Thinking About Extending Your Home in West London?
Whether you need more space for a growing family, a larger kitchen, or a luxurious home office, a house extension can transform your property — and significantly boost its value. But before you break out the mood boards, let’s talk numbers.
So, how much does a house extension cost in West London in 2025? The answer depends on a few key factors, but we’ve broken it down to give you clarity, confidence, and a smart starting point.
Average House Extension Costs in West London (2025)
| Type of Extension | Estimated Cost Range | Cost per m² |
|---|---|---|
| Rear/Side Return Extension | £60,000 – £120,000 | £2,800 – £4,000/m² |
| Wraparound Extension | £100,000 – £180,000 | £3,000 – £4,200/m² |
| Double-Storey Extension | £120,000 – £220,000+ | £2,500 – £3,800/m² |
| Kitchen Extension (Mid-Range) | £70,000 – £110,000 | £3,200 – £4,000/m² |
| High-Spec Extension | £150,000+ | £4,000/m² and above |
What Affects the Cost of a House Extension?
Several factors impact your final price. Here’s what to consider:
1. Size & Layout
Naturally, the larger the footprint, the higher the cost. But complexity matters too — L-shaped, wraparounds, or double-storey designs often need more structural work.
2. Specification & Finish
Are you going high-end with polished concrete floors, bespoke cabinetry, and crittall doors? Expect to pay more than a standard spec.
3. Site Conditions
Access is a major player. If your home is in a tight terrace or conservation area (hello, Notting Hill), expect higher labour and logistics costs.
4. Planning & Regulations
Permitted development rights can reduce costs. But if you need full planning permission, party wall agreements, or deal with listed status, budget for added time and fees.
5. Build Method & Team
Using a design-and-build firm often brings efficiency — and fewer unexpected bills — than managing multiple contractors separately.
Realistic Cost Examples (West London Case Studies)
- Chiswick Rear Extension – £85,000
A 5m rear kitchen-diner with aluminium bi-folds and underfloor heating. Planning handled in-house. - Richmond Wraparound – £165,000
Open-plan living/kitchen/dining with utility room and steel-framed doors. Mid-to-high-end finish. - Ealing Double-Storey – £210,000
Ground-floor living extension with upstairs en-suite and office. Included complete garden redesign.
Will a House Extension Add Value?
In most parts of West London, the answer is a resounding yes — if it’s done right.
A well-designed extension can add:
- 20–25% to your property’s value in many boroughs
- £100,000+ in resale potential
- Huge lifestyle benefits, especially with flexible family space
Smart Tips to Keep Costs Under Control
- Start with a clear brief – Know what you need, not just what you want
- Choose a reputable local builder – Look for case studies, reviews, and clear communication
- Allow 10–15% contingency – Especially in older homes where surprises are likely
- Decide finishes early – Avoid mid-project upgrades (and cost creep)
- Avoid the cheapest quote – If it seems too good to be true, it probably is
