House Extensions in Merton

At Bigness Group, we design and build bespoke house extensions in Merton, helping homeowners across South West London transform their properties with light, space, and style.
From period terraces in Wimbledon and Merton Park to detached family homes in Raynes Park and Colliers Wood, we create extensions that blend architectural harmony with modern functionality.

We handle everything — from initial concept and planning to construction and interiors — delivering an end-to-end service that keeps your project simple, efficient, and stress-free.

Design and Build Services

Our Merton design-and-build team provides a complete, integrated service:

• Measured survey, design, and 3D visualisation

• Planning permission and permitted development management via Merton Council

• Structural engineering and Building Control coordination

• Kitchen, interior, and lighting design

• Dedicated project management and transparent communication

With Bigness Group, you get one expert team managing your entire project — ensuring accountability, precision, and high-quality delivery from start to finish.

Types of Extensions We Build

We construct every major form of home extension in Merton, including:

• Glass Box Extensions – Architectural designs with minimalist finishes.
• Modern House Extensions – Minimalist designs for a contemporary aesthetic.
• Single-Storey Extensions – Create open, light-filled spaces for modern living
• Double-Storey Extensions – Add valuable upstairs and downstairs space.
• Side-Return Extensions – Ideal for Victorian and Edwardian homes in Wimbledon and Colliers Wood.
• Rear Extensions – Extend into your garden for natural light and open-plan flow.
• Wrap-Around Extensions – Combine side and rear layouts for maximum space.
• Conservatories & Orangeries – Elegant glazed additions for year-round comfort.
• Loft & Garage Conversions with Extensions – Convert unused space into beautiful, functional rooms.
• Basement Extensions – Create gyms, cinemas, or private lounges below ground.

Construction Standards

Every Bigness project in Merton is built with precision and care through our six-step process:

1. Groundworks & Foundations – Designed for Merton’s soil and property type.

2. Structural Steelwork – RSJs and frames for open layouts and stability.

3. Walls & Roofing – Brick match or render with warm-roof insulation.

4. Glazing & Energy Systems – Part L–compliant materials for efficiency and comfort.

5. Interior Finishes – Plumbing, electrics, flooring, and bespoke carpentry.

6. Final Sign-Off – Building Control approval and workmanship warranty.

Local Knowledge

We have extensive experience navigating Merton Council’s planning and conservation policies, covering sensitive areas like Wimbledon Village and Merton Park.
Our designs comply with local heritage and building standards while enhancing comfort, value, and modern living.

Costs and Financing

Every extension is unique, but here’s a general guide:

💡 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.