Planning a home extension is an exciting step toward creating more space, boosting property value, and transforming how you live. One of the first questions homeowners ask is: how much does an extension cost per square metre? The answer can vary, but understanding the typical price range—and what influences it—will help you budget confidently and make smarter decisions.

Average Cost Per Square Metre

In the UK, the average cost of a house extension typically falls between £1,500 and £3,000 per square metre. This range depends on the complexity of the project, the materials used, and the level of finish you’re aiming for.

  • Basic extensions (simple design, standard materials): £1,500–£2,000/m²
  • Mid-range extensions (good-quality finishes): £2,000–£2,500/m²
  • High-end extensions (premium design and materials): £2,500–£3,000+/m²

For example, a 20m² extension could cost anywhere from £30,000 to £60,000+, depending on your choices.

What Affects Extension Costs?

Understanding the factors that influence extension cost per square metre can help you control your budget and avoid unexpected expenses.

1. Size and Design Complexity

Larger extensions often reduce the cost per square metre slightly, but intricate designs, unusual layouts, or bespoke features can increase costs significantly.

2. Materials and Finishes

High-quality materials like bi-fold doors, skylights, or luxury flooring will elevate both the look and the price. Choosing cost-effective alternatives can keep your project within budget.

3. Location

Labour and material costs vary by region. Urban areas and high-demand locations often come with higher building costs.

4. Type of Extension

Different types of extensions come with different price points:

  • Single-storey extension – typically more affordable
  • Double-storey extension – better value per m² overall
  • Kitchen extension – often higher due to plumbing and fittings

5. Planning and Professional Fees

Don’t forget additional costs like architectural design, planning permission, structural engineering, and building regulations approval. These can add 10–20% to your total budget.

How to Get the Best Value for Your Extension

If you’re looking to maximise your return on investment while keeping costs manageable, consider these smart strategies:

Choose a Simple Layout

Rectangular designs are more cost-effective than complex shapes, helping reduce both labour and material expenses.

Plan Early and Thoroughly

Detailed planning minimises delays and unexpected costs. Working with experienced professionals ensures your project runs smoothly.

Balance Quality and Budget

Invest in areas that matter most—such as insulation, structure, and natural light—while being flexible with cosmetic finishes.

Is a House Extension Worth the Cost?

A well-designed home extension doesn’t just add space—it can significantly increase your property’s market value and improve your lifestyle. Whether you’re creating an open-plan kitchen, adding an extra bedroom, or building a home office, the right extension can deliver long-term benefits.

Final Thoughts

The cost per square metre for an extension depends on multiple factors, but with the right planning and expert guidance, you can achieve a beautiful and functional space within your budget. By understanding pricing, exploring your options, and making informed choices, you’ll be well on your way to creating a home that truly works for you.

If you’re ready to start your extension project, getting tailored quotes from trusted professionals is the best next step to turn your vision into reality.

Read More: External Wall Insulation Cost Guide 2026