How Much Does a Single-Storey Extension Cost in Oxfordshire?
If you’ve been dreaming about adding extra space to your home, maybe a larger kitchen, island with entertaining space, a dining area, or just a bit more breathing room for your growing family, you’ve probably wondered: “How much will it actually cost to build an extension?”
At Ireson-Bailey Bespoke Builds, we know that building costs can feel confusing if you’ve never taken on a project before. So here’s a clear, easy-to-understand guide to what goes into the price of a single-storey extension in Oxfordshire, and how to start planning your budget with confidence.
The Short Answer: A Realistic Price Range
For a single-storey extension with a mid-range kitchen and fittings, you should budget around:
£3,000 to £3,500 per square metre (m²)
That means:
A 25 m² extension might cost roughly £75,000–£87,500
A 35 m² extension might cost around £90,000–£122,500
This gives you a good ballpark figure to start planning. Once you have drawings and site details, we can refine this estimate.
What’s Included in That Figure?
This type of budget typically includes:
Foundations and structure
Brickwork or blockwork
Roof, windows and doors (dependant on range)
Basic electrics and plumbing
Plastering, flooring and decorating
A mid-range kitchen (good quality units, worktops and appliances)
Mid-range fittings such as lighting, switches and flooring finishes
It doesn’t usually include extras such as landscaping, bespoke joinery, luxury finishes, or VAT (depending on the project).
Why Costs Can Vary
Every property and project is different. Here are a few things that can affect your final price:
Ground conditions – poor soil or difficult access can make foundations more expensive. Finding a well - this has happened a number of times this year.
Design complexity – simple rectangular extensions are cheaper than those with roof lanterns or unusual shapes.
Finishes and fittings – a handmade kitchen or bi-fold doors will add cost.
Existing structure – removing load-bearing walls or relocating utilities adds work.
That’s why we always carry out a proper site visit and discuss your design ideas before giving a detailed quote.
Allow for a Contingency
Even with careful planning, small surprises can happen once work begins, perhaps an unexpected drain run or a last-minute design tweak.
We recommend setting aside an extra 10–15% as a contingency to cover these items.
Planning Your Next Steps
If you’re just starting to think about extending your home, here’s a simple order of steps:
Sketch your ideas or gather inspiration online.
Speak with a builder early, we can advise what’s realistic for your space and budget.
Get drawings and planning advice (we can recommend local designers if needed).
Obtain a detailed quote before committing.
At Ireson-Bailey Bespoke Builds, we’re happy to chat through ideas at any stage, even if you’re only exploring options right now.
A Final Word
Building an extension doesn’t have to be daunting. With the right advice and clear expectations, it can be one of the best investments you make in your home and lifestyle.
If you’d like to find out what your project might cost, get in touch with Ireson-Bailey, we’re based in Oxfordshire and have years of experience delivering high-quality extensions that fit real-world budgets. Email Hannah@ireson-bailey.co.uk