Thinking about adding more space to your home with a rear extension? At Oakstead Construction, we know that one of the first questions homeowners ask is: how much will it cost in Tonbridge & Malling?

 While the answer can vary based on size and specification, this guide breaks down the typical costs and what factors influence them—so you can plan your dream project with confidence.

Average Cost of a Rear Extension in the UK (2025)

As of 2025, the cost of a single-storey rear extension in the UK generally ranges from:

£1,800 – £2,500 per square metre for a basic-quality finish

£2,500 – £3,000+ per square metre for a high-end specification

Here’s what that might look like in practice:

Extension Size

Estimated Cost (Standard Finish)

3m x 4m (12m²)

£27,500 – £40,000

4m x 5m (20m²)

£40,000 – £60,000

6m x 5m (30m²)

£60,000 – £85,000

Note: These figures are for construction costs only. Design fees, planning permissions, and VAT (if applicable) should also be factored in.

Key Factors That Influence the Cost

Size and Layout
Larger extensions cost more, but also offer better value per square metre. A complex layout or open-plan design may require additional structural support, increasing the price.

Location
Building in London or the South East tends to cost more due to higher labour and material costs.

Level of Finish
Choices such as underfloor heating, bi-fold doors, or custom kitchens can significantly raise the overall budget.

Planning and Regulations
While many rear extensions fall under permitted development, some may require planning permission or party wall agreements, adding to the timeline and cost.

Access and Site Conditions
Limited access to the rear of your property or difficult ground conditions can increase labour time and machinery requirements.

What’s Included in the Price?

At Oakstead Construction, our rear extension projects typically include:

Foundations and structural works

Brick/blockwork and roofing

Windows and doors

First fix electrics and plumbing

Internal plastering and finishes

Flooring and basic decorating

We also offer project management from start to finish—so you're never left in the dark.

How to Budget for Your Rear Extension

Here are a few budgeting tips to keep your project on track:

✅ Always include a 10–15% contingency for unforeseen costs
✅ Get a detailed quote—not just a ballpark figure
✅ Work with trusted contractors who are transparent about pricing
✅ Plan your design early to avoid costly changes mid-project

Thinking About a Rear Extension? Let’s Talk.

A rear extension can transform your home and the way you live in it. Whether you're looking to create a spacious kitchen-diner, a bright family room, or simply want to add value to your property—Oakstead Construction is here to help.

Ready to start your project?
Contact us today for a free consultation and quote tailored to your home and budget.

📞 07940249027
📧 contact@oaksteadconstruction.co.uk
🌐 www.oaksteadconstruction.co.uk