House Extensions in Hillingdon
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At Bigness Group, we design and build high-quality house extensions in Hillingdon, helping homeowners across West London unlock new space and elevate their homes.
From family houses in Uxbridge and Hayes to period properties in Ruislip and Northwood, we deliver extensions that combine design excellence, durability, and energy efficiency.
We manage every step — from planning and design to construction and finishing — ensuring your project is handled professionally, transparently, and on schedule.
Design and Build Services
Our Hillingdon design-and-build team provides a complete start-to-finish service:
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Measured surveys and architectural drawings
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Planning and permitted development guidance through Hillingdon Council
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Structural design and Building Control compliance
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Interior layout, kitchen, and lighting integration
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Dedicated project management with clear communication throughout
With Bigness, one expert team handles everything — guaranteeing accountability, consistency, and exceptional results.
Types of Extensions We Build
We construct all major types of house extensions across Hillingdon, including:
• Glass Box Extensions – Contemporary architectural additions.
• Modern House Extensions – Sleek designs that fuse architecture and innovation.
• Single-Storey Extensions – Expand your kitchen, dining, or family area with natural light.
• Double-Storey Extensions – Add bedrooms or offices above while extending living space below.
• Side-Return Extensions – Perfect for semi-detached and terraced homes.
• Rear Extensions – Create spacious, modern garden-facing living areas.
• Wrap-Around Extensions – Combine side and rear builds for full open-plan layouts.
• Conservatories & Orangeries – Glazed extensions for all-season comfort.
• Loft & Garage Conversions with Extensions – Add new rooms vertically or repurpose existing structures.
Construction Standards
Every Bigness project in Hillingdon follows our proven six-step construction process:
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Groundworks & Foundations – Designed for local soil and property type.
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Structural Framework – RSJs and beams installed for strong, open layouts.
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Walls & Roofs – Brick match or rendered finishes with full insulation.
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Glazing & Energy Systems – Energy-efficient materials meeting current regulations.
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Interiors & Finishes – Plumbing, electrics, plastering, and joinery.
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Final Approval & Warranty – Building Control certification and long-term guarantee.
Local Knowledge
We’re experienced with Hillingdon Council’s planning policies and Building Control regulations, including work in conservation areas such as Northwood Hills and Uxbridge Town.
Our understanding of local standards ensures every extension gains approval quickly and complements its surroundings.
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: in-depth understanding of Hillingdon’s housing stock and regulations.
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Comprehensive delivery: design, planning, and build under one contract.
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Certified professionals: compliant with all UK Building Regulations.
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Transparent pricing: itemised quotes and milestone payments.
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Proven record: trusted by homeowners throughout West London.
Bigness Group delivers extensions that enhance homes, lifestyles, and long-term property value.
FAQ
Do I need planning permission for an extension in Hillingdon?
Smaller projects may fall under permitted development, but large or multi-level builds require planning. We handle all submissions and approvals.
How long will the build take?
Most single-storey extensions take 8–14 weeks, while larger or double-storey projects take 12–20 weeks.
Do you match materials to existing homes?
Yes — we carefully source bricks, tiles, and finishes for seamless integration.
Do you provide kitchen or interior design services?
Absolutely. We manage full fit-outs, lighting, and joinery within your extension build.
Our Recent Projects in Hillingdon
Recent builds include a wrap-around family extension in Hayes, a double-storey addition in Ruislip, and a modern kitchen-living extension in Uxbridge.
Each project reflects our commitment to design precision, structural quality, and on-time delivery — built for real life, not just showrooms.
House Extensions in London by Borough
Bigness Group delivers expertly designed and built house extensions across all London boroughs, including Hillingdon and West London’s surrounding areas. Our knowledge of local planning rules ensures efficient approvals, beautiful designs, and flawless construction every time.
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
Practical thinking for better-managed buildings.
Guidance, technical insight and practical perspectives on compliance, maintenance, building performance and long-term improvement.
