Merton · London
Rear Extension in Merton
South-west borough including Wimbledon — premium extensions and full refurbs common.
Merton
Rear Extension specialists across Merton.
We deliver rear extension projects across the full Merton postcode set — SW19, SW20, CR4, SM4. South-west borough including Wimbledon — premium extensions and full refurbs common.
A rear extension projects from the back of the house into the garden, creating open-plan living, a new kitchen or a family room. Single-storey rears can extend up to 6 metres on detached homes and 8m by prior approval under the Larger Home Extension scheme. They suit terraces, semis and detached houses across London and remain the most popular extension type by volume.
Every Merton project includes a free desk-based planning assessment before we quote. We know the local planning officers, party wall surveyors and approved inspectors by name.
Costs
Rear Extension cost in Merton 2026.
| Configuration | Cost range | Timeline |
|---|---|---|
| Single-storey rear (3m deep) | £50,000–£75,000 | 10–12 wks |
| Single-storey rear (5–6m deep) | £70,000–£100,000 | 12–14 wks |
| Rear + kitchen install | £85,000–£120,000 | 13–16 wks |
| Premium rear (structural glass, Crittall) | £105,000–£130,000 | 14–18 wks |
Local advantage
Eight years of rear extension work in Merton.
Familiarity with Merton's planning officers, party wall surveyors and approved inspectors cuts weeks off the approval timeline. We deliver consistent quality across all 4 postcodes the borough covers.
Recent Merton work
Rear Extension examples.
Builderr vs other London builders.
The construction industry has a wide distribution of operators. Here's what changes between a directly-employed, fixed-scope outfit and the alternatives.
| Criterion | Builderr | Typical London builder | Cowboy outfit |
|---|---|---|---|
| Labour model | Directly employed team (PAYE) | Mixed subcontract gangs | Day-rate cash labour |
| Pricing | Fixed-scope itemised quote | Estimate + provisional sums | Verbal price + variations |
| Design & engineering | In-house architect + SE | Outsourced, separate billing | Builder draws on the back of an envelope |
| Planning + LDC handled | Yes — included in price | Often charged extra | Builder asks you to apply |
| Party wall surveyors | Instructed by us | Your responsibility | Skipped (illegal) |
| Building control | Plans + site inspections booked by us | Building Notice route | Not registered |
| Project management | Dedicated PM, weekly photo updates | Foreman doubles up | Owner-manager juggles 5 jobs |
| Payment schedule | Stage payments against signed-off milestones | Weekly invoices | Cash up front |
| Insurance | £10M PL + 10yr structural warranty | £2–5M PL only | No documented cover |
| Snags at handover | <3 typical | 20–30 typical | Walk-off mid-job common |
| Variation creep | 0% — fixed scope | +15–25% over original quote | +40%+ regularly |
Save £18,000–£40,500 on a rear extension in Merton.
Industry data (FMB, RICS, Which? Trusted Trader 2024) shows the average London construction project overruns by 18–22% on cost and 25–35% on time. Fixed-scope contracts with a single accountable team eliminate that variance. The savings above assume a typical project at £90,000.
FAQ
Rear Extension in Merton.
How much does a rear extension cost in Merton?+
Rear Extension projects in Merton typically cost £50,000–£130,000. Merton sits across postcodes SW19, SW20, CR4, SM4; local rates align with the wider London market.
Do rear extensions in Merton need planning permission?+
South-west borough including Wimbledon — premium extensions and full refurbs common. We carry out a free desk-based planning assessment for your specific address before quoting, identifying whether permitted development, prior approval, or full planning applies.
Do you work across all Merton postcodes?+
Yes — we deliver rear extension projects across all Merton postcodes including SW19, SW20, CR4, SM4.
How much does a rear extension cost in London?+
Typically £50,000–£130,000 depending on depth, glazing spec, kitchen inclusion and any structural complications.
Do I need planning permission?+
3m deep and under is permitted development. 3m–6m on a terrace or semi requires prior approval under the Larger Home Extension scheme. Beyond that or in conservation areas, full planning.
Get a Merton rear extension quote.
Senior consultant call within one business hour. Fixed-scope quote for your Merton project — no provisional sums.
Other types in Merton
Explore other build types in Merton.
Rear Extension across London