Home Extensions Tailored to Your Lifestyle
Expert Design & Build Services Across London & Surrey
Expand Your Home Without the Stress
Whether you’re considering a single-storey extension, a two-storey extension, or a complete kitchen extension, Happy Building is here to help you design and deliver the perfect solution. Our experienced home extension contractors manage everything from concept to completion – including planning permission, architectural design, and construction.
Looking to add value and space with minimal hassle? We’ve completed hundreds of house extensions in London, including side returns, garden room extensions, sunrooms, and bungalow loft conversions.
What We Do
Design
Unlock your vision with the help of our expert architectural design services tailored specifically to your needs.
Our in-house RIBA accredited architects and designers will discuss, advise, design and deliver two creative concepts based on balancing excitement, practicality and cost-effectiveness.
Planning
Streamline your planning journey by trusting our expert team to take your project from design to construction.
Our remarkable record of 98% approved planning applications will put your mind at ease. Leave the necessary submissions to us, and we will provide up to two revisions to the planning proposal if required.
Construction
Experience peace of mind by letting us deliver your construction project with expertise and care.
We pride ourselves on achieving harmony between the initial design concept and the final project execution, meticulously attending to every detail until the culmination of our collaborative journey.
Why Homeowners Trust Happy Building
Local House Extension Builders – Based in Cheam, we handle projects across London and Surrey
All-In-One Team – Architects, designers & builders under one roof
- Planning & Building Control – We handle all regulations for you
- Transparent Quotes – We explain every cost clearly – no surprises
- Design-Led Approach – From orangery kitchens to glass conservatories
Types of Home Extensions We Offer
- Double Storey / Two Storey Extensions – Add bedrooms and bathrooms with minimal footprint
- Side Return Extensions – Maximise narrow spaces for kitchens or dining
- Kitchen Extensions – Add a kitchen island, larder, or extra prep space
- Conservatory Extensions – Bright, versatile spaces including glass conservatories
- Sunroom Additions – Warm, light-filled rooms perfect year-round
- Garden Rooms – Ideal for home offices, gyms or hobbies
- Bungalow Loft Conversions – Unlock unused roof space
Our Portfolio
Click through below to discover some of our recent projects, all of which we worked with the clients throughout the whole process, from design, through planning, to build.
How Much Does a Home Extension Cost?
Understanding the costs associated with a home extension in London is crucial for effective budgeting. Below is a breakdown of typical extension types and their estimated costs:
Single-Storey Extensions
In London, single-storey extensions typically cost between £2,500 and £4,000 per square metre, depending on the quality of materials and finishes . For example, a 30m² extension could range from £75,000 to £120,000. Factors influencing the cost include the complexity of the design, choice of materials, and any additional features such as skylights or bi-fold doors.
Two-Storey Extensions
Adding a second storey is generally more cost-effective per square metre. In London, the average cost ranges from £2,700 to £4,600 per square metre, depending on materials and design complexity . Therefore, a 40m² two-storey extension might cost between £108,000 and £184,000. This type of extension is ideal for adding multiple rooms, such as additional bedrooms and bathrooms.
Kitchen Extensions
Kitchen extensions are among the most popular home improvements. In London, the cost for a kitchen extension typically ranges from £40,000 to £55,000, depending on size and specifications . High-end finishes, custom cabinetry, and premium appliances can increase the overall cost.
Sunroom and Conservatory Extensions
Sunrooms and conservatories offer a cost-effective way to add living space. The average cost of adding a sunroom in the UK is around £45,000, with prices ranging from £10,000 to £80,000, depending on size and materials . Conservatories may have similar pricing, with factors such as glazing type and roofing materials affecting the total cost.
Side Return Extensions
Side return extensions are common in London, especially for terraced houses. The cost for a side return extension typically falls between £43,000 and £97,500, depending on the size and complexity of the project . This type of extension can significantly enhance kitchen and dining areas by utilising the often-underused alleyway space.
Please note: These estimates are indicative and can vary based on specific project requirements, site conditions, and material choices. For an accurate quotation tailored to your needs, please contact us.
Book Your Free Consultation Now
We’ll walk you through your options, provide honest advice, and help bring your dream home to life.
‘It’s been a pleasure working with Geo on our home extension project, which includes a rear extension, a garage conversion and a complete refurbishment of the ground floor of our semi-detached house….. The whole design experience has been very smooth and we are very happy with how our project is taking shape.’
Architectural Design for extension in Sutton – Lorenzo, Jan 2023
