Extending your home with a single-storey addition is a popular way to add valuable space without the hassle of moving. Many homeowners ask about the single storey extension cost and what affects the price for a single story extension.
In this article, you’ll learn:
- 2025 UK costs per m² for different build types (basic to high-end)
- Price examples based on extension size
- Key factors that influence single-storey extension costs
- Cost differences between rear, side, and garden room extensions
- What planning permission and building regulations apply
- Tips to budget your project and choose the right builder
- How ArkiPlan helps you get accurate quotes with professional drawings
Whether you’re considering a small rear extension or a larger garden room, understanding the average price for a single storey extension can help you plan your budget effectively.
What Is the Cost of a Single Storey Extension?
The single storey extension cost depends largely on the size of the extension, and is often calculated on a cost per square meter extension basis. Typically, prices range from around £1,800 to £4,000 per square meter depending on the quality of finishes and complexity of the project.
For example, a 20m² extension could cost anywhere between £36,000 and £80,000, depending on whether you opt for a basic, mid-range, or high-end build. Here’s an overview of typical costs in the UK:
| Build Quality | Cost per m² | Example (20m²) |
|---|---|---|
| Basic Build | £1,800 – £2,500 | £36,000 – £50,000 |
| Mid-Range Finish (most common) | £2,500 – £3,000 | £50,000 – £60,000 |
| High-End (kitchen/bathroom) | £3,000 – £4,000+ | £60,000 – £80,000+ |
If you want to know how much for a single story extension in London or the South East, expect prices to be 10–20% higher than the national average.
Factors Affecting Single Storey Extension Costs UK
When considering the cost of a single story extension, several factors influence the overall price:
- Size and layout of the extension
- Quality of materials and finishes
- Complexity of the build (roof type, foundations, etc.)
- Location and local labour costs
- Whether planning permission or building regulations apply
What Can You Do With a Single-Storey Extension?
A single-storey extension can significantly improve your home. The cost of a single story rear extension varies, but the benefits are clear:
- Expand your kitchen into a spacious kitchen-diner or family hub
- Add a utility room, boot room, or cloakroom
- Create a new garden room, studio, or quiet workspace
These options affect the price of a single story extension depending on design and specification.
At ArkiPlan, we design extensions that suit how you live. Our team ensures the new space flows with your home, complements your lifestyle, and adds long-term value.
Planning Permission and Building Regulations
Most single-storey extensions fall under permitted development, but it’s essential to check if your project meets the rules to avoid unexpected costs. If you need to apply, clear planning application drawings can help streamline the process.
Building regulations approval is usually required regardless of planning permission. This ensures your extension complies with structural safety, drainage, insulation, and ventilation standards.
Designing Your Extension With Arkiplan
Wondering about the price of a single story extension? At Arkiplan, all our drawings are done online—professionally and with your goals in mind. We focus on:
- How you live and what you need the space to do
- Layout, access, and impact on existing rooms
- Roof options like flat, mono-pitch, dual-pitch, or hipped roofs
- Glazing options for natural light, privacy, and energy efficiency
- Smart material choices and cost-effective finishes
We carefully consider your budget, planning limits, and future needs from the very first sketch.
How Much Does It Cost to Build a Single Storey Extension?
The cost to build single storey extension depends on construction quality and scope. Small extensions have lower small single story extension cost, while larger builds or complex designs increase the price.
On average, expect the cost per square meter extension to range between £1,800 and £4,000, with detailed building regulation plans helping to get accurate builder quotes.
Choosing the Right Builder
Selecting a builder experienced in single storey rear extension costs is crucial. We recommend:
- Checking builders with experience in single-storey extensions
- Reviewing references and past projects
- Requesting clear, itemised quotes aligned with our drawings
Our plans help reduce confusion and make quote comparisons easier. We’re also available to assist if your builder has questions.
Summary: How Much Does a Single Storey Extension Cost?
- Single storey extension price varies by size, location, and finish
- Typical costs range from £1,800 to £4,000 per m²
- Planning permission and building regulations can affect timing and cost
- A clear, detailed plan helps control extension cost and build quality
If you’re ready to know exactly how much does a single storey extension cost for your home, get in touch with ArkiPlan today. Our expert designers provide fast, accurate plans tailored to your needs and budget.