The Ultimate Guide to Storey Extensions: Understanding Double Storey Extension Costs and House Extension Costs in 2024

Planning a two-storey side extension can be an exciting and rewarding project. Whether you need more space for a growing family, a home office, or simply want to increase the value of your home, building a two-storey extension is a great way to achieve that. However, understanding the cost of building a double-storey extension and the factors that influence it is essential for budgeting and planning.

In this article, we will explore the average cost of a two-storey side extension in 2024, the various factors that can impact the build cost, and how you can ensure your project complies with building regulations. We’ll also cover some tips on how to keep costs down and maximise the value of your extension.

What is a Two-Storey Side Extension?

A two-storey side extension is a popular type of house extension where additional living space is added to the side of an existing property. This kind of extension is ideal for homeowners looking to expand their living space without compromising their garden area, unlike what might happen with a rear extension. A two-storey extension increases the overall footprint of your home by adding rooms to both the ground and first floors. Common uses for the extra space include creating additional bedrooms, bathrooms, a home office, or even a larger kitchen.

A side extension is often preferred by homeowners because it makes efficient use of space that is typically underutilised on the side of the property. Adding a double-storey extension can dramatically improve the flow of your home, offering open-plan living areas, extra storage, or even a larger lounge area. The flexibility of a two-storey extension allows you to tailor the design to suit your family's specific needs.

However, when planning any type of two-storey extension, it's crucial to ensure that the extension is built in compliance with local building regulations. These regulations ensure the structural integrity, safety, and energy efficiency of the build. Furthermore, the extension must meet local planning permissions and guidelines, which vary depending on the area and type of extension being constructed. Proper planning and adherence to these guidelines will help avoid legal issues and ensure the extension adds value to your home.

Average Cost of a Two-Storey Side Extension in 2024

The cost of a two-storey side extension can vary greatly depending on several factors, such as the size of the extension, location, materials used, and the complexity of the project. In 2024, the average cost to build a two-storey extension typically ranges from £1,500 to £2,500 per square metre. This means that for a 40 square metre extension, the total cost could be anywhere from £60,000 to £100,000.

However, it's important to note that the total extension cost will depend on the specific details of your project. For instance, if you’re adding luxury finishes, bespoke features, or complex structural work, the cost could increase significantly. Additionally, location of your extension plays a major role in the overall price. For example, building costs in London and the South East are generally higher than in other parts of the UK, due to higher labour and material costs.

When calculating the cost per square metre, it’s also important to include additional expenses such as architect fees, planning permission, and compliance with building regulations. These can add an extra 10-15% to your total build cost. It’s advisable to use a house extension cost guide or an extension cost calculator to get a better idea of the total expense for your specific project.

Factors Influencing the Cost of a Two-Storey Extension

Several factors can impact the cost of building a double-storey extension in 2024. Understanding these factors can help you plan and budget more effectively for your extension project.

1. Size of the Extension

The size of the extension is one of the primary factors influencing the build cost. A larger two-storey extension will naturally require more materials and labour, which increases the overall cost. The cost per square metre gives a rough guide to estimate the total expense, but remember that larger projects often come with additional complexities, such as structural reinforcements, which can add to the final bill.

2. Location of the Property

The location of your extension plays a critical role in determining costs. In areas like London or the South East, where labour and materials are more expensive, the overall extension cost will be higher. In contrast, building a double-storey extension in the North of England, Scotland, or Wales tends to be less expensive. The price can vary significantly depending on your location, so it’s important to get quotes from local builders to get a more accurate estimate.

3. Quality of Materials

The materials you choose for your two-storey extension will have a major impact on the total build cost. High-end materials, such as premium bricks, custom windows, or luxury roofing, will increase your expenses, while opting for more standard, affordable materials can help keep costs down. Additionally, the choice of interior finishes—such as flooring, kitchen fittings, and bathroom fixtures—can also significantly affect the overall cost of building a double-storey extension.

4. Compliance with Building Regulations

Any two-storey extension must comply with building regulations, which are designed to ensure the safety, energy efficiency, and structural integrity of the new build. Compliance with these regulations can add to the total extension cost, particularly if additional insulation, fire safety measures, or structural reinforcements are required. Failure to meet these regulations can lead to costly delays, fines, or even the need to redo parts of the work, so it’s essential to factor these costs into your budget from the outset.

5. Planning and Design Costs

Before construction begins, you will need to hire an architect or a designer to draw up the plans for your two-storey extension. Architect fees typically range between 5-10% of the total project cost, and these professionals will help ensure that your extension design is functional, aesthetically pleasing, and compliant with local planning rules. Additionally, you may need to pay for planning permission, which can add to the overall house extension cost.

How to Calculate the Cost of a Two-Storey Extension

Calculating the cost of a two-storey extension requires a clear understanding of the build cost per square metre and the specific details of your project. One of the most effective ways to estimate your expenses is to use a house extension cost guide or an extension cost calculator, which can help you collate the total cost based on the size, design, and location of your extension.

Start by determining the square footage of your planned extension and multiplying it by the average cost per square metre for your region. For example, if your two-storey extension is 40 square metres and the cost per square metre is £2,000, the base build cost would be around £80,000. Be sure to factor in additional costs such as architect fees, VAT, and any unexpected expenses that may arise during the construction process.

It’s also important to include a contingency fund in your budget—typically 10-15% of the total cost—to cover any unforeseen issues, such as changes in the scope of work or unexpected delays.

How to Reduce the Cost of a Two-Storey Extension

Building a two-storey extension can be a significant financial investment, but there are several strategies you can use to manage costs without compromising on quality. One effective approach is to keep the design of your extension simple and avoid unnecessary customisation. The more complex the design, the higher the cost, so sticking to a straightforward layout can help reduce both material and labour expenses.

Additionally, choosing standard, readily available materials instead of opting for bespoke or high-end options can make a big difference in the total build cost. Standard windows, doors, and flooring options are often more affordable and still offer a high-quality finish.

Another cost-saving strategy is to plan your extension around existing plumbing and electrical systems. For example, if you’re adding a new bathroom or kitchen, positioning it near existing plumbing can reduce the cost of rerouting pipes or wiring, which can be expensive.

Lastly, ensure that your builder provides you with a detailed breakdown of the extension cost and stays within the agreed-upon budget. Having clear communication with your contractor and avoiding mid-project changes will help you avoid unexpected cost increases.

Benefits of a Two-Storey Extension

A two-storey side extension offers numerous benefits that go beyond simply adding more space to your home. Firstly, it can significantly increase the value of your home, particularly if the extension is a great way to add extra bedrooms, bathrooms, or a larger kitchen. Homes with additional living space are typically more attractive to potential buyers, which can provide a good return on your investment.

In addition to boosting your home’s value, a two-storey extension can enhance your day-to-day living by improving the flow of your home, adding more natural light, or creating open-plan living areas. It also allows you to maximise the use of your property’s available space, making it more functional and enjoyable for you and your family.

Finally, a double-storey extension often provides more value per square metre compared to a single-storey extension, as it increases both the ground floor and first floor space, giving you a greater return on investment.

Conclusion: Is a Two-Storey Extension Worth the Investment?

Building a two-storey side extension in 2024 can be an excellent investment, offering not only additional living space but also the potential to significantly increase the value of your home. A well-planned two-storey extension provides extra functionality, whether you're adding bedrooms, bathrooms, or expanding your kitchen. However, before starting your project, it is essential to carefully plan and budget, taking into consideration several key factors such as the size of the extension, the location of your extension, the quality of materials, and adherence to building regulations.

Working with experienced extension builders is crucial to ensure that the project runs smoothly and that the final result is both practical and aesthetically pleasing. Calculating the cost per square metre is a vital part of the budgeting process, helping you get a clear understanding of the overall build cost. It's also important to ensure that your extension complies with building regulations to avoid any legal complications or delays.

If you're considering a two-storey extension, now is the perfect time to start planning your project for 2024. By ensuring that your extension is designed to meet your needs while enhancing the value of your home, you can make this investment a success. A two-storey extension is a great way to transform your property, and with careful planning, it can provide long-term benefits for both your lifestyle and your home’s resale value.