How Much Does a Single Storey Extension Cost in the UK?
How Much Does a Single Storey Extension Cost in the UK?
Thinking about adding a single storey extension to your home? Whether you're craving a bigger kitchen, a new dining area, or a light-filled space for family life, it’s one of the most popular and rewarding home improvements UK homeowners undertake. But let’s be honest—the big question is always the same:
How much does a single storey extension cost?
We’ll break it down for you here—jargon-free, no-nonsense, and based on real-world experience.
Average Cost of a Single Storey Extension
On average, you can expect to pay between £1,800 and £2,800 per square metre for a single storey extension in the UK.
Here’s a rough idea of what that looks like:
But cost isn't just about square footage—it depends on what you're building, where you're building it, and how complex your project is.
What Affects the Price?
1. Location
Building costs vary across the UK. Expect to pay more in London, the South East, and areas like Cambridgeshire or Edinburgh.
2. Design & Complexity
A basic square extension with a flat roof will cost less than a complex wraparound with lots of glazing, a pitched roof, or structural steel.
3. Room Type
Adding a kitchen, bathroom, or utility room? You'll need plumbing, electrics, and possibly underfloor heating—all of which increase the cost.
4. Planning & Permissions
Some extensions fall under permitted development, but many still require planning permission, building regulations approval, and maybe even a party wall agreement.
Hidden Costs to Watch Out For
Architect & Engineer Fees: Usually 8–15% of the build cost if managing the whole process
Planning Drawings & Applications: Around £1,000–£2,000
Building Control Fees: Can range from £500–£1,200
Groundworks: Costs rise if the soil is poor or drainage needs re-routing
Interior Finishes: Flooring, lighting, plaster, tiling, windows, doors, etc.
Insurance & Risk: Don’t forget home insurance and possible extra costs if anything goes wrong.
Is It Worth the Investment?
A well-designed single storey extension can significantly increase the value of your property—especially if it creates a desirable kitchen-diner, open-plan living area, or even a bedroom with en-suite.
Many homeowners see a strong return on investment (ROI), especially in competitive markets like London, Surrey, and the Midlands.
How BuildSmart UK Can Help
At BuildSmart UK, we work with homeowners just like you every day to take the stress out of extending your home. Whether you need:
Planning drawings
Building regulations & structural design
Tender management & builder recommendations
Or full Done-For-You project support
We’ve got you covered. We also offer online courses and guides for those who want to manage the process themselves but still need expert input.
Real Talk: Should You Budget More?
Yes. Always include a contingency of 10–15% in your budget for unexpected expenses—like delays, changes to design, or hidden issues with your property's structure, boiler, or electrical wiring.
FAQs
Q: Do I need planning permission for a single storey extension?
Not always. Some fall under permitted development. But it depends on your house, location, and size of the build.
Q: What's cheaper—flat roof or pitched roof?
Flat roofs are generally cheaper, but pitched roofs may last longer and add more value.
Q: Can I add a kitchen or bathroom in the extension?
Yes, but this adds cost for plumbing, drainage, ventilation, and more complex finishes.
Q: Do I need to move out during the build?
Not always. But if your only bathroom or kitchen is being replaced, you might want to temporarily relocate.
Q: How long does a single storey extension take to build?
Typically 10–16 weeks, depending on size, complexity, and weather.
Ready to Get Started?
If you're thinking about extending your home and want expert guidance from start to finish—or just need help getting planning drawings sorted—book a free call with our team today.
We’ll help you plan smart, budget confidently, and make your dream home a reality.
