So, How Much Does a House Extension Cost in 2025?
If you’re planning to expand your living space this year, you’re probably asking: how much does a house extension cost in 2025? While the cost will vary depending on several key factors—such as size, materials, location, and labour—the good news is that extensions remain one of the most effective ways to add space and value to your home.
In this blog, I’ll break down average extension prices in 2025, what influences the overall cost, and how to plan your project realistically while staying on budget.
Average House Extension Costs in 2025
The price per square metre for a house extension in 2025 ranges between:
- £1,400 – £2,000 per m² for a basic finish
- £2,000 – £2,500 per m² for a mid-range finish
- £2,500 – £3,000+ per m² for high-spec or complex builds
This means a 20m² single-storey extension can cost anywhere from £28,000 to over £60,000 depending on specifications and finishes.
Double-storey extensions generally add around 50–75% more to the base cost, as structural work increases but some savings are made on roofing and foundation costs.
Factors That Influence the Cost of a House Extension
1. Type of Extension
There are several types of extensions, and each comes with its own cost profile:
- Rear extensions: Common and often straightforward to build
- Side return extensions: Ideal for semi-detached or terraced homes
- Wraparound extensions: Offer the most space but require more planning and materials
- Double-storey extensions: More complex, but can significantly increase living space and value
2. Location of the Property
Labour and material costs vary by region. In Kent and South East England, prices tend to be slightly higher than the national average due to demand and access to materials.
3. Site Conditions
Restricted access, sloped gardens, tree removal, or poor ground conditions can add significant cost through groundwork and preparation.
4. Materials and Finishes
Your choice of windows, doors, flooring, kitchen fittings, and other finishes has a large impact on total spend. Bespoke or luxury finishes cost more and may also increase labour time.
5. Planning and Permissions
Some projects fall under permitted development rights. Others may need full planning permission, which adds time and cost.
We offer full planning support including drawings, applications, and guidance through the approval process.
Additional Costs to Consider
Make sure to budget for:
- Structural engineer reports (if major changes are involved)
- Party wall agreements (for shared boundary properties)
- Planning application fees
- Upgrades to plumbing, electrical, or heating systems
- New kitchens or bathrooms if included in the build
- Waste removal or landscaping post-build
Our detailed quotes break down these elements, so you’re not caught out by unexpected charges.
How to Budget for an Extension in 2025
1. Get a Detailed Quote Early
Work with a reputable builder who provides a full breakdown of materials, labour, and timelines. This makes it easier to spot where costs can be adjusted if needed.
2. Include a Contingency
Always set aside an extra 10–15% of your budget to cover changes or unforeseen issues during the build.
3. Prioritise Your Needs
Start with what’s essential (e.g., additional living space or bedroom), then scale features depending on your remaining budget.
Is an Extension Still Worth the Cost in 2025?
Yes—despite rising material prices and inflation, extensions remain one of the best ways to increase your home’s usability and long-term value. Compared to the cost of moving (which can exceed £25,000 when you include fees and stamp duty), an extension gives you better control over the end result and avoids the disruption of relocating.
Why Choose Local Professionals for Your Extension?
Working with experienced local builders gives you:
- Faster site access and progress updates
- Better knowledge of local regulations
- Strong supplier relationships that can reduce delays
- Reputation-backed service—see our client feedback on Google My Business and Trust a Trader
We offer full construction and aftercare services to make sure every aspect of your extension meets standards and expectations.
How We Can Help
We’ve supported hundreds of homeowners across Kent with well-managed, cost-effective extension builds. Our services include:
- Complete project management from planning to completion
- Transparent pricing and scope of work
- Tailored designs based on your needs and budget
Contact us here to get a detailed quote and expert advice on your 2025 home extension.