What is the cost of building an extension in London?

The cost of building an extension in London can vary significantly depending on several factors, including the size and complexity of the project, the location, the materials used, and the contractor's rates. To provide a rough estimate, here are some general cost ranges for building an extension in London:

1. Single-story rear extension:

- Small (up to 15 square meters): £20,000 - £35,000

- Medium (15-30 square meters): £35,000 - £50,000

- Large (over 30 square meters): £50,000 - £70,000

2. Double-story rear extension:

- Small (up to 15 square meters): £40,000 - £60,000

- Medium (15-30 square meters): £60,000 - £80,000

- Large (over 30 square meters): £80,000 - £100,000

3. Side return extension:

- Small (up to 10 square meters): £15,000 - £25,000

- Medium (10-20 square meters): £25,000 - £40,000

- Large (over 20 square meters): £40,000 - £60,000

4. Loft conversion:

- Basic loft conversion (no bathroom): £30,000 - £50,000

- Loft conversion with bathroom: £50,000 - £70,000

- Luxurious loft conversion: £70,000 - £90,000

5. Basement conversion:

- Small basement conversion (up to 50 square meters): £60,000 - £80,000

- Medium basement conversion (50-100 square meters): £80,000 - £100,000

- Large basement conversion (over 100 square meters): £100,000 - £120,000

It's important to note that these cost ranges are approximate and can vary significantly based on specific requirements and market conditions. It's always a good idea to consult with an architect, surveyor, or contractor who can provide a more accurate estimate based on your project details. Additionally, it's essential to factor in other expenses such as planning permission fees, building regulations approval, and interior finishes, which can add to the overall cost of your extension.