A Complete Guide, created in 2025 by Build Joy Ltd
Planning a House Extension in London?
One of the biggest questions homeowners face is:
How much will it really cost — and how does location affect price?
In 2025, London’s construction market continues to show stark differences in pricing across boroughs and neighbourhoods.
In this guide, we compare costs for House Extensions Ealing (Outer West London) vs Central London to give you a realistic picture before you build.
Why Location Matters for House Extension Costs
House extension costs vary widely across London due to differences in:
- Labour and contractor rates
- Site access and logistical challenges
- Ground conditions
- Planning and conservation constraints
Inner and central London areas (like Westminster, Camden, Kensington & Chelsea) generally command higher build costs due to expensive labour, delivery logistics, and stricter planning contexts.
Outer London boroughs — including Ealing & West London — tend to have lower build costs, often around 25 % cheaper in raw construction pricing.
Typical House Extension Costs in London (2025)
Central London Cost Benchmarks
In central London, industry guidance shows:
- Single‑storey house extension: £2,000 – £4,000 per m² for mid‑range construction
- Average London build estimate: £2,000 – £3,500 per m² overall
- UK home extension cost (national average): ~£2,885 per m², with London typically higher than the UK average
Example: A 30 m² single‑storey kitchen/dining House Extension in Central London might cost roughly £60,000 – £125,000 before VAT and professional fees.
Estimated Ealing House Extension Costs (2025)
Ealing is part of Outer West London, where costs are generally less than in central zones due to easier access, lower labour surcharges, and reduced logistical complexity.
To help you compare, we’ll assume a 25 % cost reduction on typical central London rates (a realistic estimate based on regional labour/materials differences).
That gives:
- Ealing single‑storey House Extension: approx. £1,500 – £2,500 per m² (20 % less than central London)
- Ealing Extension total cost for 30 m²: ~£45,000 – £75,000 pre‑VAT & fees
This reduction reflects more affordable contractor pricing and lower site complexity compared to central zones — although exact costs can vary based on builder quotes, specifications, and finish quality.
Detailed Cost Comparison: Ealing vs Central London
| Category | Central London (2025) | Ealing Estimated (2025) |
| Single‑storey extension (per m²) | £2,000 – £4,000 | £1,500 – £2,500 est. |
| Typical 30 m² total cost | £60,000 – £125,000 | £45,000 – £75,000 est. |
| VAT (20%) | Added on top of the construction | Added on top of the construction |
| Professional fees | 15 – 25 % typical | 15 – 25 % typical |
| Basement extension | £5,000 – £7,000 per m² | ~£4,000 – £5,600 est. |
This table shows how home extensions Ealing can offer significant savings over central London while delivering similar quality and outcomes for many homeowners.
What’s Included in Your Extension Budget
Regardless of the London location, your cost estimate should consider:
- Construction & Materials
Builders’ labour, structural work, foundations, and finishes. This forms the core of your budget. - Professional Fees
Architects, structural engineers, party wall surveyors, and planning consultants typically add 15 – 25 % extra. - VAT & Planning Fees
VAT (20 %) applies to most builds, and planning permissions London currently cost around £528. - Additional Features
Integrating kitchens, bathrooms, or high‑end fixtures will increase the cost significantly.
Factors That Affect Price Across London Areas
Whether in Ealing or central London, these common factors influence your final cost:
- Site access and space constraints — tighter sites are costlier
- Ground conditions — poor soil or basements increase excavation costs
- Finish quality — bespoke features, bespoke glazing or high‑end finishes add to price
- Planning & conservation requirements — historic or restricted properties often incur extra fees
Typical Project Scenarios (2025 Estimates)
Single‑Storey Rear Extensions (30 m²)
- Central London: ~£60,000 – £105,000
- Ealing (25 % less): ~£45,000 – £75,000
Double‑Storey House Extensions (40 m² equivalent)
- Central London: ~ Starting from £100,000 onwards
- Ealing: ~Starting from £60,000 onwards
These figures help you set realistic budgets based on typical London scenarios.
Timeline & Budgeting Tips
- Build times: Most single‑storey extensions take ~8–14 weeks, while larger projects can last several months
- Contingency: Always set aside a 10–15 % contingency for unexpected costs
- Get multiple quotes: Shop several builders and architects before committing
Summary: Ealing vs Central London
- House extension costs in London vary significantly by location and build complexity
- Central London costs are typically higher due to labour and logistical premiums
- House extensions Ealing — part of Outer West London — can be roughly 25 % cheaper on comparable extensions
- Base London extension costs per m² typically fall between £2,000–£4,000+, depending on design and finish
Frequently Asked Questions
Question: Should I expect the same planning process in Ealing and central London?
Answer: Yes, planning permissions London and building regulations are consistent across London boroughs, though local conservation requirements may vary
Question: Can VAT be reduced on home extensions?
Answer: Standard VAT is 20 %, but some specific renovations or conditions may offer exemptions — check with your contractor or tax advisor
Question: Is a house extension worth it?
Answer: Well‑planned home extensions Ealing usually add considerable value to properties — often more than the build cost, especially in London markets
Question: What is the step-by-step process to engage Build Joy Limited?
Answer: These are the steps clearly laid out:
Step 1: Initial Appointment & Project Discussion
Start by contacting Build Joy to book your free initial consultation
During this meeting:
- You’ll discuss your goals, budget, and type of extension (e.g., rear, side-return, double-storey house extensions Feltham)
- A feasibility assessment will be conducted based on your property and planning constraints
- Small deposit paid to secure Build Joy as Design & Build Consultant
- Apart from architecture fees, all deposits are Refundable if planning is not approved by the council
Tip: Prepare rough measurements, photos, and any inspiration ideas you have
Step 2: Design Proposal & Fees
After the consultation:
- Build Joy provides a formal design proposal tailored to your needs
- Once you approve the scope, you pay the design and planning fees to proceed with architectural drawings
These fees typically cover:
- Measured site surveys
- Existing and proposed floor plans
- Planning strategy
No strategy will guarantee planning, as the same is subject to approval by local councils
Step 3: Planning Application Submission
Once your design is finalised:
- Build Joy submits your planning application to your local council (e.g., Ealing Council or City of Westminster)
- They handle all necessary documentation, forms, and liaison with planning officers
- You’ll receive updates on progress, feedback, or requested amendments
- Any additional requirements raised by council will be advised and if any extra charges required for engaging consultants will be advised
Planning decisions typically take 8 to 12 weeks from submission. (Delays happen)
Step 4: Building Regulations Drawings & Structural Design
After planning approval:
- Detailed Building Regulations drawings are created, covering:
- Structural plans
- Construction details
- Drainage layouts
- Insulation and compliance
These are used for:
- Building Control approval
- Accurate costings
- Construction execution
Structural engineer input is also included at this stage
Step 5: Construction Begins
Once approvals are in place:
- Build Joy will begin on-site construction based on agreed timelines and staged payments
- Project management is included to ensure quality control, progress tracking, and on-budget delivery
