3m X 3m Extension Cost

Trying to find out how much it costs for a House Extension? Try our FREE online Calculator and get a quote in under 2 minutes for your project. Our free extension cost calculator provides a quick, personalised estimate in 60 seconds. Explore costs based on your extension size and needs.

That's where our free extension cost calculator can help you. By answering questions about your build in a few simple steps, our extension cost calculator will use the information provided to build a quote for you, based on the information you provide. This calculator helps you estimate the total cost of an extension project based on various parameters like length, width, height, and material and labor costs per square meter.

How to Use the House Extension Cost Calculator To calculate the cost of extending your house, follow these steps: Enter the area of the extension in square meters. Select the type of flooring, wall finish, and roof. Enter the number of windows and doors you want in the extension.

Check the box if you'd like to include a $2000 cost for necessary approvals. Enter the percentage for labor costs. Discover our extension cost calculator.

So, the total cost for a single-storey house extension would be around £54,000+. Cost of a Double-Storey Extension (Same Footprint) For a double-storey extension with the same footprint (4m x 5m), you can generally add 50% to the build cost of a single-storey extension. This would break down as follows: Build Cost: £40,000 + 50% = £60,000.

Extension cost calculator. Work out your instant price estimate here. Our price sharing community help you find out what others are paying before you contact tradespeople.

What's the average cost of a house extension in 2025? Read the latest cost guidance from Checkatrade. How much does a house extension cost in 2025? The prices in this guide are accurate as of 2025* Average installation and materials costs for a house extension A home extension can add value to your home.