House Extensions in Kensington and Chelsea
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At Bigness Group, we deliver bespoke house extensions in Kensington and Chelsea, combining architectural elegance with modern performance.
From classic townhouses in South Kensington and Chelsea to mews houses in Notting Hill and luxury residences in Holland Park, our extensions enhance space, light, and comfort — built with precision and sophistication.
We manage every stage of your project — from concept and planning to engineering, interior design, and construction — ensuring a flawless experience from first sketch to final finish.
Design and Build Services
Our Kensington and Chelsea design-and-build team provides an elite full-service solution:
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Detailed survey, architectural design, and 3D visualisations
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Planning and listed building consent through RBKC Council
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Structural calculations and Building Control liaison
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Interior design, bespoke joinery, and lighting integration
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Dedicated project management with transparent milestones
With one expert team managing every detail, you get a seamless process, uncompromising quality, and an extension that adds both luxury and long-term value.
Types of Extensions We Build
We specialise in all major types of home extensions across Kensington and Chelsea, including:
• Glass Box Extensions – Contemporary architectural additions.
• Modern House Extensions – Architectural masterpieces for contemporary living.
• Single-Storey Extensions – Elegant, light-filled spaces for living and dining.
• Double-Storey Extensions – Add upper-level luxury bedrooms or studies.
• Side-Return Extensions – Perfect for period homes in Chelsea and Notting Hill.
• Rear Extensions – Transform garden-facing areas with glass and natural light.
• Wrap-Around Extensions – Seamless integration of side and rear expansion.
• Conservatories & Orangeries – Classic glazed structures with premium detailing.
• Loft & Garage Conversions with Extensions – Add new rooms vertically or repurpose existing structures.
• Basement Extensions – Create gyms, cinemas, or private lounges below ground.
Construction Standards
Every Bigness project in Kensington and Chelsea adheres to the highest construction and sustainability standards:
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Groundworks & Foundations – Engineered for precision in high-value properties.
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Structural Steelwork – Discreet RSJs and frameworks for open layouts.
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Walls & Roofs – Hand-selected materials to match listed and heritage finishes.
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Windows & Glazing – Acoustic and thermal glazing systems for urban comfort.
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Interior Craftsmanship – Custom joinery, lighting, and luxury finishes.
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Final Certification & Warranty – Building Control approval and long-term guarantee.
Local Knowledge
We have deep experience navigating Kensington and Chelsea Council’s planning and conservation regulations, including works within Holland Park, Knightsbridge, and Earl’s Court.
Our team understands the borough’s architectural heritage, ensuring every extension respects the style, scale, and quality that define this prestigious part of London.
Costs and Financing
Every extension is unique, but here’s a general guide:
| Type | Typical Cost Range (2025) |
|---|---|
| Single-Storey Extension | £45,000 – £85,000 |
| Double-Storey Extension | £75,000 – £130,000 |
| Wrap-Around Extension | £90,000 – £160,000 |
| Side-Return Extension | £40,000 – £75,000 |
💡 Factors include size, materials, access, and specification level.
We provide transparent quotes with detailed breakdowns and stage payments.
Financing options may be available through our partner lenders for eligible clients — ask our team for guidance on home improvement financing.
The Process
1. Consultation & Site Visit – We meet you on-site to discuss ideas, goals, and feasibility.
2. Design & Planning – We prepare drawings, handle permissions, and finalise the budget.
3. Construction Phase – Our project manager oversees all work, ensuring safety and communication at every step.
4. Completion & Aftercare – Once finished, we conduct final inspections and provide warranty documentation.
We also offer optional maintenance plans to keep your new space performing at its best.
Why Choose Bigness Group
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Local expertise: trusted experience in high-end residential extensions across Central London.
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Full-service approach: design, planning, engineering, interiors, and construction.
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Accredited professionals: compliant with Building Regulations and listed building standards.
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Transparency: clear costs, timelines, and dedicated project management.
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Discreet delivery: minimal disruption, maximum precision, and exceptional finishes.
With Bigness Group, your home extension becomes an architectural investment — timeless, refined, and built to perfection.
FAQ
Do I need planning permission in Kensington and Chelsea?
Yes, most extensions in this borough require planning approval or listed building consent. Our architects manage all applications and negotiations with RBKC.
How long does construction take?
Typically 12–24 weeks, depending on scope, complexity, and planning requirements.
Can you work on listed and heritage properties?
Yes — we specialise in listed and conservation properties, ensuring compliance with local preservation standards.
Do you manage interior design and fit-outs?
Absolutely. We provide complete interior and furnishing solutions for a cohesive, luxury finish.
Our Recent Projects in Kensington and Chelsea
Recent highlights include a glass rear extension in South Kensington, a double-storey family addition in Notting Hill, and a full basement conversion in Chelsea. Each project showcases the craftsmanship, discretion, and attention to detail that set Bigness Group apart in Central London’s luxury construction market.
House Extensions in London by Borough
Bigness Group designs and builds bespoke house extensions across all London boroughs, including Islington and its surrounding areas. Our expertise in planning, conservation, and architectural integration ensures every project complements both home and neighbourhood.
Barking and Dagenham / Barnet / Bexley / Brent / Bromley / Camden / Croydon / Ealing / Enfield / Greenwich / Hackney / Hammersmith and Fulham / Haringey / Harrow / Havering / Hillingdon / Hounslow / Islington / Kensington and Chelsea / Kingston upon Thames / Lambeth / Lewisham / Merton / Newham / Redbridge / Richmond upon Thames / Southwark / Sutton / Tower Hamlets / Waltham Forest / Wandsworth / Westminster
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