Chartered Architectural Technologists | ARB Registered Architects for Basement Conversions
Transform your home with a basement conversion in London. Our architects design light-filled, functional basement spaces that add value and character. Book your free consultation today.
Transform Your Underground into Uplifting Living Space
Looking for a basement conversion in London? At Detailed Planning, we specialise in designing and delivering inspiring basement conversions that maximise your home’s potential. Whether you’re adding a family room, home cinema, or guest suite, our team of experienced architects makes the process simple, transparent, and stress-free.
Why homeowners across London choose us:
Locally grounded: We bring in-depth knowledge of London’s planning regulations to every conversion.
Transparent process: From design through to completion, your dedicated project manager ensures clarity at every stage.
Value-driven design: Expect a space that adds character and depth — without the intimidation of hidden costs or legal complexities.
Avoid Common Basement Conversion Pitfalls
Going underground doesn’t have to mean buried issues. With us, you’ll avoid:
Poor Light and Layout
We design with daylight in mind so your basement feels bright and breathable.
Planning and Regulatory Headaches
Especially if planning permission isn’t required, we’ll help you understand the process clearly.
Seamless Basement Conversions from Start to Finish
Whether you’re unlocking the potential of a new basement or enhancing an existing one, we make the process straightforward. From warm and welcoming designs to strategic planning advice, we ensure cost-efficiency and buildability from day one.
Our service covers everything:
Understand your dream — We listen, learn your goals, examine your site, and start shaping your ideal space.
Design with light and practicality — Each design balances comfort, aesthetics, and technical build integrity.
Handle planning (when needed) — Some conversions can proceed under permitted development; we clarify when and how.
Manage your build confidently — With your dedicated manager overseeing the build, expect smooth progress and expert support.
You’re not just adding rooms — you’re crafting memories.
Basement conversions often require careful consideration of planning rules — you can read the Planning Guidance for more details.
Basement Conversion Services We Offer
Whether it’s for family life, lifestyle, or investment, we help you make the most of basement conversions in London — all while enhancing your home’s value and appeal.
Why Choose Detailed Planning for Basement Conversions in London
We are London’s trusted architects in basement projects, with years of experience delivering bespoke solutions, including house renovations and more! Here’s why homeowners choose us:
Proven experience since 2011
Delivering thoughtful and buildable basement designs across London.
Designs that feel spacious and welcomin
Transforming basements into functional extensions of your home.
Home improvement projects can become overwhelming without the right guidance. Poor design, cowboy builders, and complicated regulations can lead to delays, financial loss, and anxiety. Don’t risk these pitfalls. Let Detailed Planning provide the expertise and support you need to make your dream home a reality. You deserve a home that safeguards your savings while enhancing your property’s value.
Imagine a space that improves your quality of life and makes you proud. A place where precious memories with family and friends are made.
Trusted Guidance Every Step of the Way
With over 14 years of experience, we understand how important your home is to your well-being and happiness. Our team ensures a smooth and stress-free process, managing everything from architectural drawings, planning approvals and building regulation drawings. Based in London, we provide expert advice tailored to local regulations and architectural styles, ensuring your project stays on track.
Book your free consultation today and take the first step toward your dream home!
Partner with us to design a high-value space tailored to your unique goals. Whether you’re looking to expand your home or add value to your property, we’ll help you make your vision a reality.
2. Leave the Paperwork to Us
Navigating planning permissions and regulations can be overwhelming. Let us handle the approvals, so you can be confident your project is ready for the next step—stress-free and on schedule.
3. Connect with Trusted Builders
We’ll introduce you to reputable contractors who can bring your design to life. With our ongoing support, you can relax knowing the right team is handling your project.
4. Enjoy a Space That Delivers Value
Once your project is complete, you’ll have a space that not only meets your needs but also adds financial value or enhances your home for years to come.Ready to Enhance Your Home?
In most cases, yes. However, the viability of a basement conversion depends on several factors—such as cost, access, and the practicality of carrying out the works. For some properties, the cost may not be justified by the uplift in value, so it’s important to assess this early on.
You won’t necessarily need a full survey to start with. The best first step is to speak with professionals (like our team), who can carry out a high-level feasibility review. We’ll identify the key considerations and let you know whether your property is a suitable candidate for conversion.
Because basements are built below ground, they typically involve high costs for excavation, underpinning, and specialist engineering. This type of work carries more risk to both your own property and neighbouring structures, and requires detailed planning and temporary structural designs before work begins.
If your property is listed, you will always need Listed Building Consent in addition to planning permission. If it’s in a conservation area, consent is also likely to be required.
Building regulations for basements are extensive, particularly around damp-proofing, fire safety, ventilation and means of escape. For example, “inner rooms” (rooms without direct escape routes) are not allowed, meaning you may need protected hallways or even sprinkler systems in certain cases.
The key is in the design. Lightwells and courtyards can bring natural light deep into the basement, while proper ventilation and high-quality waterproofing ensure the space remains dry, comfortable, and healthy.
Absolutely. In many cases, a basement is one of the best ways to increase the size and value of a London property. For example, adding a basement under a ground-floor flat can effectively double the usable floor area, which significantly boosts its market value.
Waterproofing is a specialist element of basement construction. We work with trusted specialist contractors who design, install, and guarantee waterproofing systems, ensuring long-term protection for your investment.
It can. Basements often require party wall agreements and carefully sequenced underpinning to protect neighbouring structures. This is a highly sensitive form of construction that requires careful planning, professional design, and compliance with legal procedures.
Typically through courtyards, lightwells, and mechanical ventilation systems. These not only bring in natural daylight but also allow for proper airflow.
Basement projects are among the most expensive forms of home extension. A typical basement beneath a London terraced house may cost from around £250,000, though the final figure depends on size, specification, and site conditions.
How long does the process take?
Design phase – around 6-8 weeks
Planning permission – usually 8–14 weeks
Technical design phase – around 8 weeks Additional time should be factored in for party wall agreements and third-party assessments, which can extend the timeline.
Design phase – discuss layouts, options, and proposals with you.
Planning applications – secure the necessary consents (often supported by specialist reports such as basement impact assessments or flood risk assessments).
Technical phase – coordinate structural engineers, waterproofing specialists, building regulations, and party wall agreements.
Construction phase – we help prepare documentation so you can tender to builders or proceed with your chosen contractor.
Basement impact assessments, flood risk assessments, and method statements Because of the risks involved, these can be significant, and should always be factored into your budget.
Not always—but you should expect considerable disruption from noise, dust, and vibration. For many homeowners, moving out during the most intensive works is the more practical option.
Yes. Courtyards and lightwells often need to be set back from pavements, trees, or neighbouring properties. The exact depth and footprint will depend on planning guidance and engineering feasibility.
It usually comes down to budget and space needs. Lofts and extensions are often more affordable and still add valuable space. However, basements can provide significantly more additional floor area, making them the best option if you need maximum space and are prepared for the higher cost.
Avoid the Stress of Poor Execution
Without the right guidance, basement projects can become overwhelming. Poor design and unqualified builders can lead to costly delays and frustration. At Detailed Planning, we offer expert support every step of the way, ensuring your project runs smoothly.
Don’t risk your investment. Choose Detailed Planning for a seamless experience.
