CSMANLTD is a trusted name among basement contractors in London, offering expertly planned and executed basement construction services. Whether you are a homeowner expanding your living space or a developer preparing a new site, we deliver strong, safe, and cost-effective results.
Our experienced team includes engineers, designers, surveyors, and builders who work closely with clients throughout the entire project. We help you plan efficiently, build smartly, and maximize value at every step.
As one of the most experienced basement builders in London, we assess the unique challenges of each site and deliver practical, tailored solutions. From under-house basements to garden-level extensions, we ensure every build meets structural, planning, and safety requirements.
We regularly work with developers from the early stages of planning. Our team prepares the site while architectural designs are finalized, which speeds up the overall construction process and helps reduce project costs.
We also offer flexible working models, including labour and plant-only services, depending on your requirements.
Already have a basement that feels underutilized or outdated? Our London basement renovations team helps you transform it into a modern, functional space. Whether it’s a gym, home office, guest suite, or media room, we design and deliver spaces that are practical, compliant, and ready to use.
We help you save time, reduce costs, and build better.
Basement Construction
We provide complete basement construction services including under-house and garden basements. Our team manages excavation, waterproofing, and structural stability for long-term safety and performance.
Basement Conversion, Extension and Excavation
If you already have a basement, we can convert or expand it. From cellar conversions to full basement extensions, our team ensures structural safety and compliance with all building regulations.
Underpinning
We provide underpinning to strengthen existing foundations before or during basement construction. Each solution is designed based on your property’s soil and structural profile.
Precision underpinning ensures your building remains stable and safe.
Demolition
We carry out controlled demolition of buildings or sections before construction begins. Our team handles all permits and safely manages disposal for both partial and complete clearances.
Groundworks
CSMANLTD provides full groundwork services including drainage, ducting, site clearance, and access roads. We prepare the site with safety, efficiency, and full regulatory compliance.
Piling Contractors London
As experienced piling contractors in London, we offer methods such as mini piling, CFA piling, and rotary bored piling. These solutions are ideal for challenging ground conditions and tight access spaces.
Piling ensures strong, deep foundations for all building types.
Super Structure
We build reinforced concrete frames and structural steelwork. Our super structure services support safe vertical expansion while ensuring load-bearing and fire resistance standards are met.
CSMANLTD serves all London boroughs. Whether your site is in North, South, East or West London, we are your dependable London basement contractors for high-quality construction and renovation services.
Looking for reliable basement contractors in London? Contact CSMANLTD for a free consultation. We are ready to help you plan, design, and build your next basement project with confidence.
The cost of building a basement in London depends on several factors, including the size, depth, site access, soil conditions, and design requirements. On average, it can range from £2500 to £4000 per square metre. Contact CSMANLTD for a tailored quote based on your property.
In many cases, basement construction or excavation under your home in London will require planning permission, especially if it involves structural changes, external alterations, or changes to drainage. Our team can help you assess what permissions you need and guide you through the application process.
Most basement construction projects take between 12 to 24 weeks, depending on complexity, access, and whether the space is being excavated or simply renovated. CSMANLTD provides clear timelines during the planning phase to help you stay informed and on schedule.
Yes. We specialise in basement conversions, including turning existing cellars into fully functional living areas. Whether you need extra storage, a home office, gym, or additional bedroom, we ensure structural safety, waterproofing, and high-quality finishes.
CSMANLTD offers experience, transparency, and a practical approach to every project. We are trusted basement builders in London with a proven track record of delivering safe, affordable, and high-quality basement construction and renovation services.
TESTIMONIALS
We hired CSMANLTD to design and build a basement under our family home, and the entire process was seamless. Their team took care of everything—from underpinning and excavation to drainage and structural integrity—offering expert advice at every stage. The project was completed on time and within budget. We now have a stunning living space that has transformed our home. Highly recommend their design and build service!
construction worker
CSMANLTD has become our go-to partner for pre-construction groundwork and basement development. Their in-house engineering team provides invaluable insight during the early stages, allowing us to begin on-site work while final designs are being approved. Their ability to handle piling, deep excavations, and below-ground utilities has saved us significant time and cost across multiple projects. A truly unique and reliable approach to construction.
construction worker
We collaborated with CSMANLTD on a mixed-use development requiring complex temporary works and deep foundation solutions. Their expertise in structural engineering and piling was evident from day one. They delivered a robust, cost-effective design-build solution that kept the project on track. Safety was a top priority on site, and their team operated with professionalism throughout. A standout contractor in the industry.
construction worker
As architects, we value contractors who understand both design intent and structural feasibility. CSMANLTD bridges that gap perfectly. Their in-house engineers work closely with our team to optimise structural frames, foundations, and basement construction—often suggesting innovative, cost-saving alternatives without compromising safety. They are a true extension of our professional team.
construction worker
Our Victorian house had foundation issues and limited space. CSMANLTD assessed the structure, recommended underpinning, and constructed a full basement beneath our garden—maximising space without affecting the main house. The work was clean, safe, and incredibly well-managed. Now we have a gym, cinema room, and extra bedroom. We couldn’t be happier with the result.
construction worker
