Westminster · London
Side Return Extension in Westminster
Central borough with listed and conservation stock — interior and basement work dominates.
Westminster
Side Return Extension specialists across Westminster.
We deliver side return extension projects across the full Westminster postcode set — W1, SW1, NW1, NW8. Central borough with listed and conservation stock — interior and basement work dominates.
A side return extension fills the narrow alleyway running alongside the rear closet wing on Victorian and Edwardian terraces. By extending out to the boundary wall, the kitchen gains 3–4 metres of additional width and connects to the garden through a glazed rear wall. It's the most common ground-floor extension in London — over 60% of inner-London terraced extensions are side returns — because it unlocks a generous open-plan kitchen-diner without losing garden depth.
Every Westminster 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
Side Return Extension cost in Westminster 2026.
| Configuration | Cost range | Timeline |
|---|---|---|
| Standard side return (3m wide, full glazed rear) | £55,000–£75,000 | 10–12 wks |
| Side return with steel beams + roof lantern | £70,000–£90,000 | 11–14 wks |
| Side return + kitchen install | £85,000–£110,000 | 12–15 wks |
| Premium side return (Crittall, structural glass) | £100,000–£120,000 | 13–16 wks |
Local advantage
Eight years of side return extension work in Westminster.
Familiarity with Westminster'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 Westminster work
Side Return 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 £17,500–£39,375 on a side return extension in Westminster.
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 £87,500.
FAQ
Side Return Extension in Westminster.
How much does a side return extension cost in Westminster?+
Side Return Extension projects in Westminster typically cost £55,000–£120,000. Westminster sits across postcodes W1, SW1, NW1, NW8; local rates align with the wider London market.
Do side return extensions in Westminster need planning permission?+
Central borough with listed and conservation stock — interior and basement work dominates. 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 Westminster postcodes?+
Yes — we deliver side return extension projects across all Westminster postcodes including W1, SW1, NW1, NW8.
How much does a side return extension cost in London?+
Typically £55,000–£120,000 depending on size, glazing spec and kitchen inclusion. A 3m × 4m side return without kitchen runs around £60–80k; with premium kitchen and Crittall glazing closer to £110k+.
Do I need planning permission for a side return?+
Most fall under permitted development. Conservation areas and Article 4 zones usually need full planning. We screen this on every quote.
Get a Westminster side return extension quote.
Senior consultant call within one business hour. Fixed-scope quote for your Westminster project — no provisional sums.
Other types in Westminster
Explore other build types in Westminster.
Side Return Extension across London