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How much does an extension cost?

UK Home Improvement

How Much Does an Extension Cost?

Home extensions are a great way to add more space to your home. The ideal solution to many space-saving issues, it is usually more cost-effective than moving house.

However, one of the first questions homeowners will inevitably ask is ‘how much does an extension cost?’ 

The cost of a home extension can vary widely depending on several factors, from the type of extension you want to build to the materials you choose. In this article, we’ll break down everything you need to know about extension costs providing you with all of the information to keep you fully informed. 

Read on to find out more…

Benefits Of A Home Extension 

Before diving into the costs, let’s take a look ar some of the benefits having an extension built can bring. There are a wide range of reasons you should consider a home extension including:

Additional living space: A home extension can provide you with much-needed extra room by adding a new bedroom, kitchen or living space. This is perfect if you’re planning to grow the family or simply want more usable space without relocating.

Increase property value: A well-executed extension can significantly boost your property’s market value. Prospective buyers often view extra square footage as a major selling point, which can help you get a higher return on investment when it’s time to sell.

Avoid the hassle of moving: Moving house can be costly and stressful, and many people avoid this if they can. Instead, extending your existing home allows the space to be tailored to your exact needs without dealing with the inconvenience of moving to a new property.   

Customisable design: An extension also gives you the freedom to design a space that fits your exact requirements. From open-plan kitchens to home offices that make home working a breeze, the possibilities are endless

How Much Does An Extension Cost?

The cost of a home extension can vary significantly depending on factors such as size, location and finishes. 

On average, you can expect to pay around £1,500 to £2,500 per square metre of new internal space. For example, a new 30m2 kitchen extension will likely fall between £45,500 to £67,500. 

This excludes VAT which will add around 20% to all labour and materials, and higher-end finishes, bespoke designs and added complexity may see your project exceed the average costs. 

One of the biggest factors that will determine the cost of your extension is the type of extension that is being built.

Single Storey Extension Costs 

The most simple and straightforward extension type, the average price of around  £1,500 to £2,500 per square metre is usually a good rule of thumb to follow. 

This price will fluctuate depending on the part of the UK you’re based and the quality of the work.

For example:

  • Standard quality: £1,500 to £1,750 per square metre 
  • Good quality: £1,700 to £2,100 per square metre 
  • Excellent quality: £1,800 to £2,500 per square metre 

Double Storey Extension Costs 

While you may think a double storey extension will cost twice as much as a single extension due to the fact that two floors are being built rather than one, this isn’t actually the case.

In fact, it may cost slightly less as other than the extra interior fittings, only walls and floor joists are being added. The average cost of this kind of extension is around £1,500 to £2,450 per square metre.

The bigger the project, usually the lower the price per square metre you can expect to pay. This includes the following:

  • Standard quality: £1,500 to £1,700 per square metre 
  • Good quality: £1,650 to £2,050 per square metre 
  • Excellent quality: £1,750 to £2,450 per square metre 

Side Extension Costs 

As the name suggests, side extensions are built in the available space at the side of a property. 

These extensions are more complex to build than single or double storey extensions, and you can expect to pay between £2,250 to £2,500 per square metre. The scope of internal work, including reconfiguring utilities like plumbing, factors heavily in the costs of this extension type.

How Are Extension Costs Calculated?

The cost of a home extension is determined by a wide range of considerations. We will go into detail regarding the specific factors that can play a part but the main things that your contractor will use to calculate how much it will cost you include the following:

Labour costs: Builders, contractors and tradespeople needed to work on the project will contribute to the overall cost.

Materials: The type and quality of the materials purchased for the build will impact the price. 

Design and professional fees: Any architects, structural engineers and planning consultants used will charge fees for designing and overseeing the project. While using an architect is not mandatory, it is highly recommended. 

Permits and planning permission: If you need planning permission for your project, you will have to pay a fee.

Additional features: Specific features like underfloor heating, bespoke joinery or high-end fixtures will add to the overall cost.

Site conditions: If your site has accessibility challenges, uneven ground or any other issues they may incur a cost to rectify. 

Factors That Impact Extension Costs

As previously mentioned, the final cost of a home extension will dramatically differ depending on a number of factors. This can be broken down into a few key areas:

Type of extension 

The type of extension will significantly affect the price. The most common types include:

  • Single storey extensions: The most straightforward and cost-effective option, often used for kitchen or living room extensions. The costs range from £1,500 to £2,500 per square metre.
  • Double storey extension: While they can be more expensive upfront, they can actually end up being cheaper when being calculated by square metre. These costs range from £1,500 to £2,450 per square metre. 
  • Side extensions: These extensions are a bit more complicated to construct than other extension types, and the average cost ranges from £2,250 to £2,500 per square metre.

In addition to actually extending the property, there are alternatives such as conversions which can be a cheaper alternative. Loft conversions typically cost between £1,000 to £2,500 per square metre and garage conversions range from £700 to £1,500 per square metre.

Area / location 

Your location will also play a critical role in determining the cost of an extension. Extensions in London and the South East of the country will likely cost more money due to higher labour and material expenses in these regions.

Rural areas may also be cheaper than urban areas, and the specific part of the property that is being worked on can also have an impact. 

Materials 

The quality and type of materials used for your extension will impact the cost:

  • Standard materials: Basic bricks, concrete and standard fixtures are cost-effective choices.
  • Premium materials: Natural stone, glass walls or bespoke finishes can drive up the cost but enhance the project’s aesthetics. 
  • Eco-friendly materials:  Sustainable options like energy-efficient windows or additional insulation may cost more initially but they offer long-term cost savings. 

Size 

The larger the extension, the higher the overall cost. However, the cost per square metre often decreases as the size increases due to factors like fixed costs being spread over larger areas.

How To Save Money On An Extension 

It’s true, home extensions can be expensive.

But, there are a variety of ways to keep costs under control without compromising on quality. 

Some tips to save money include:

Set a realistic budget: From the outset, establish a clear budget and make sure it is communicated to your builder and contractor. Make sure to include a contingency fund of around 10% to 15% for any unexpected costs. 

Opt for a simple design: Complex designs such as curved walls or bespoke finishes can quickly add up the cost. A straightforward, rectangular layout is often more affordable to build. 

Reuse your existing structures: If possible, convert the existing spaces like garages or lofts instead of building entirely new structures. 

Source materials wisely: Take the time to shop around for materials to ensure you’re getting the best price possible. You may also be able to reclaim second-hand options and the builder you’re using might have trade discounts you can make use of.

Do the work yourself: While it’s unlikely that you’ll be able to build an entire extension yourself, if you have the skills taking on tasks like painting, decorating or demolition can save you money on labour costs. 

Work with trusted contractors: Hiring a reputable builder who has transparent pricing can help you avoid hidden fees down the line. 

How long does a home extension take?

Much like the cost of an extension, the timeline will depend on factors like the size, type and complexity of the extension.

Generally speaking, the average timeline is as follows:

Single storey extensions: 12-16 weeks from design to completion, construction will take eight to ten weeks.

Double storey extensions: 20-24 weeks from design to completion, with construction taking 14-16 weeks.

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