Loft & Garage Conversions with Extensions in London

At Bigness Group, we specialise in loft and garage conversions combined with home extensions — a powerful way to maximise space, comfort, and property value without moving.
By integrating vertical and horizontal expansion, we create cohesive, functional homes that blend new floors, rooms, and layouts seamlessly with your existing structure.

From design and planning to full construction and finishing, our team delivers turn-key transformation — tailored to London’s diverse architecture and regulations.

Design and Build

Our design-and-build service ensures your conversion and extension flow together perfectly.

• Architectural design and space planning for multi-level conversions

• Structural engineering for load-bearing walls and roof adaptations

• Planning and permitted development submissions

• Staircase, lighting, and insulation design integration

• Full construction management and transparent reporting

We take a holistic approach — treating your home as one interconnected structure, not two separate projects.

Types of Loft & Garage Conversions with Extensions

We combine different configurations depending on your space and goals:

• Rear extension + loft dormer – expand the kitchen/dining area and add a master suite above.

• Wrap-around extension + loft conversion – open-plan living downstairs, office or bedroom upstairs.

• Garage conversion + side-return – create utility rooms, gyms, or studies connected to the new extension.

• Double-storey extension + loft conversion – full property transformation adding multiple new rooms.

• Integrated conversions – link all floors with new staircases and smart layouts for natural flow.

Every project is uniquely engineered to deliver balance, light, and function.

Construction

Our process ensures structural strength and perfect integration between extension and conversion:

1. Survey & Design – Measure, model, and design every floor connection point.

2. Structural Works – RSJs, floor strengthening, and roof alterations.

3. Insulation & Energy Systems – Thermal upgrades meeting current Part L standards.

4. Electrical & Plumbing – Zoned systems for both new levels.

5. Interior Finishing – Joinery, flooring, plastering, and final decoration.

6. Sign-Off & Certification – Building Control approval and warranties included.

Our team works with precision, ensuring the structure performs as one unified home.

Materials

We use high-performance materials designed for longevity and comfort:

• Structure: Steel frames, engineered timber joists, and insulated roof systems.

• Walls & Roofing: Brick match, render, or slate tiles blending with the main property.

• Windows & Glazing: Rooflights, dormer windows, and energy-efficient glass doors.

• Interiors: Custom-built stairs, storage, and modern lighting systems.

• Insulation: Acoustic and thermal materials for comfort on every floor.