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Understand the true costs before you start — from per m² rates to council quirks and regional differences.
Extension Costs • UK Rules & Local Quirks
Single Storey Extension Costs Explained
How much does a single storey extension cost in the UK? On average, homeowners pay £1,800 – £3,000 per m², but prices vary by location, complexity and finish. A small single storey extension might cost around £45,000, while larger wrap-around projects in London can exceed £90,000. This guide breaks down costs, council quirks and what to expect.
Quick Answer: What Does a Single Storey Extension Cost?
If you’re looking for a ballpark figure: most single storey extensions fall between £45,000 and £75,000. Smaller builds cost less, while complex wrap-arounds in London or the South East push higher. The Planning Portal and GOV.UK guidance are useful for official advice, but here we focus on real-world costs.
Key Factors That Affect Cost
- Size — measured in m² (the bigger the footprint, the higher the total cost).
- Type — rear, side, or wrap-around (wrap-arounds usually require more structural steel).
- Location — London typically costs 20–30% more than the North West or Midlands.
- Spec & Finish — bi-fold doors, rooflights, and high-end kitchens increase spend.
- Council quirks — different planning and building control fees across the UK.
Typical Cost Breakdown (per m²)
| Extension Type | Low Range (£/m²) | High Range (£/m²) | Typical Total Cost |
|---|---|---|---|
| Rear single storey | £1,800 | £2,400 | £45,000 – £65,000 |
| Side single storey | £1,900 | £2,600 | £50,000 – £70,000 |
| Wrap-around single storey | £2,200 | £3,000+ | £65,000 – £90,000+ |
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Regional & Council Quirks
One of the biggest cost variables is location:
- London & South East: 20–30% higher build costs due to labour and material rates.
- North West & Manchester: Some of the lowest average extension prices in England.
- Scotland: Costs per m² can be slightly lower, but planning requirements differ — always check with the local council.
Extra Costs to Budget For
- Planning application fees (if required)
- Building control submission & inspections
- Party wall surveyor (if near a boundary)
- Structural engineer for steel design (common in wrap-arounds)
- Professional drawings and design fees
- VAT — unless your builder is not VAT registered
Conclusion
A single storey extension is one of the best ways to add space and value to a home, but costs vary widely. Use the ranges above as a guide, check regional quirks, and always allow a buffer for hidden expenses. For tailored advice, it’s wise to get plans drawn and reviewed early — avoiding costly surprises later.
FAQs: Single Storey Extension Costs
How much does a single storey extension cost UK?
On average, expect £1,800 – £3,000 per m². A small 20m² extension may cost £45,000, while larger wrap-around builds can exceed £90,000.
How much does a single storey extension cost in London?
London typically adds 20–30% to the UK average due to higher labour and material costs. A wrap-around may exceed £100,000.
Is it cheaper to build a rear or side extension?
Rear extensions are generally simpler and cheaper. Side extensions may need additional structural work, increasing costs slightly.
What extra costs should I expect beyond the build?
Professional fees (plans, building control), VAT, and potential party wall surveyor costs should be factored in.
Can I estimate my cost with a calculator?
Online calculators give a rough guide, but for accurate figures it’s best to commission drawings and get builder quotes based on them.
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