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How much does a house extension cost in North London?

House extensions in North London can vary widely in cost depending on the size, complexity, and finishes of the project. However, JMB Design And Build North London’s general guidelines and average costs that can help homeowners budget effectively.

J.M.B Design and Build LTD completed house extension project.
This is one of many J.M.B Design and Build LTD house extension projects.

1. Factors Influencing Cost

Several key factors impact the cost of a house extension:

  • Size of the Extension: Larger extensions naturally cost more due to the increased materials and labour required.

  • Type of Extension: Single-storey, double-storey, side return, rear extension, and wrap-around extensions each have different cost implications.

  • Quality of Materials: High-end finishes and materials will significantly increase costs.

  • Structural Complexity: Projects involving extensive structural changes or challenging site conditions (e.g., uneven ground or restricted access) can increase costs.

  • Planning Permissions and Regulations: Obtaining necessary permissions and ensuring compliance with building regulations can add to the overall expense.

  • Professional Fees: Architects, structural engineers, and project managers contribute to the total cost.

2. Average Costs

Here are some typical costs associated with different types of house extensions in North London:

  • Single-Storey Extensions:

  • Basic: £30,000 - £50,000. This includes standard finishes and basic amenities.

  • Mid-Range: £50,000 - £70,000. This allows for better quality materials, bespoke elements, and additional features like bi-fold doors.

  • High-End: £70,000 - £100,000+. This includes premium materials, high-end finishes, and extensive customisation.

  • Double-Storey Extensions:

  • Basic: £50,000 - £80,000. This covers additional rooms with standard finishes.

  • Mid-Range: £80,000 - £120,000. This allows for higher quality materials and finishes.

  • High-End: £120,000 - £200,000+. This includes luxury finishes and significant customisation.

J.M.B Design and Build LTD digging the foundations for a double storey house extension.
J.M.B Design and Build LTD digging the foundations for a double storey house extension.

  • Side Return Extensions:

  • Typically cost between £50,000 and £100,000, depending on the size and finishes.

  • Rear Extensions:

  • Basic: £30,000 - £60,000. Suitable for adding a kitchen or living space.

  • Mid-Range: £60,000 - £90,000. Allows for better materials and more complex designs.

  • High-End: £90,000 - £150,000+. Includes premium finishes and larger spaces.

  • Wrap-Around Extensions:

  • Costs range from £80,000 to £200,000+, depending on the overall size and level of finish.

3. Additional Costs

  • Professional Fees: Architects and engineers typically charge between 5% and 15% of the total project cost.

  • Planning and Building Regulations: Planning permissions and building regulation approvals can cost between £500 and £2,000.

  • Contingency Fund: It's advisable to set aside 10-20% of the total budget for unexpected costs.

4. Cost-Saving Tips

  • Detailed Contracts: Ensure contracts cover all aspects of the work to avoid hidden costs.

  • Prioritise Needs: Focus on essential features and finishes to stay within budget.

  • DIY Where Possible: Consider doing some non-specialist tasks yourself to save on labour costs.

J.M.B Design and Build LTD have successfully completed countless extensions in North London.
J.M.B Design and Build LTD have successfully completed countless extensions in North London.


House extensions in North London are a substantial investment that can significantly enhance living space and property value.

By understanding the costs involved and planning carefully, homeowners can ensure a successful and cost-effective extension project, JMB Design And Build Service North London and are at hand to discuss all your requirements.

Are you looking for a house extension in North London? Speak with JMB Design And Build North London today, we have a wealth of knowledge and an extensive portfolio and we cover North London and all surrounding towns and boroughs.


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