Types We Estimate
Every Extension Type Covered
We estimate all house extension types — from a simple single storey kitchen extension to a full basement dig. Click any type to see costs, suitability, and what's included.
Indicative Cost Range
£35,000–£90,000
Exc. VAT · 12–18 weeks
Single Storey Rear Extension
Most popular extension
The most common house extension in the UK — extending the rear ground floor to create a larger kitchen, dining room, or open-plan living space. Works on virtually every house type.
Best Suited For
- Terraced, semi-detached & detached houses
- Kitchen-diner extensions
- Open-plan living spaces
Estimate Includes
- Groundworks & foundations
- Structural frame & walls
- Flat or pitched roof
- Bifold/sliding doors & glazing
- Internal fit-out & finishes
Most single storey rear extensions fall under Permitted Development (up to 4m for detached, 3m for others). Larger extensions may need planning permission.
Standard
Standard£1,500–£2,000/m²
- Concrete block cavity walls
- Flat EPDM roof
- uPVC or aluminium doors
- Basic kitchen (£8k–£12k)
- Carpet or LVT flooring
Mid-Range
Mid-Range£2,000–£2,800/m²
- Brick or render exterior
- Flat roof with rooflight
- Aluminium bifold doors
- Mid-range kitchen (£15k–£25k)
- Engineered oak or tiled floor
Premium
Premium£2,800–£4,500+/m²
- Architectural glazing & steel
- Roof lantern or glass roof
- Bespoke sliding / pivot doors
- Bespoke kitchen (£30k–£60k+)
- Underfloor heating + porcelain
Typical Project Budgets
Single Storey Rear (Standard)
Standard20 m² · Terrace / Semi
Flat roof, bifold doors, basic kitchen extension, Midlands baseline
Single Storey Rear (Premium)
Premium30 m² · Detached
Roof lantern, underfloor heating, bespoke kitchen, London pricing
Double Storey Rear
Mid-Range40 m² GIA · Semi-Detached
Kitchen-diner below, bedroom + en-suite above, Midlands baseline
Wrap-Around (London)
Premium45 m² · Victorian Semi
Full rear + side return, open-plan, roof lantern, London pricing (+35%)
Unit Rate Breakdown
| Element | Unit | Standard | Mid-Range |
|---|---|---|---|
| Groundworks & Strip Foundations | per m² | £120–£180 | £160–£260 |
| Structural Steelwork (RSJs) | per beam | £700–£1,400 | £1,100–£2,200 |
| Blockwork Cavity Walls | per m² | £90–£140 | £130–£200 |
| Flat Roof (EPDM / GRP) | per m² | £80–£130 | £110–£180 |
| Pitched Roof (tiled) | per m² | £110–£170 | £150–£240 |
| Roof Lantern / Rooflight | each | £1,800–£3,500 | £3,000–£6,000 |
| Bifold Doors (3-panel) | per set | £3,500–£6,000 | £5,500–£10,000 |
| Sliding Doors (2-panel) | per set | £2,800–£5,000 | £4,500–£8,500 |
| Underfloor Heating (wet) | per m² | £55–£90 | £80–£140 |
| Insulated Concrete Floor Slab | per m² | £65–£95 | £85–£130 |
| Plasterboard & Skim (walls) | per m² | £28–£45 | £40–£65 |
| Electrical First & Second Fix | per m² | £45–£75 | £65–£110 |
| Plumbing (extension only) | per m² | £35–£60 | £55–£90 |
| Kitchen Supply & Fit | per project | £8,000–£18,000 | £16,000–£40,000 |
| Decoration (walls & ceiling) | per m² | £12–£20 | £18–£30 |
Important: All figures are indicative and exclude VAT (20%), planning fees, building regulations fees, structural engineer fees, and party wall surveyor costs. London and South East costs are typically 20–35% higher. Always commission a professional estimate before committing to a budget.
Regional Cost Multipliers
London
×1.35
35% above Midlands baseline
South East
×1.18
18% above baseline
South West
×1.05
5% above baseline
East of England
×1.10
10% above baseline
Midlands
×1.00
Baseline region
North West
×0.95
5% below baseline
Yorkshire
×0.92
8% below baseline
North East
×0.88
12% below baseline
Wales
×0.90
10% below baseline
Scotland
×0.93
7% below baseline
Need a project-specific extension estimate?
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How It Works
Drawings to Estimate in 24 Hours
A straightforward four-step process — from sending us your drawings to having a professional estimate in your inbox.
Why Choose Us
Why Homeowners & Developers Trust Us
38 Years Experience
Our estimators have been pricing house extensions since before most online calculators existed. Real experience, real accuracy — not algorithm-generated guesses.
Regional Cost Data
We maintain live cost databases for every UK region. Your estimate reflects your actual local market — not a national average that could be 35% out.
Excel & PDF Delivery
Every estimate is delivered in both Excel (editable) and PDF format. Share with contractors, architects, or your mortgage lender with confidence.
24-Hour Turnaround
We quote within 1 hour and deliver the full estimate within 24 hours. No waiting weeks for a number you could have had tomorrow morning.
Fixed Fee, No Surprises
You know exactly what you're paying before we start. No hourly rates, no hidden extras — just a clear fixed fee for a professional estimate.
All Extension Types
Single storey, double storey, side return, wrap-around, over-garage, basement — we estimate every extension type to the same high standard.
Planning Permission & Building Regulations
Many house extensions fall under Permitted Development rights and don't require planning permission — but size, location, and property type all affect this. All extensions require Building Regulations approval regardless of planning status. Party Wall Act notices are required where work affects a shared wall.
House extension costs in the UK range from £35,000–£55,000 for a basic single storey rear extension up to £400,000+ for a full basement in London. The most common type — a single storey rear extension at mid-range specification — typically costs £1,800–£2,500 per square metre in the Midlands and North. London and South East costs are typically 20–35% higher. Always get a professional estimate before committing to a budget.