Southwark · London
Rear Extension in Southwark
Mix of Georgian terraces and post-war flats — loft and side return work common.
Southwark
Rear Extension specialists across Southwark.
We deliver rear extension projects across the full Southwark postcode set — SE1, SE5, SE15, SE16, SE17, SE21, SE22. Mix of Georgian terraces and post-war flats — loft and side return work 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 Southwark 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 Southwark 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 Southwark.
Familiarity with Southwark's planning officers, party wall surveyors and approved inspectors cuts weeks off the approval timeline. We deliver consistent quality across all 7 postcodes the borough covers.
Recent Southwark 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 Southwark.
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 Southwark.
How much does a rear extension cost in Southwark?+
Rear Extension projects in Southwark typically cost £50,000–£130,000. Southwark sits across postcodes SE1, SE5, SE15, SE16; local rates align with the wider London market.
Do rear extensions in Southwark need planning permission?+
Mix of Georgian terraces and post-war flats — loft and side return work 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 Southwark postcodes?+
Yes — we deliver rear extension projects across all Southwark postcodes including SE1, SE5, SE15, SE16, SE17, SE21, SE22.
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 Southwark rear extension quote.
Senior consultant call within one business hour. Fixed-scope quote for your Southwark project — no provisional sums.
Other types in Southwark
Explore other build types in Southwark.
Rear Extension across London