Garden-linked basement conversion
Kensington · Stucco-fronted terrace · 26-week build
Brief
A Grade II-listed stucco terrace in SW7 with a tired garden-level layout and zero basement. The owners wanted a media room, gym, plant room and a guest suite — without losing the protected front elevation.
Challenge
Listed building consent plus full planning under a Tier 1 RBKC basement policy. Underpinning the party walls of two adjoining listed terraces required two party wall awards and a structural engineer signed off by the borough. Daylight at 5m below ground level via a single rear lightwell.
Solution
Sequential underpinning in 1m pins under building control hold-point inspection. 8m glazed garden link as the basement's natural ceiling at the rear, with a steel goalpost frame transferring loads off the rear closet wing. Cinema room acoustically isolated with floating floor on neoprene pads. Sump pumps duplicated with battery backup. Plant room consolidated to a single technical wall.
Outcome
Listed building + planning consents at 18 weeks, party wall awards at week 22. Site build 26 weeks against 30-week programme. Resale agent valued the uplift at £950,000 against £410,000 spend.
Spec
Project specification.
Gallery
Inside the build.
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 £82,000–£184,500 on a basement conversion.
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 £410,000.
Want a build like Kensington & Chelsea?
Get a fixed-scope quote with the same direct-labour delivery. Senior consultant call within one business hour.
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