A Complete Guide to Budgeting Your Project
Looking to expand your living space? A house extension can be one of the most effective ways to enhance your home — adding both functionality and value without the upheaval of moving. But what should you expect to budget for such a project?
In this comprehensive guide, we explore the typical costs associated with house extensions in London, from the most popular types of extensions to key factors that influence pricing. You’ll also find practical advice on finding reputable contractors and keeping costs under control.
Why Choose a House Extension?
As property prices continue to rise, many homeowners are turning to extensions as a smart way to create additional space and improve their quality of life. Whether you need a larger kitchen, an extra bedroom, or a home office, extending your current property often works out more affordable than buying a larger home.
Of course, the cost of a house extension varies greatly depending on a range of factors, including the type of extension, size, location, and finishes. Below, we break down what you can typically expect to pay for various types of extensions in London.
Average House Extension Costs in London
Single-Storey Extension
Single-storey extensions are constructed on one level and can be positioned to the rear, side, or wrap around the property. They are ideal for expanding your kitchen, living space, or dining area.
Average cost per square metre:
£2,200 – £3,300
Rear Extension
Rear extensions extend the back of your property and often flow seamlessly into your garden space — perfect for creating larger open-plan living areas.
| Contractor Type | Low-end Estimate | High-end Estimate |
|---|---|---|
| Budget | £45,000 | £75,000 |
| Average | £54,600 | £90,000 |
| Premium | £58,500 | £97,500 |
(For a 30 sqm extension)
Side Return Extension
A side return extension makes use of the narrow alley space often found alongside Victorian and period terraced homes. This design allows you to extend sideways without compromising valuable garden space.
| Contractor Type | Low-end Estimate | High-end Estimate |
|---|---|---|
| Budget | £52,000 | £75,000 |
| Average | £63,600 | £90,000 |
| Premium | £68,250 | £97,500 |
(For a 30 sqm extension)
Wraparound Extension
A wraparound extension combines both a side return and a rear extension to form an L-shaped structure, providing substantial extra space. This option is excellent for creating expansive open-plan living or kitchen areas.
| Contractor Type | Low-end Estimate | High-end Estimate |
|---|---|---|
| Budget | £78,750 | £112,500 |
| Average | £94,500 | £135,000 |
| Premium | £102,375 | £146,250 |
(For a 45 sqm extension)
Two-Storey Extension
Adding space over two floors offers even greater versatility, whether you need extra bedrooms, bathrooms, or more living space. Though the cost per square metre is slightly higher, the overall space gained makes this a highly valuable investment.
| Contractor Type | Low-end Estimate | High-end Estimate |
|---|---|---|
| Budget | £78,750 | £112,500 |
| Average | £94,500 | £135,000 |
| Premium | £102,375 | £146,250 |
(For a 45 sqm extension)
Basement Extension
A basement extension is an excellent solution for properties where land is limited — particularly in prime areas of London. While costs are higher due to the complexities of excavation, this option allows you to expand without affecting outdoor space.
| Contractor Type | Low-end Estimate | High-end Estimate |
|---|---|---|
| Budget | £240,000 | £320,000 |
| Average | £288,000 | £384,000 |
| Premium | £312,000 | £416,000 |
(For an 80 sqm extension)
Glass Extension
A glass extension can create a stunning architectural feature, allowing light to flood into your home. Costs depend heavily on materials and design.
Average cost per square metre:
£1,350 – £3,000
Conservatories & Orangeries
If you’re seeking a more affordable way to add living space, conservatories and orangeries are attractive options.
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Conservatory: £10,250 – £16,750
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Orangery: £30,000 – £35,000
Flat Pack Extension
Flat pack extensions offer a more affordable, modular approach to building, with shorter construction times and lower costs.
Average cost per square metre:
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Budget: £750 – £1,140
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Mid-range: £1,275 – £1,800
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Premium: £1,650 – £3,600
Semi-Detached House Extension
Extending a semi-detached house typically involves similar costs to other property types, though you may need to arrange a party wall agreement if the extension affects a shared wall.
Average cost per square metre:
£1,250 – £2,500
Factors That Affect House Extension Costs
Several variables can influence the final cost of your house extension, including:
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Location: London projects are typically more expensive than those elsewhere in the UK.
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Size and complexity: Larger and more complex designs naturally cost more.
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Type of extension: Some designs, such as basements and wraparounds, are more expensive than simpler rear or side extensions.
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Quality of materials: Higher-end finishes and bespoke features will increase costs.
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Planning and administration: Fees for architects, planning applications, and party wall agreements must also be factored in.
How to Find a Reputable Contractor
Choosing the right contractor is crucial for the success of your project. Look for companies with:
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Proven experience with similar types of extensions.
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Transparent pricing and clear contracts.
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Positive customer reviews and references.
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Membership of professional bodies such as the Federation of Master Builders or TrustMark.
How to Keep Costs Under Control
To manage your budget effectively:
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Define your scope clearly at the start of the project.
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Work with an experienced architect who can help design cost-effective solutions.
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Get multiple quotes and compare them carefully.
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Avoid making major changes mid-project, which can lead to unexpected costs.
Conclusion
A well-planned house extension can add tremendous value to your home while giving you the space and flexibility you need. With careful budgeting and the right team in place, your project can be both affordable and highly rewarding.
For a bespoke quote on your house extension in London, contact our team at Eco Building Ltd today on 0207 859 4225. We are here to help bring your vision to life.
