How much does a house extension cost?

House extension cost guide

This guide breaks down everything you need to know about house extension costs in the UK, from average prices and cost per square metre to the different types of extensions and their price ranges. You’ll also find insights into labour and contractor costs.

In this Price Guide we will talk about:

1. House extension average cost
2. Labour costs for a new house extension
3. Different house extension styles and costs
4. How to save on your house extension project
5. Find verified house extension professionals on MyBuilder
6. FAQ: Common questions about house extension costs

House extension average cost

A house extension adds living space to your home without the stress and cost of moving. It can also significantly increase your property’s market value! Knowing the average cost of a house extension makes it much easier to plan your budget. The final price can vary depending on a few key factors, such as the size of the project, how complex the structure is and the different design features you choose.

Here’s the average cost of house extensions in the UK:

Extension type	Cost
Single-storey	£2,000 – £4,000 per m²
Two-storey	£4,000 – £8,000 per m²
Loft conversion	£1,200 – £1,500 per m²

Setting aside a contingency budget is a smart move to accommodate any unexpected expenses during your home extension project. For larger builds, consider reviewing our guide on the cost of a double storey extension.

Labour costs for a new house extension

Getting someone in to handle your house extension can make the whole process much smoother.

They’ll deal with planning rules, manage the build, and make sure everything meets proper standards.

Take a look at the fees for the different trades you may need to hire:

Service	Cost per hour
Architect fees	£50 – £150
Builder's labour	£20 – £50
Electrician	£40 – £60
Plumber	£35 – £55
Carpenter	£20 – £40
Decorator	£15 – £35

Planning a house extension and curious about the costs? To know you’re receiving the best value, it's crucial to acquire multiple quotes from verified, local professionals.

Post your job today on MyBuilder to connect with extension builders near you who can provide their local knowledge for your project.

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Different house extension styles and costs

The cost of a house extension can vary quite a bit depending on the style you choose. Each type of extension comes with its own look, layout, and price range, so it’s worth thinking about what best suits your home and lifestyle before deciding which direction to take.

Single-storey house extension cost

Single-storey extensions are a practical and cost-effective way to increase space. They are a popular choice as they are straightforward.

• Costs typically range from £1,900 to £2,400 per m²

• Influencing factors include materials, size and site conditions

Loft conversion cost

A loft conversion offers another practical and often cost-effective way to extend a home without altering its footprint. These projects are ideal for adding bedrooms or home offices.

• Costs usually range between £1,200 and £2,000 per m²

• Key cost factors include insulation, staircase installation and roof alterations

Multi-storey house extension cost

Multi-storey extensions provide extra space over two floors, making them suitable for larger households. While upfront costs are higher, cost per additional m² tends to be lower.

• Usually around 50% more than a single-storey extension

• Costs are affected by structural reinforcements and design complexity

If you're planning to build upwards, consider reading more about extension over a garage cost to explore a cost-effective way of gaining upper-level space.

Basement extension cost

Basement extensions are often the most expensive option but can be useful where above-ground space is limited. These projects involve additional excavation and waterproofing requirements.

• Costs typically range from £2,500 to £4,000 per m²

• Costs vary based on site access, waterproofing and ground conditions

If you're still feeling undecided between different build types, see our comparison on choosing between an orangery and an extension.

If you’re not sure which type of extension is right for your home or budget, it’s worth talking it through with a professional. An extension builder near you can help you explore design ideas, understand costs, and find the best approach to make your plans work in practice.

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How to save on your house extension project

You don’t have to overspend to get a great result from your extension. A bit of planning and smart decision-making can help you stay on budget while still getting the space you want.

• Set a clear budget from the start: Knowing what you can spend makes it easier to decide where to splash out and where to save.

• Get a few quotes: Prices can vary a lot, so it’s worth comparing options to see what’s included and who offers the best value.

• Keep the design simple: The simpler layouts usually cost less to build and still look great.

• Reuse what you can: Reclaimed bricks, doors, or flooring can give your new space character and save money at the same time.

• Plan ahead: Getting permissions sorted and knowing how the work will run helps avoid delays and extra costs later on.

• Pick finishes wisely: Go for affordable fixtures now, then upgrade later once you’ve settled into the new space.

Find verified house extension builders on MyBuilder

Thinking about adding an extension to your home? MyBuilder makes the whole process easier. Just post your job and you’ll hear from [local house extension builders] (https://www.mybuilder.com/extensions/extension-builder-tradespeople) who know how to bring your plans to life. You can look through their previous work, read genuine customer feedback, and pick the right fit for your budget and style. It’s a quick, hassle-free way to get your project moving.

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FAQ: Common questions about house extension costs

How long does a house extension typically take to complete?

The duration of a house extension depends on the size and complexity of the project, but most extensions take between 12 to 16 weeks to complete. Smaller, simpler extensions may take less time, while more complex projects, such as two-storey extensions or those requiring extensive groundwork, could take longer.

What permissions or approvals do I need for a house extension?

You will likely need planning permission for your extension, especially if it exceeds certain size limits or affects the external appearance of your property. Permitted development rights might allow some smaller extensions without full planning permission, but it's always advisable to check with your local council or consult with a professional to ensure compliance with regulations.

Can I live in my house during the extension project?

In many cases, you can remain in your home while the extension is being built, but this will depend on the scale of the work. If significant structural changes or plumbing and electrical work are involved, you might need to temporarily relocate. It’s essential to discuss logistics with your contractor and plan accordingly to minimise disruption.

How much value can a house extension add?

Adding an extension can significantly increase the value of your property, particularly if it enhances key living areas such as the kitchen or creates extra bedrooms. The exact boost in value depends on local property prices, build quality, and design, but it often outweighs the construction costs over time.

When is the best time of year to start an extension?

Spring and summer are popular times for extension projects due to longer daylight hours and better weather. However, starting in autumn or winter can sometimes mean more availability from builders and quicker project scheduling. The best timing often depends on your budget, flexibility, and how urgently you want the work completed.