Many homeowners love their property but feel cramped, especially in Victorian and Edwardian terraced houses, where kitchens are narrow and dark. That unused alleyway running alongside your house often feels like wasted space.
You dream of a bigger kitchen, more light, or even a dining area, but moving house is costly, stressful, and often unnecessary. Most guides online only throw confusing numbers at you, leaving you unsure about the real cost of a side return extension and whether it’s worth it.
That’s where this guide comes in. Here, you’ll find a clear breakdown of how much a side return extension costs, what factors influence the price, and whether it’s the right choice for your home. From budget options to high-end finishes, this article will walk you through everything you need to know before starting your project.
What Is a Side Return Extension?
A side return extension is a popular way to make use of the narrow strip of land that runs along the side of many terraced and semi-detached houses. This space, often just used for bins or left empty, can be transformed into valuable living space.
Instead of extending far into your garden, you infill this side passage, usually connecting it to the kitchen or dining area. This design not only adds extra square footage but also improves natural light and creates an open-plan feel.
Common uses for a side return extension include:
- Enlarging a kitchen into a spacious cooking and dining hub.
- Creating an open-plan living area.
- Adding more storage, utility space, or even a small WC.
- Installing skylights or bi-fold doors for maximum daylight.
How Much Does a Side Return Extension Cost?
The cost of a side return extension varies depending on location, size, design complexity, and level of finish. On average, you can expect the following price ranges:
| Type of Side Return Extension | Low Cost | High Cost | Average |
| Small single-storey (outside London) | £30,000 | £45,000 | £37,500 |
| Small single-storey (London) | £50,000 | £95,000 | £72,500 |
| Double-storey side return | £45,000 | £120,000+ | £80,000 |
| Side return kitchen extension (fit-out) | £7,000 | £30,000+ | £15,000 |
| Side return extension per m² | £1,500 | £4,850 | £3,000 |
Key takeaways:
- In London, side return extensions are more expensive, often starting at £4,000–£4,850 per m².
- Outside London, prices are typically lower at £1,500–£2,500 per m².
- A typical 3m x 5m single-storey side return in London may cost £70,000–£120,000 once finishes, fees, and VAT are added.
Breaking Down the Costs
1. Construction (Shell Build)
This covers the walls, foundations, and roof. In London, expect £40,000–£60,000 just for the shell.
2. Fit-Out Costs
Includes flooring, glazing, heating, electrics, and plastering. Budget £25,000–£50,000 depending on quality.
3. Kitchen & Interiors
If your extension includes a new kitchen, prices range from:
- Basic kitchen: £7,000–£10,000
- Mid-range: £12,000–£20,000
- High-end bespoke: £25,000–£40,000+
4. Professional Fees & VAT
- Architect, engineer, and surveyor fees: 15–20% of construction cost.
- VAT: Currently 20% on most extensions.
5. Hidden Costs
- Party Wall Agreements: £1,000–£2,000.
- Planning fees (if not under Permitted Development): £200–£500.
- Utility adjustments (moving pipes, wiring, drainage): £2,000–£5,000.
How Much Does a Side Return Extension Cost in London?
London homeowners face higher prices due to:
- Higher labour costs.
- Expensive materials and glazing.
- Site restrictions (parking, skips, cranes).
On average:
- Basic single-storey: £70,000.
- Mid-range: £120,000–£150,000.
- High-end with glass walls and premium finishes: £180,000–£250,000.
How Much Does a Side Return Kitchen Extension Cost?
Kitchen-focused extensions are among the most popular.
- A budget kitchen side return (basic units, laminate worktops) starts around £47,000, including extension + kitchen.
- A mid-range kitchen with quartz worktops and integrated appliances may reach £75,000–£120,000.
- A luxury kitchen extension with bespoke joinery, marble, or smart appliances can cost £160,000+.
How Much Value Does a Side Return Extension Add?
Investing in a side return extension is not just about space – it’s about increasing property value.
- On average, a side return extension can add 10–20% to the value of a home.
- In London, where space is at a premium, this can mean an uplift of £100,000–£200,000+, depending on location.
- Kitchens and open-plan layouts are high on buyer wishlists, so a kitchen-focused side return can yield the strongest return on investment.
How to Choose Between a Rear and Side Return Extension?
Both options improve space but serve different needs:
- Side Return Extension
- Best for terraced or semi-detached homes.
- Uses wasted side space without taking up much garden.
- Ideal for brightening kitchens.
- Rear Extension
- Extends into the garden, offering more space.
- Works well if you have a deep plot.
- Often higher cost due to larger size.
If you want to keep most of your garden intact, a side return extension is the smarter choice. If you have a large garden and want maximum interior space, a rear extension might suit you better.
What Is the Cheapest Way to Do a Side Extension?
If you’re on a tight budget:
- Stick to a single-storey.
- Use standard materials (uPVC windows, laminate flooring).
- Choose flat roofing instead of pitched or glass.
- Avoid moving utilities like boilers or drainage if possible.
- Install a kitchen based on standard carcasses instead of bespoke.
- Phase the project – start with the shell, finish interiors later.
Budget-friendly projects can be done for £30,000–£50,000 outside London, though costs in the capital will still be higher.
Is a Side Return Extension Worth It?
Absolutely – if your home suffers from:
- A narrow, dark kitchen.
- Limited dining or family space.
- Wasted side passage.
The benefits include:
- More usable living space.
- Brighter, open-plan interiors.
- Increased property value.
Modern appeal that buyers love.
For most London homeowners, a side return extension pays for itself in lifestyle improvement and future resale value.
Most Asked Questions
1- What is a side return extension?
A side return extension fills in the narrow alleyway that runs alongside many terraced and semi-detached houses, usually extending the kitchen or living area.
2- How much does a side return extension cost in London?
Expect £70,000–£250,000 depending on size, finishes, and professional fees.
3- How much value does a side return extension add?
Typically, 10–20% of your property value, which in London can mean an uplift of £100,000+.
4- Is a side return extension worth it?
Yes – it improves daily living, increases property value, and makes homes more attractive to buyers.
Conclusion
A side return extension is one of the most effective ways to transform your home without sacrificing garden space. While costs can range from £30,000 outside London to £250,000 in London for high-end projects, the benefits in space, light, and value often outweigh the investment.
By planning carefully, comparing quotes, and setting clear priorities, you can create a stunning extension that suits your lifestyle and budget.
