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How much do house extensions cost?

Start of a house extension

Your home is more than just four walls; it's a space that evolves with you over time. As your family grows, your lifestyle changes or your needs shift, you may find that your current living space needs a little extra room to breathe.

This is where a home extension comes into play, expanding your living space and enhancing your home's functionality. But how much should you budget for such an endeavour in the UK? Let's delve into the factors that influence the average cost of a home extension and provide you with an answer to the question: How much do house extensions cost?

Types of Home Extensions

The cost of a home extension in the UK varies significantly based on the type of extension you're planning. Common types include:

Single-Storey Extension: Typically the most cost-effective option, these extensions include kitchen extensions, additional living spaces, or even a home office. Costs depend on factors like size, materials, and complexity.

Two-Storey Extension: This option involves extending both the ground and first floors of your home, which can be a substantial project. It's ideal for adding multiple rooms or significantly expanding living space.

Loft Conversion: Converting an attic or loft space into a habitable area is a cost-effective way to add extra rooms or a new living space. Costs can vary based on the amount of work required and the area's intended use.

Basement Conversion: If you have a basement, converting it into additional living space can be a viable option. Costs depend on factors like excavation, structural work, and interior finishes.

Factors Influencing Costs

Location: The cost of a home extension can significantly differ depending on where you live in the UK. London and the South East tend to have higher construction costs than other regions.

Size and Complexity: The larger and more complex the extension, the higher the cost. Factors like the size, shape, and design intricacies play a role.

Materials: Your choice of materials for the extension, such as brick, timber, or uPVC, will affect the cost. High-quality materials tend to be more expensive.

Planning Permission and Building Regulations: Depending on your project's size and type, you may need planning permission, which can incur additional costs. Ensure you're aware of local regulations.

Design and Architectural Services: Hiring an architect or designer can add to your expenses, but their expertise can result in a well-planned, efficient extension.

Utilities and Services: Extending utilities like plumbing and electricity to your new space will impact costs. Consider these requirements in your budget.

Average Costs

According to Checkatrade, the average cost for a 20m2 extension is £48,000, adding 10 - 20% to the value of a home. While no project is the same, and the costs can vary significantly, here are some approximate figures:

Single-storey extension: £1,200 - £2,500 per square meter.

Two-storey extension: £1,500 - £3,000 per square meter.

Loft conversion: £1,000 - £2,500 per square meter.

Basement conversion: £1,500 - £3,000 per square meter.


For an accurate estimate, consulting with builders or contractors who can provide quotes based on your specific project requirements is best. If you need assistance with project management, contact our team today.

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