How Much Does a House Extension Cost?

As we grapple with our growing needs and changing lifestyles, the idea of expanding our homes can be an appealing one. The addition of an extra room, an expanded kitchen, another bathroom or a brand-new conservatory can add valuable living space and potentially increase the value of our homes. But the question that often arises is, how much does a house extension cost? In this article, we take a look at typical house extensions, their associated costs, and the critical factors to consider, such as planning permission and potential escalating costs.

Typical House Extensions

A house extension can take various forms depending on your home’s layout, your budget, and your specific needs. Some popular types of house extensions include:

1. Single-storey extensions: These are typically added to the back or side of the house, expanding living areas, kitchens, or adding an extra ground floor bedroom.
2. Two-storey extensions: These add more than one level, providing extra bedrooms, bathrooms, or home offices.
3. Conservatories and orangeries: These glass and frame structures are a popular way to add a bright, welcoming space to a home.
4. Loft conversions: Transforming an unused loft into a liveable space is a cost-effective way to add an extra bedroom or office.

Costs of a House Extension

The costs associated with a house extension can vary greatly, depending on the type of extension, its size, and the materials used. As a rough guide, here are average costs as of 2023:

1. Single-storey extension: £1,300 to £1,500 per square metre.
2. Two-storey extension: £1,500 to £1,800 per square metre.
3. Conservatory: £5,000 to £30,000, depending on size and design.
4. Loft conversion: £20,000 to £60,000, depending on the complexity of the conversion.

These figures, however, only account for building costs. Additional expenses such as architect’s and structural engineer’s fees and planning permissions, can add another 15% to 20% to the overall cost.

Planning Permissions

Before undertaking any extension, it’s important to understand that you may require planning permission from your local council. Certain types of extensions, such as those that don’t exceed a certain size or height, may fall under “permitted development rights”. However, it’s always wise to check with your local council before starting any work. Failing to do so can result in hefty fines and may even require you to undo the work.

Planning permission typically costs around £200, but this can vary depending on the nature of your project. Keep in mind that obtaining planning permission can also extend your project timeline, as it can take up to 8 weeks for a decision.

Beware of Escalating Costs

When planning a house extension, it’s vital to account for potential unexpected costs. Unforeseen issues, such as structural problems or issues uncovered during excavation or construction, can cause costs to escalate quickly. It’s wise to add a contingency of at least 10% to 20% to your budget to cover these unexpected expenses.

Hiring Professionals

While it might be tempting to manage the project yourself to save costs, hiring professionals can make the process smoother and help to avoid costly mistakes. Architects, surveyors, and builders have the necessary expertise and can offer valuable advice on how to get the most from your extension.

Hiring an architect will typically cost between 7% to 15% of the total build cost. They can help with everything from designing the space to fit your needs, to navigating the planning permission process, and managing the build. A structural engineer, whose fees are usually between £400 and £600, is essential for loft conversions or if you plan to remove any load-bearing walls.

Energy Efficiency

Another factor to consider is the energy efficiency of your new extension. Building regulations require new builds and extensions to meet specific energy efficiency standards, so it’s essential to factor these into your plans. This could involve choosing high-performance insulation, energy-efficient glazing, or even renewable energy sources such as solar panels. While these can add to the upfront cost, they can result in significant savings on your energy bills in the long term.

The Value of an Extension

While the primary purpose of an extension is often to increase living space, it can also add significant value to your home. According to a recent study, a well-executed extension can add up to 23% to a property’s value. However, it’s important to ensure the extension is in keeping with the style of your home and the surrounding properties. A poorly designed or executed extension could detract from your property’s value.

To Extend or Not to Extend?

Ultimately, the decision to extend your home should be based on your current needs, budget, and long-term plans. A well-planned and executed extension can transform your living space and potentially add value to your home. However, it’s crucial to be aware of the costs involved and the potential for unexpected expenses.

Remember to seek professional advice, consider the energy efficiency of your extension, and think about how the changes will fit with your home’s current style. With careful planning and consideration, a house extension can be a worthwhile investment that brings enjoyment and added value for years to come.