How Much Does It Cost to Extend a House in the UK?

The cost of a house extension in the UK can vary widely depending on several factors, including the location, type of extension, quality of materials, and complexity of the project. However, a general estimate for house extension costs per square meter (m²) can provide a useful starting point.

Typical Costs

Basic Extensions

Cost Range: £1,200 – £1,500 per m²

Description: This range typically covers basic single-story extensions with standard finishes and minimal customisation.

Mid-Range Extensions

Cost Range: £1,500 – £2,500 per m²

Description: Mid-range extensions might include higher-quality materials, more complex designs, and additional features such as bi-fold doors or skylights.

High-End Extensions

Cost Range: £2,500 – £3,500+ per m²

Description: High-end extensions involve luxury materials, bespoke designs, and high-

specification finishes. These projects might also include advanced technologies and premium fittings.

Additional Factors Affecting Costs

Location:

Costs in London and the South East are typically higher than in other parts of the UK due to increased labour and material costs.

Type of Extension:

Single-Story Extension: Generally less expensive and simpler to construct.

Double-Story Extension: More expensive due to additional structural requirements.

Loft Conversion: Costs can vary but often range from £1,200 – £2,000 per m².

Complexity of Design

Simple, rectangular extensions are usually cheaper than those with complex shapes or multiple angles.

Extensions requiring significant structural changes or involving difficult ground conditions (e.g., sloped sites) will also be more expensive.

Quality of Materials and Finishes

Basic finishes (standard kitchen units, basic bathroom fittings) will be cheaper than premium finishes (high-end kitchen appliances, luxury bathroom fittings).

Professional Fees

Fees for architects, structural engineers, and planning applications can add to the overall cost. 

These might range from 10% to 15% of the construction cost.

Permits and Regulations

Costs for planning permission, building regulation approvals, and other legal requirements should also be factored in.

Example Breakdown

For a mid-range single-story extension of 30 m², the estimated costs might be:

Basic Construction Cost: 30 m² x £2,000 = £60,000

Professional Fees (10%): £6,000

Planning Permission: £200 – £500

Building Regulation Fees: £500 – £1,000

Contingency (10%): £6,000

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Total Estimated Cost: Approximately £72,700 – £73,500

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Cost Estimation Tools and Resources

Homebuilding & Renovating Cost Calculator: A useful tool to get a more tailored estimate for your project. Homebuilding & Renovating Cost Calculator

By considering these factors and using estimation tools, you can get a more accurate idea of the potential costs involved in extending your house in the UK.

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The Author does not accept any responsibility for misstatements made or any misunderstandings arising from it.

While every effort has been made to check the accuracy of this article, readers should always make their own checks.  

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