Side-Return Extension, Wandsworth Edwardian Terrace
A dark galley kitchen opened into a 32 sqm kitchen-diner with a structural rooflight and full-width garden link.
Brief
An Edwardian terrace with a tight 1.4m side return and a dark galley kitchen that the family had outgrown. The owners wanted an open kitchen-diner with a strong visual link to the garden, generous daylight, and a flow that worked for two young children and weekend hosting.
Challenge
Two separate party wall awards were required, one with a precious neighbour who had recently completed their own works. The new foundations sat squarely inside the root protection zone of a mature lime tree on the boundary, and the local tree officer would not allow conventional strip footings within 3m of the trunk.
Solution
We engineered piled foundations 3m deep on a CFA mini-pile rig, threading between the lime's structural roots under a method statement signed off by an arboriculturist. A steel goalpost frame carries the rear opening for 5m x 2.5m sliding doors, with an 8m structural rooflight running the length of the new party wall. Herringbone oak ties the new kitchen-diner back to the original hallway.
Outcome
Both party wall awards were agreed amicably with no surveyor disputes, the RIBA-accredited structural engineer signed off the piles and steels first visit, and the project landed on budget. A 4-day overrun on the rooflight delivery was absorbed inside the programme float without affecting the handover date.
Spec
Project specification.
Gallery
Inside the build.
"The piled foundations under the lime tree could have been a nightmare, but Builderr managed the arboriculturist, the tree officer and both neighbours so calmly that we barely noticed. We came home one Friday and the back of the house had simply become twice the room it used to be."
— Priya and James Okafor, Wandsworth SW18
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 £19,000–£42,750 on a side-return extension.
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 £95,000.
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