Full-insulated garden studio
Wandsworth · Screw pile · 5-week build
Brief
Client needed a full-time home office separate from the main house after Covid hybrid working became permanent. A 20m² insulated studio with oak cladding, roof lantern, underfloor heating and gigabit data was designed to function as a professional workspace year-round.
Challenge
A large Norway Spruce 8m from the proposed build site required a BS 5837 arborist survey before any groundworks could proceed. The tree survey established a root protection zone that ruled out conventional concrete strip foundations. The project also required a Lawful Development Certificate confirming Class E permitted development compliance before works commenced.
Solution
Screw pile foundations were installed at 300mm clearance from the outer edge of the root protection zone — no excavation, no root severance, same-day installation. Warmcel 100mm blown-in cellulose insulation filled the 140mm stud walls; oak featherboard cladding in Thermowood finish was fixed over a ventilated cavity; a Velux QPF pivot roof lantern was installed over the central working area. UFH screed provides 250W/m² heating capacity. The underground power run used 10mm² SWA armoured cable at 500mm depth alongside Cat6 gigabit data in conduit.
Outcome
The completed 20m² studio achieves an overall fabric performance of 0.18 W/m²K — better than Part L minimum. The Lawful Development Certificate was obtained prior to works commencing, giving the client a clean legal record. The client rated Builderr 5-star specifically for planning navigation and programme certainty, and moved into the studio on day 35.
Spec
Project specification.
Gallery
Inside the build.
"Builderr handled everything — the tree survey, the LDC, the underground power. We moved in on day 35. Exceptional."
— Sarah M., Balham
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 £7,700–£17,325 on a garden office.
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 £38,500.
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