Considering a house extension? It’s one of the most effective ways to create more living space, improve functionality, and increase the value of your home without the stress of moving. Across the UK, extensions are becoming increasingly popular as families grow, lifestyles change, and property prices make relocation less appealing.
At Kova Interiors, we know that understanding the costs involved is the first step to a smooth project. This guide outlines average UK extension costs, explains the key factors that influence pricing, and offers practical advice to help you plan and budget effectively.
Understanding House Extension Costs
1. Average costs of house extensions in the UK
The cost of a house extension in the UK varies depending on its size, design complexity, and purpose. Single-storey extensions typically range from £1,500 to £2,500 per m², while double-storey builds can be £2,000 to £3,000 per m². Specialist spaces such as kitchens or bathrooms tend to be higher due to additional plumbing, electrical work, and bespoke finishes.
2. Typical pricing per square metre (m²) for common extensions
As a general guide, kitchen extensions often fall between £1,750 and £3,500 per m², loft conversions between £1,500 and £2,500 per m², and rear or side return extensions usually mirror single-storey rates. These figures provide a starting point before factoring in the unique details of each project.
3. Brief comparison of costs across different UK regions
Location plays a major role in overall pricing. Extensions in London and the South East can cost a lot more than similar projects in the Midlands or Scotland due to higher labour rates and material expenses. Understanding these regional variations helps ensure budgets are set accurately from the outset.
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Factors Influencing House Extension Costs
Several elements can significantly impact the final price of a house extension, Such as:
1. Size and Type of Extension
The size and intended use of the extension directly affect costs. Double-storey extensions often have a higher total cost than single-storey builds, though the cost per m² can be lower due to shared foundations and roofing. Functional spaces such as kitchens or bathrooms require additional plumbing, electrical, and ventilation work, making them more expensive than living or bedroom spaces.
2. Complexity and Design
The more complex the design, the more time, materials, and specialist expertise will be required. Features such as large glazing panels, intricate roof structures, or bespoke layouts increase the budget. Structural changes like removing load-bearing walls or reinforcing foundations can also add significant costs.
3. Location
Regional differences in labour and material costs play a big role. London and the South East generally have the highest rates, while the Midlands and North tend to be more cost-effective. Urban projects may also face challenges such as restricted access or higher delivery charges, while rural sites might incur increased transportation costs for materials and equipment.
4. Building Materials and Finishes
Material choice is one of the largest cost drivers. Standard finishes help keep costs manageable, while premium options such as hardwood, natural stone, or custom joinery quickly increase the budget. Sustainable or specialist materials may cost more initially, but can deliver long-term benefits in energy efficiency and durability.
5. Labour and Professional Fees
Architects, surveyors, and structural engineers typically account for 10–15% of the overall budget. Skilled trades like builders, electricians, and plumbers also vary in cost depending on location. Hiring an experienced and reputable team like Kova Interiors, is essential to ensure quality and avoid costly mistakes.
Budgeting for Your House Extension
Budgeting for a house extension requires careful planning and a clear understanding of all potential costs. Here’s a structured approach to keeping your project on track:
Step-by-step budgeting tips
- Define your extension’s purpose and size. Our team can visit your property to take accurate measurements for you.
- Request one detailed, all-inclusive quote from us. Our in-house experts cover everything from architectural design to structural engineering and surveying.
- We’ll include any necessary planning permission and building regulation costs in your quote, so there are no hidden surprises.
- All costs will be itemised, including VAT where applicable, giving you full visibility from the start.
Typical hidden or unexpected costs
- Site preparation and demolition
- Upgrades to drainage or utilities
- Temporary accommodation during disruptive works
- Storage for furniture or belongings
- Permit or inspection fees
- Landscaping and external works after the build
Setting aside contingency funds
We recommend reserving a percentage of your total budget for unforeseen expenses. This allows for smooth progress if unexpected issues arise, such as structural repairs, supply chain delays, or changes in material availability. Having this buffer ensures your project stays on schedule and maintains the desired quality without financial strain.
Ways to Save Money on Your Extension
Practical tips for reducing overall costs
1. Keep the design clear and functional to reduce unnecessary labour and material expenses.
2. Retain existing plumbing and electrical layouts where possible to avoid costly relocations.
3. Select durable, cost-effective finishes that achieve the desired look without overspending.
4. Finalise all design and specification decisions before construction begins to prevent expensive alterations.
5. Leverage our supplier network to secure competitive prices on quality materials.
DIY vs. professional help – cost implications
While DIY may seem cheaper, it can lead to poor workmanship, safety hazards, and costly corrections. For structural, electrical, and plumbing work, always use qualified professionals. This ensures compliance with building regulations and protects the long-term value of your home.
Negotiating with contractors
- Request one comprehensive, detailed quote from us that covers all aspects of the extension.
- We offer fixed-price agreements where possible to give you full budget certainty.
- All payment schedules and milestones are agreed upfront for complete transparency.
Best Practices for House Extension Cost Management
- Plan thoroughly before construction begins
- Choose reliable, vetted professionals like Kova Interiors
- Regularly review budgets and timelines during construction
Final Thoughts
A well-planned house extension relies on understanding typical UK costs, factoring in regional differences, and building a realistic budget from the outset. Considering all expenses from design and permissions to construction and finishing ensures there are no unwelcome surprises along the way.
Careful budgeting and thorough planning not only keep your project on track but also protect your investment and deliver a high-quality finish. By working with an experienced, all-in-one professional team like Kova Interiors, you gain cost certainty, clear timelines, and a smooth process from concept to completion.
FAQs
How much does a typical house extension cost per square metre in the UK?
On average, a single-storey extension costs £1,500–£2,500 per m², while a double-storey costs £2,000–£3,000 per m². Kitchen extensions tend to be higher due to additional fittings and services.
Do house extensions increase property value?
Yes. A well-planned extension can increase property value by 10–20% or more, depending on the location, size, and quality of the build.
How long does it usually take to build a house extension?
A single-storey extension typically takes 8–16 weeks, while a double-storey can take 12–24 weeks, depending on complexity and site conditions.
Do I need planning permission for my house extension?
Not always. Some extensions fall under permitted development rights, but larger or more complex designs may require full planning permission.
What is the cheapest way to extend my house?
Opt for a simple single-storey layout, use cost-effective materials, and avoid major structural changes to keep costs down.