How Much Will a Double Storey Extension Cost?

Thinking about adding a double storey extension to your home? We don’t blame you!

Whether you need extra bedrooms for a growing family, want to create more living space or simply increase the long-term value of your property, a two-storey extension can completely transform the way you live.

But before building work begins, there’s one major question to ask: how much does a double storey extension cost?

The truth is, there’s no one-size-fits-all answer. The cost of a two-storey extension can vary significantly depending on the size of the build, the specification you choose and where you live in the UK.

That’s why we here at West Midlands Building Company have created this guide – helping you understand the average costs involved, what factors affect pricing and answering some of your most common questions! Let’s get started.

Average Cost Of A Double Storey Extension In 2026

In 2026, the average double extension cost in the UK typically ranges between £2,000 and £4,000 per m², depending on the complexity of the build and the quality of finishes chosen.

Here’s a rough guide based on average UK pricing for two-storey extensions in 2026, broken down by size and square metre:

• Small double storey extension (30–40m²): £60,000 – £110,000
• Medium double storey extension (40–60m²): £90,000 – £160,000
• Large double storey extension (60m²+): £150,000 – £250,000+

It should be noted that these costs are just averages, and many factors can affect pricing. Every property is different, and so is every project. Speaking directly with an experienced builder (like us here at WMBC) will always give you a far more accurate understanding of costs.

The final answer to how much a double storey extension costs depends on several important factors, from the design itself to the finish you’re aiming for.

Factors that can Affect the Cost of a Double Storey Extension

Size of Extension

One of the biggest influences on price is the overall size and layout of your extension.

Double-storey extensions are often more cost-effective per square metre than single-storey builds because the foundations and roof structure are shared across two levels. 

However, naturally, the larger the build, the greater the overall investment!

• Small Double Storey Extension (30–40m²)

A smaller two-storey extension is ideal for homeowners looking to add a bedroom upstairs while extending a kitchen or living space downstairs.

This type of extension can make a huge difference to day-to-day living without dramatically reducing outdoor space. Plus, smaller projects usually have lower overall costs.

Top tip: Sometimes the price per square metre can be slightly higher due to fixed costs such as design, structural calculations, and groundwork, so working with an expert (like WMBC) can help you save money during your renovation. 

• Medium Double Storey Extension (40–60m²)

For many households, this is the perfect balance between added space and affordability.

Medium-sized extensions can comfortably accommodate larger kitchens, additional bathrooms, home offices or multiple bedrooms. They also tend to offer the best return on investment in terms of property value and lifestyle improvements.

• Large Double Storey Extension (60m²+)

If you’re looking to completely revitalise your home or create a substantial amount of additional living space, a larger extension may be the right choice for you!

These projects often include open-plan living areas, luxury master suites, large glazing systems and premium architectural features. Of course, however, this does come with the largest price tag.

Type Of Extension

The style and positioning of your extension also affect the overall budget.

For example, side extension two-storey projects costs can differ from rear extensions because of access limitations, structural requirements and the impact on neighbouring properties.

Likewise, the cost of double storey side extension builds often depends on whether internal walls need to be removed, drainage needs relocating or foundations are more complex than expected.

Wraparound and L-shaped extensions also tend to involve higher construction costs due to increased structural work.

Quality Of Finish

The materials and finishes you choose will also have a big impact on the final cost of your extension! Here are some of the options:

• Basic / Budget Finish

If you’re working to a tighter budget, choosing standard materials and simpler finishes can help control costs while still delivering a high-quality result.

This might include standard flooring, off-the-shelf fixtures and more straightforward structural designs.

• Mid-Range Specification

The ‘sweet spot’, this is where many people tend to land.

A mid-range finish balances quality, durability and aesthetics – typically including good insulation, quality windows and doors, modern bathrooms and practical interior finishes.

• Premium / Luxury Finish

High-end finishes can significantly increase the overall build cost.

Features such as bespoke joinery, underfloor heating, aluminium glazing systems, smart home technology and luxury bathroom suites all contribute towards a more premium final result.

However, they can also improve long-term property value and create a more luxurious living environment.

Location

Although it can be frustrating, where you live in the UK will also hugely influence your extension costs. 

Labour rates, material availability and local demand all play a role. Let’s break it down by region:

• London And The South East

Construction costs in these areas are generally the highest in the UK.

Labour costs are often significantly more expensive, and increased demand for experienced tradespeople can push prices up even further.

• The North

Homeowners in Northern regions often benefit from more competitive labour and construction pricing.

This can make a substantial difference when budgeting for larger projects, such as two-storey extensions.

• The Midlands

The Midlands also tends to offer excellent value for money compared to the South of England.

Local availability of experienced contractors can help keep pricing competitive while still delivering high-quality workmanship.

While online estimates and double-storey extension cost calculators can provide a useful starting point, the best way to understand realistic pricing in your area is to speak directly with an experienced local builder – like us here at West Midlands Building Company.

Benefits of Adding a Double Storey Extension

A double storey extension isn’t simply about adding more square footage – it’s about improving the way your home works for your lifestyle.

Still deciding whether the investment is worthwhile? Here are some of the biggest advantages homeowners often experience:

• More living space: Two-floor extensions allow you to gain additional bedrooms, bathrooms, offices or larger family areas without sacrificing too much garden space.
• Increased property value: A well-designed two-storey extension can significantly improve your home’s market value and appeal to future buyers.
• More cost-effective than moving: When you factor in estate agent fees, stamp duty and moving costs, extending your existing home can often be the more practical financial decision.
• Better use of your property: Two-storey extensions maximise the available footprint of your home while improving overall layout and functionality.

Double Storey Extension Costs FAQs

How Much Will My Double-Storey Extension Cost?

Every project is different, which is why getting a personalised quote is always the best option. This detailed quotation should include:

• Materials
• Labour
• Structural work
• Design and planning considerations
• Finishing costs

At West Midlands Building Company, we provide free, no-obligation quotes so you can fully understand your project costs from the outset with no pressure. 

How Much Would a Two-Storey Extension Cost In My Area?

It’s important to remember that location has a major impact on pricing across the UK. In simple terms:

• London and the South East → higher costs
• Midlands and Northern regions → more competitive pricing

If you’re based in Birmingham or the West Midlands, you’re often in a strong position to achieve excellent value for money compared to other parts of the UK – especially with competitive prices as you’d find at West Midlands Building Company.

Do I Need Planning Permission for a Double-Storey Extension?

In most cases, yes. Unlike many smaller extensions, double storey extensions usually require planning permission due to their height and impact on neighbouring properties.

However, requirements can vary depending on your property type, location and proposed design, so it’s always best to seek professional guidance (like us!) before starting.

How Long Does a Double Storey Extension Take?

On average, most double storey extensions take between 6–12 months to complete from start to finish.

The exact timeline depends on the complexity of the project, weather conditions, planning approval and the specification of the build. It’s good to note that larger or more bespoke projects may naturally take longer.

Ready to Build Your Double Storey Extension?

Now that you have a clearer understanding of how much a double storey extension costs and the factors that influence pricing, you’re ready to start planning your dream home!

Whether you’re still exploring ideas or ready to begin building, putting your faith in the right team is essential. Here at West Midlands Building Company, we combine experience, transparency and craftsmanship to deliver high-quality extension projects tailored to your home and lifestyle.

We’ve completed hundreds of extension projects across Birmingham and the wider West Midlands area. With more than 150 positive Google reviews, we’ve built a reputation as one of the region’s most trusted and customer-focused building companies.

We also offer a range of finance options, including buy-now-pay-later plans, and at the time of writing, we’re the only provider in the West Midlands offering finance terms of up to 20 years on conservatory projects.

Ready to start your two-floor extension project? Get in touch with one of our friendly team members today for a FREE quote and expert advice on the next steps.

Related Articles:

Double-Storey Extension Ideas

Do You Need Planning Permission for a Double Storey Extension?

How Long Does It Take To Build a Double Storey Extension?