Planning a home extension is one of the most effective ways to add space and value to your property. Understanding the house extension cost per square foot is essential for setting a realistic budget. This guide breaks down average pricing across the UK, regional variations, labour and material costs, and the factors that influence your final bill – helping you plan with confidence and avoid costly surprises.
The cost of house extension per square foot depends primarily on the specification level you choose. Below is a summary of estimated market averages based on contractor quotations and industry research across the UK. These figures represent a general guide; actual costs will vary by project.
| Build Quality | Cost Per Sq Ft (Approx) | Cost Per Sq Metre (Approx) | Typical Features |
|---|---|---|---|
| Basic / Budget | £110 – £150 | £1,200 – £1,600 | Standard materials, simple roof, basic fixtures |
| Mid-Range | £150 – £200 | £1,600 – £2,150 | Good-quality materials, bi-fold doors, underfloor heating |
| High-Spec / Luxury | £200 – £300+ | £2,150 – £3,200+ | Premium finishes, bespoke glazing, architect-designed |
Note: These estimates are market averages and may not reflect every project. Always obtain multiple quotations tailored to your specific requirements.
Understanding where your money goes helps you budget more effectively. The table below shows a typical approx cost house extension per square foot breakdown for a mid-range single-storey extension.
| Cost Component | Percentage of Total | Estimated Cost (per sq ft) |
|---|---|---|
| Labour (builders, electricians, plumbers) | 40% – 50% | £60 – £90 |
| Materials (bricks, timber, insulation, roofing) | 30% – 35% | £45 – £65 |
| Fixtures & Fittings (windows, doors, sanitaryware) | 10% – 15% | £15 – £28 |
| Professional Fees (architect, structural engineer) | 5% – 8% | £7 – £15 |
| Waste Removal & Site Clearance | 2% – 4% | £3 – £7 |
| VAT (if applicable at 20%) | Add 20% | £22 – £46 |
VAT Note: Many contractor quotations exclude VAT. Always confirm whether VAT is included. The standard VAT rate is 20%, though some extension projects may qualify for reduced-rate VAT under specific conditions. Seek professional tax advice if unsure.
The UK house extension cost per square foot varies considerably by region. Labour rates in London and the South East are significantly higher than in the North of England, Scotland, or Wales.
| Region | Average Cost Per Sq Ft | Relative to UK Average |
|---|---|---|
| London | £180 – £300 | +20% to +30% |
| South East | £160 – £260 | +10% to +20% |
| Midlands | £130 – £200 | Near UK average |
| North England | £110 – £175 | -5% to -15% |
| Scotland | £100 – £200 | Varies by city vs rural |
| Wales | £105 – £170 | -5% to -15% |
| Northern Ireland | £100 – £165 | -5% to -20% |
For house extensions Scotland cost per square foot, Glasgow and Edinburgh are at the higher end (£150–£200 per sq ft), while rural Highland projects may come in lower on labour but face increased material delivery charges.
Different types of extensions carry different cost profiles. Here is how the cost per square foot to build a house extension compares across common project types:
| Extension Type | Cost Per Sq Ft (Approx) | Typical Total Cost (20 sqm / 215 sq ft) |
|---|---|---|
| Single-Storey Rear Extension | £110 – £180 | £23,650 – £38,700 |
| Double-Storey Extension | £130 – £230 | £27,950 – £49,450 |
| Side Return Extension | £140 – £220 | £30,100 – £47,300 |
| Wrap-Around Extension | £150 – £250 | £32,250 – £53,750 |
| Kitchen Extension | £160 – £280 | £34,400 – £60,200 |
Several variables affect the final cost house extension per square foot figure. Being aware of these can help you control your budget:
A common question is whether it is more economical to build out or up. A single-storey extension generally has a lower average cost of house extension per square foot because foundations and roofing are simpler. However, a double-storey extension shares the foundation and roof cost across two floors, which can make it more cost-effective per square foot of total space gained. If you need substantial extra room, going double-storey often delivers better long-term value.
Below are three realistic house extension cost per square foot examples based on typical UK projects. These are estimated market averages for illustration purposes.
| Project | Size | Build Quality | Estimated Labour | Estimated Total Cost |
|---|---|---|---|---|
| Small Single-Storey Rear Extension | 15 sqm (161 sq ft) | Mid-Range | £9,500 – £14,000 | £22,500 – £32,000 |
| Medium Kitchen-Diner Extension | 25 sqm (269 sq ft) | Mid-Range | £16,000 – £23,000 | £38,000 – £54,000 |
| Large Double-Storey Side & Rear | 45 sqm (484 sq ft) | High-Spec | £29,000 – £42,000 | £75,000 – £110,000 |
Our pricing estimates are based on a combination of UK contractor quotations, supplier pricing catalogues, regional labour rate comparisons, and industry market research. We consider average labour rates, material pricing, regional differences, project complexity, and historical market trends. These figures are intended as a practical budgeting guide and represent estimated market averages rather than official statistics.
The pricing information in this article has been compiled using:
Where official data is unavailable, we clearly state that figures are estimated market averages. No proprietary or confidential data has been used, and no official government statistics have been fabricated.
The average house extension cost per square foot in the UK ranges from approximately £110 to £230, depending on build quality, location, and extension type. A basic single-storey extension may cost around £110–£150 per sq ft, while a high-specification double-storey extension can reach £200–£300+ per sq ft.
In Scotland, house extension costs per square foot typically range from £100 to £200. Glasgow and Edinburgh tend to be at the higher end due to labour demand, while rural areas and the Highlands may offer slightly lower labour rates but higher material delivery costs.
Not always. Many contractor quotations exclude VAT, which is charged at the standard rate of 20% in the UK. Always confirm with your builder whether their quote includes VAT before accepting. Some extension projects may qualify for reduced-rate VAT under certain conditions.
A single-storey extension typically takes 8–14 weeks from groundworks to completion. A double-storey extension may take 12–20 weeks. Factors such as planning permission, weather conditions, and material availability can affect the overall timeline.
Key factors include: extension type (single vs double storey), build quality (basic, mid-range, high-spec), ground conditions, access to the site, regional labour rates, material choices, kitchen or bathroom fittings if included, glazing specifications, and whether planning permission is required.
Building out (a single-storey extension) is generally cheaper per square foot than building up (a double-storey extension) because of simpler foundations and less structural steelwork. However, a double-storey extension can be more cost-effective overall if you need significant additional space, as the cost of foundations and the roof is shared across two floors.
To save money: obtain at least three competitive quotations, consider a simpler roof design, use standard-sized doors and windows, manage the project yourself if experienced, source materials independently, and avoid changing the specification mid-project. Always budget a 10–15% contingency fund for unexpected costs.