding track record stretching over more than a decade. Successfully securing planning permission for our clients across Greater London and the Home Counties.  The key aspects of our approach to planning are listed below: 
  • Collaborative – We start the conversation with planners early and advise most of our clients to seek pre-planning advice prior to submission of a full planning application. Our experience shows that when properly consulted and liaised with, most planning case officers will be receptive to conduct a professional dialogue, increasing chances of successes. 
  • Strategic – We tailor a custom planning strategy for each project based on its circumstances such as planning history, local context and specific challenging elements. We sometimes split applications or introduce minor tweaks to the scheme during the consideration period in conversation with the officers to prevent one contentious element from jeopardising approval of the main scheme.
  • Professional – Our experience shows that the quality and clarity of the submission in terms of background research, planning history of the property and context, precedent and of course the arguments presented to support the case has a tremendous effect on success rate. 

Basement Conversion

FAQWhat is the cost of building an extension?
Currently we recommend allowing between £2,500 and £3,000 per square metre for side extensions, rear extensions or front extensions. For basement extensions, which are most expensive way to add space to your home, we recommend that you allow between £3,000 and £3,500 per square metre. When it comes to roof extensions, our experience shows that it is better to allow a lump sum of £40,000-£60,000 for loft conversions with dormer windows and between £80,000 and £120,000 for mansard roof extensions. These ranges are based on averages from numerous actual projects that we have completed in and around London since we established Scenario in 2007. We only use these rough costs per square metre during the early stages of design to maintain awareness of your target budget until a cost professional is appointed and more accurate methods of estimation are employed. The actual cost for your project will depend on many factors, including the complexity of the design, level of structural support required, and selection of fixtures, fittings material finishes. Using these rough ranges as a guide we will work together with you in an interactive process to optimise budget and scope and find the balance that works best for you. The estimated costs per square metre mentioned above are for the build costs only and exclude VAT and professional fees.

Basement Conversion

FAQWhat is the cost of an internal refurbishment?
Currently we recommend allowing between £2,500 and £3,000 per square metre for areas which will undergo an extensive renovation. We designate an area of the project as extensive renovation if the planned works includes substantial changes to layouts, significant structural works, re-plumbing, re-wiring and full redecoration. For areas of lighter internal renovation which do not require significant changes to layout or substantial structural works but do require full redecoration, re-plumbing and rewiring, we recommend allowing between £2,000 and £2,500 as an estimated cost per square metre, we designate these areas as requiring medium renovation. If there areas in your project which only call for a light renovation such as re-plastering, and painting, installing new floor finishes and light modifications of electrics and plumbing fittings, we will designate these as areas of light renovation and recommend that you allow £1,500-£2,000 per square metre or even as low as between £1,000-£1,500 if you only have light touches in mind. The real cost for your project will depend on several different variables including the complexity of the design, extent of structural works and level of fixtures, fittings and material finishes. These estimated costs per square metre are for the build cost excluding VAT and professional fees.

Basement Conversion

FAQWhat is unique about the Scenario design process?
The scenario design process was developed, tested and perfected through over a decade of extensive delivery of residential projects within and around London, some of its key features are listed below:   
  • Scenario based design – We start each and every project with a meticulous analysis of our client’s vision, requirements and aspirations. We do this by asking our clients to imagine their everyday scenarios living in the completed house and describe their desired interaction with it. 
We then translate the resulting high definition brief into an informative and revealing 3-dimensional simulation, illuminating aspirations, requirements and patterns of habitation. 
  • Uniquely interactive - Our client’s deep involvement in the process does not stop with completion of the brief. Our design meetings are highly interactive, informal and fun. 
Sitting together in front of a real time 3D model of the proposed design with realistic materials, lighting and textures we push and pull the proposed scheme together to explore its full potential and drag and drop different materials to explore various options. hen we invite our clients to take a virtual reality tour through advanced equipment that is always available in our practice for our clients to explore their projects at different stages of development. 
  • Designed to reflect you – Based purely on your lifestyle, aspirations and requirements and free from externally imposed concepts, metaphors and pre-conceptions, a completely fresh and unique design will gradually emerge and it will tell your story not ours. 
It will not look like an image cut out of a trendy architecture magazine and not designed to intentionally impress anyone. It will feel familiar, warm and inviting and you will recognise yourself in it because it will be a genuine expression of the unique way in which you and your family wish to interact with it and enjoy it for many years to come.

Basement Conversion

FAQWhich additional consultants are required for my project?
A key aspect, absolutely necessary to ensure successful delivery of your project is appointing a suitable and competent professional team. If we work together on your project we would be appointed as your Architects and Lead Consultants and help you to assemble the rest of the professional team. Most projects in and around London will require at least four additional consultants, a Structural Engineer, a Quantity Surveyor for cost control, an Approved Inspector to ensure and certify compliance with building regulations and a Party Wall Surveyor if any work is to be done to a party wall or structure. For some projects, depending on scale, complexity and your specific aspirations it may be recommended/required to use the services of additional consultants. Including but not limited to: Planning, Heritage, Right of Light, Landscape Designer, Audio Visual and Building Services Engineer. When appropriate, we will discuss these options with you and obtain relevant quotes for all additional consultants for you to consider.

Basement Conversion

FAQHow long will it take to obtain planning permission for my project?
The standard consideration period for a residential project is eight weeks, this is the official time frame for your local council to carry out consultation with the neighbours and reach a decision.  We recommend allowing for a minimum of ten weeks from submission to decision as in practice the process always takes slightly longer for the following reasons: 
  • The decision period clock only starts ticking once the application is validated by the Council, This requires then to check that the forms are completed correctly and that the submission contains all the necessary drawings, statements and reports.
Validation can take anything from a few days to couple of weeks when the council is very busy, which is most of the time…
  • Although required by law to provide a decision within the statutory eight weeks period, it is not uncommon for councils to miss the deadline of the consideration period, normally only by a few days, sometimes longer. 
While there are some effective measures to apply pressure, which we do not hesitate to use when appropriate, it is generally beneficial for the project to bear with the council a little longer. 
  • In some cases the council may ask us as your agent for an extension of time, this may be requested due to internal reasons or as an acceptable result of a professional discussion that we are conducting with them about certain aspects of the application that they are not sure about.

Basement Conversion

FAQWhat is pre-planning and will it be be required for my project?
Once we have an initial scheme designed for your project which you are happy to proceed with, we will advise whether we recommend obtaining pre-planning advice or proceeding directly to the submission of a full planning application. Most of our projects are submitted first to pre-planning when the following applies. 
  • Our experience shows that planning officers respond better to projects when they feel consulted and collaborated with. We find that when we truly listen to their often helpful and valid feedback and treat them as consultants for the projects and not representative of an evil enforcing authority, they tend to collaborate well with us and demonstrate increased flexibility.  
  • Although the council in theory have eight weeks to consider your application, in practice they are constantly overloaded. They will only look at your application in the last few days of the consideration period. If this is the first time that they come across a scheme that they were never consulted about, our chance to secure permission for you in a single attempt is significantly compromised. 
  • The standard practice is for the council to consider the full planning application as submitted and then issue a yes or no decision. Case officers are not required or even encouraged to enter a discussion with us or accept resubmission of minor changes to the proposed scheme during the consideration period. 
In practice our established working relationships and long-standing experience working across Greater London and the Home Counties often enables us to have a meaningful discussion and even introduce minor tweaks to the submitted scheme within the consideration period and prevent the application from being rejected. The chances for this strategy to deliver the desired results increases significantly with projects which were submitted first for a pre-planning advice.

Basement Conversion

FAQWhat is Scenario’s approach to sustainability?
In the past, it was common practice for local authorities to impose sustainability standards on residential developments. However, the 2015 Deregulation Act removed the obligation on local authorities to require any standard at all, which means the only requirements having fallen back to those of the Building Regulations.  With no clear and improved targets to work towards, in collaboration with Envision (www.envisioneco.com), we have created optional Sustainability ‘Levels’ to offer our clients the chance to drastically improve the sustainability credentials of their home. These ‘Levels’ encompassing Bronze, Silver, Gold and Diamond, traverse a clear and applicable route from basic compliance with current Building Regulations all the way to the full and rigorous HQM (Home Quality Mark) certification within Level Diamond. As the packages become more elaborate in terms of sustainability, analysis and implemented measures, they provide increasing tangible benefits. Ranging from thermal and acoustic comfort and wellbeing, to reduced carbon foot print, savings on running costs and significant advantages through the planning process.  The more elaborate packages obviously entail higher cost in terms of professional fees as well as impact on the construction cost, although each sustainability ‘Level’ will endeavour to not overly burden the construction budget.

Basement Conversion

FAQWhat is building control and is it required for my project?
In a nutshell building control is the means by which Local Authorities enforce compliance with current Building Regulations.  In practice there are two main ways to go about obtaining the required advice and certification for your project, via your Local Council’s Building Control Department or via direct appointment of an Approved Inspector who is authorised to carry out the inspection and certification on behalf of any local authority.   The role of either the Council’s Building Control Officer or an Approved Inspector is to verify that your project meets all current Building Regulations. They will review and approve all the drawings, inspect the actual work carried out on site and once the project is completed, issue the final compliance certificate. Due to an open market, healthy competition between local councils and approved inspectors, the process and associated costs are almost identical. Having said that, our experience is that the private inspectors still feel and behave more as your appointed consultants and the council’s service still feels more like a statutory inspection and it is often slower and less responsive.  While it is always good to be informed and understand the process well, as your appointed architects we will take care of this aspect of the project for you and save you considering comparable quotes that we will obtain on your behalf and appointing the selected provider. You can leave this aspect of your project entirely with us.  Building control is required for almost all projects, and for all the projects we ever worked on as only minor renovation works may be exempt.

Basement Conversion

FAQWhat is the cost of building a new house?
If you are thinking about building a new house from scratch for which the term Self Build is often used, we currently recommend allowing between £2,500 and £3,500 per square metre for projects in and around London. This may sound like a very wide range initially, perhaps too wide to be useful? As soon as we can establish even a few of the basics of your requirements and aspirations for the project we can safely narrow it down and customise it to match your intentions. The key parameters that will help us to refine initial estimates are whether or not a basement is required to achieve your target floor area, the likely construction method and corresponding structural approach and of course your desired level of fixtures, fittings and material finishes. Another key parameter that we must consider right from the outset is the level of sustainability that we are aiming at, are you satisfied with the base line requirements as defined by current building regulations, or should we aim higher? Working together with sustainability experts we have created our own bespoke set of sustainability packages which allows you to place your sustainability target anywhere you wish. This can range from basic compliance to an extremely sustainable and energy efficient standard which comes with great savings on running costs, future proofing and wellbeing benefits such as improved air quality, thermal comfort, and considerate and healthier surface finishes.

Basement Conversion

FAQWhat is the fee structure used by Scenario Architecture?
The fee structure that we will offer will depend on the type and scale of your project as well as the scope required from us. The vast majority of the projects we take on are what we call ‘full projects’, these are projects for which we will provide full Architectural services from inception to completion, covering the standard scope of services offered by most RIBA Chartered Architects and more. For these full projects our fees will be calculated on the basis of an agreed percentage of the final cost of the building works exclusive of VAT and professional fees. At any given time, we will calculate our fees based on the latest construction cost estimates available until the final cost of the building works has been ascertained. Our fees will be adjusted both forward and retrospectively to reflect any increase in budget and scope of the project, and forward only (due to work already completed) to reflect any decrease in budget/scope. During early stages, our fees will be calculated based on our in-house estimation tool and once available, on estimates by the appointed Quantity Surveyor, followed by actual prices of returned tenders and finally, the contract sum reflecting any changes during construction. Under unusual circumstances we may agree to take on projects only up to a certain stage, for example up to planning, and sometimes from a certain stage if we are taking over from another Architect. For these ‘partial scope projects’ we will normally put forward a simple fixed lump sum proposal.