What Is The Average Cost For a Single Storey Extension?

Published On: 3 March, 20266.8 min read

Looking into extending your home, but keen to learn the average prices of one storey extensions first? You’ve come to the right place…

If you’re feeling a bit tight for space but love your home and location, you’re not alone. The prospect of moving is daunting – plus, extremely expensive these days.

In fact, many homeowners across the West Midlands reach a point where moving feels like too much upheaval, but staying put means needing more room.

So the big question is: what is the average cost of a single storey extension, and is it worth the investment for you and your family?

Understanding the single storey extension cost UK homeowners can expect helps you plan realistically, avoid surprises and decide whether now is the right time to build. 

That’s why we here at West Midlands Building Company have created this handy guide to answer all your questions about single storey extension prices, including factors that determine the costs, prices by extension type and how to know when to build. Let’s get down to it…

What Is A Single Storey Extension?

Firstly, let’s define exactly what a single storey extension is. 

A one floor extension is a ground-floor addition built onto the side, rear or (less commonly) the front of a property, and is one of the most popular home improvement projects in the UK.

So, why could your home need a single storey extension? Homeowners often use single storey extensions for:

  • Open-plan kitchen and dining extensions
  • Utility rooms or boot rooms to reduce clutter
  • Living room expansions for growing families
    Downstairs bathrooms or shower rooms
  • Light-filled, garden-facing family rooms
  • …and, basically, whatever you want!

In short, a single storey extension gives you more room to breathe without the upheaval of moving house, and for likely a fraction of the cost.

How Much Does A Single Storey Extension Cost In The UK?

So, let’s talk numbers – what is the average cost of a single storey extension?

Here at West Midlands Building Company, our average cost of a single storey extension for a typical 3m x 3m build starts from around £30,000–£40,000. 

While this is a realistic benchmark for homeowners in today’s market, there is no one-size-fits-all figure. A one storey extension cost can rise or fall depending on design choices, site conditions and the finish you’re aiming for.

What Determines The Average Cost Of A Single Storey Extension?

While it’s good to have a benchmark, your actual cost of one storey extension would be influenced by several core factors – and the details are where costs really take shape.

Key factors include:

  • Size: Larger extensions naturally cost more due to increased materials, labour and time. Even an extra metre can significantly affect the final figure, so it’s important to be clear about your requirements.
    Type of Extension: The type of extension you choose also has a huge bearing on the cost. For example, the cost of a single-storey rear extension is usually more straightforward, while wraparound designs are more complex and therefore, often more expensive.
  • Groundworks Required: Poor soil conditions, drainage changes, or deep foundations can lead to unexpected costs early in the project.
  • Quality Of Fittings And Fixtures: A basic finish keeps costs down, which is great for utility rooms or boot rooms, while premium kitchens, bespoke joinery, or luxury bathrooms can push budgets up.
  • Location: Build costs vary across the UK, so location is important to consider. Luckily, in the West Midlands, prices are generally more affordable than in London or the South East, but they still depend on access and local labour availability.

Additional Factors That Determine Costs Of A One Storey Extension

Beyond the core build, several additional elements influence the single storey extension cost UK homeowners should budget for. These include:

  • Timescales: How quickly you want your single storey extension built can actually affect your overall price. Faster builds often require more labour at once, which can increase costs.
  • Labour Costs: Equally, skilled trades come at a premium (and rightly so!), so you may find costs arise with higher-quality labourers. But, not to fear – quality workmanship saves money long-term.
  • Site Survey: Surveys help identify issues early, reducing the risk of costly surprises mid-build, but are often forgotten when accounting for extension costs.
  • Architect Fees: Similarly, architects may be a forgotten cost, too. Good design maximises space, light, and value, but architectural input does add to the overall cost.
  • Planning Applications & Building Regulations: Before you can even begin building, you’d have to pay out for single storey extension planning permission and building regulations. Even permitted development projects still require building control approval and inspections.
  • Materials: From bricks and insulation to steelwork, material choice affects both cost and performance – so choose wisely!
  • Doors & Glazing: Bi-fold or sliding doors are popular, but they do cost more than standard options, so door selection is important to account for in your budget.
  • Flooring: Similarly, tiles, engineered wood or underfloor heating all carry different price points, too.
  • Heating & Electrics: Extending existing systems or installing new ones impacts the budget, especially if the room is a totally new standalone space.
  • Style of Room: Equally, the style of a room has a significant bearing on the overall price. A minimalist utility room costs far less than a high-spec kitchen-diner designed for entertaining.
  • Individual Tradesmen Costs: And, of course, plumbers, electricians, plasterers and decorators all contribute separately to the final price.

How Much Does A Roof Cost For A Single Storey Extension?

Roof choice plays a big role in both appearance and budget – typical costs include:

  • Flat Roof: £3,000–£6,000

Flat roofs are cost-effective and modern, especially with high-quality membranes, so a great choice for those on a smaller budget.

  • Pitched Roof: £5,000–£10,000

A more traditional style roof, pitched roofs are excellent for blending with existing homes, and perfect for mid-range budgets.

  • Glazed Roof Or Roof Lantern: £6,000–£12,000+

Ideal for bringing in natural light, glazed roofs or lantern roofs are a popular, modern choice, but are higher in cost due to specialist materials.

But remember, choosing the right roof isn’t just about price – it’s also about how you want the space to be used every day. Want a light flooding modern space to marvel at each morning? The lantern roof may well be your go-to.

Single Storey Extension Costs UK FAQs

What’s The Average Cost Of A Single Storey Rear Extension?

The average cost of a single storey rear extension typically ranges from £30,000–£50,000, depending on size, finish, and structural complexity.

What’s The Average Cost Of A Single Storey Wraparound Extension?

A wraparound extension is more complex and usually costs £50,000–£80,000+ due to increased structural work and larger floor area.

What’s The Average Cost Of A Single Storey Front Extension?

Front extensions are less common and often require planning permission. Costs typically start from £35,000, depending on design and approval requirements.

What’s The Average Cost Of A Single Storey Side Extension?

A single storey side extension generally costs £35,000–£60,000, influenced by access, drainage and whether it’s combined with a rear extension.

What’s The Least Expensive Type Of Single Storey Extension?

In summary, a small rear extension with a flat roof and standard finishes is usually the most cost-effective option – perfect if you want maximum impact of a brand new space without stretching the budget too far.

Ready To Start Building Your Single Storey Extension?

Here at West Midlands Building Company, we’ve worked on hundreds of single storey extension projects in the Birmingham and West Midlands area. With over 150 positive Google reviews, we’ve built a reputation as one of the most reliable and customer-focused companies in the region. 

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

Ready to start your home improvement journey with a single floor extension? Get in touch with one of our friendly team members today to receive a FREE quote, and information about next steps.