Cheapest Way to Extend Your Home | Loft vs Extension vs Garage Conversion

Adding more living space is one of the best ways to improve both your quality of life and the value of your home. But what is the cheapest way to do it: loft conversion, extension, or garage conversion? The answer depends on your property, your needs, and how you plan the project.

At the heart of this decision is getting the brief right. Speaking to an architect or home design professional now will help you weigh up costs, practicality, and long-term value. They can make sure you do not spend money on space that is not useful.

Extension above by Seda, architect on West London on Design for Me. See her full profile and shortlist her for your home project here.

Maximise the Space You Already Have

Before spending tens of thousands on building work, consider whether you are making the most of your existing space. An architect can often suggest clever changes such as:

• Reorganising layouts by removing unnecessary corridors or dark spaces
• Adding smarter storage solutions
• Reconfiguring under-used areas such as a dining room
• Improving flow between spaces and connection to the garden

These changes can often unlock more usable space than you expect, without the cost of a full build.

Cost Comparison: Loft vs Extension vs Garage Conversion

We recently surveyed over 100 UK architects on Design for Me to get realistic cost ranges for different home extension options.

Single Storey Extension

• Average UK cost (10m² kitchen extension): £73,495
• Outside London: £45,563
• London / South East: £90,719
• Kitchen cost alone from: £11,888 to £18,975

If you double this into a two-storey extension, costs rise to around £112,099 on average across the UK.

See our house extension cost calculator.

Loft Conversion

• Average UK cost: £74,143
• Outside London: £55,821
• London / South East: £88,000

This typically creates a simple habitable space with stairs, roof lights, and a dormer. For more ambitious projects like a mansard roof extension, costs can reach £107,425 on average across the UK.

Garage Conversion

Garage conversions are usually the cheapest option because the structure already exists. Depending on finishes and the existing services/insulation, they often fall between £6,000 and £20,000, which is a fraction of the cost of a loft conversion or extension.

Do I need planning permission to convert my garage?

Beyond Cost: What is Most Useful to You?

The best option depends on how you will use the new space:

• Loft conversion: best for an extra bedroom or home office
• Extension: ideal for larger kitchens, dining areas, or improved garden connections
• Garage conversion: good for home offices, playrooms, or utility rooms

An architect will help you prioritise what matters most to you, whether that is entertaining, quiet study space for home working, more bedrooms, or better light and connection to the garden.

The Importance of the Brief

Many homeowners feel nervous about approaching architects, worried they will be locked into expensive designs. In reality, it is a collaborative process that starts with the brief:

• The early stages are where the biggest value is unlocked
• You are not committed to the entire project by talking to an architect
• Many architects will provide initial options and a quote before you spend significant money

Finding an architect for a house viewing

Conclusion: Which Option is Cheapest?

• Garage conversion: lowest upfront cost, but limited in scope
• Loft conversion: mid-range, great for bedrooms or offices
• Extension: most expensive, but often the biggest lifestyle upgrade

The best advice is to talk to an architect early. They will help you balance cost, usability, and long-term value so the space you create works for your life, not just your floor plan.

Get Matched with an Architect, Interior Designer or Garden Designer

Ready to get started? Post your project and we’ll match you with home design professionals – all over the UK – who are a perfect fit for your brief. It’s free, fast and no obligation.

• See who’s interested in your job
• Shortlist design pros
• Arrange consultations – for free!

 

Find your home design pro

 

About the Author

Emily Barnes

Emily is the founder of Design for Me and a qualified residential architect with over 20 years of experience in home design and construction. Having worked closely with homeowners on renovations, extensions, and new builds, Emily set up Design for Me to connect people with the right home design professional for their project.

       Follow Design for Me