How much does a house extension cost in 2024/25?

Factors Affecting Extension Costs

While the average cost per square meter provides a general estimate, several factors can significantly impact the overall cost of your house extension:

1. Type of Extension: The type of extension you choose will affect the cost. Single-storey extensions are generally less expensive than double-storey or wrap-around extensions.
2. Quality of Finish: The quality of materials and finishes you select can greatly influence the cost per square meter. Basic finishes may cost £1,000 – £1,700/m², while high-end finishes can range from £1,900 – £2,200/m² for a single-storey extension.
3. Location: Extension costs can vary depending on your location, with higher prices typically found in areas like London and the surrounding regions.
4. Complexity of Design: Intricate designs, unique shapes, or challenging site conditions can increase the overall cost of your extension project.

Additional Costs to Consider

Beyond the construction costs, there are several additional expenses to factor into your budget:

• Architectural and design fees
• Planning permission and building regulation fees
• Structural engineering costs
• Site preparation and groundworks
• Utility connections (e.g., plumbing, electrical)
• Landscaping and exterior work

Cost Calculation Example

To illustrate the potential costs, let’s consider a 25m² single-storey extension with good quality finishes in an average location:

• Construction cost: 25m² x £1,800/m² (average for good quality) = £45,000
• Architectural fees: Approximately £3,000 – £5,000
• Planning and building regulation fees: Approximately £1,000 – £2,000
• Additional costs (e.g., groundworks, utilities): Approximately £5,000 – £10,000

Total estimated cost: £54,000 – £62,000 (excluding VAT)Keep in mind that these are rough estimates, and actual costs may vary based on your specific project requirements and location.