Hip-to-gable loft + rear dormer
Harrow · 1930s semi-detached · 10-week build
Brief
A growing family in Pinner (HA5) needed more bedroom space. Their 1930s semi-detached had a classic hip roof — ideal hip-to-gable territory — with a ridge height of 8.4m and a loft void of approximately 40m³. The brief: one large master bedroom with ensuite in the new loft space, converting the existing spare bedroom to a proper children's room.
Challenge
The 1930s semi-detached sits in the Pinner Conservation Area. Pinner is one of Harrow's most protected suburban neighbourhoods with strict CA design guidance requiring traditional materials on visible elevations. The gable build-up (hip to gable wall) needed to match the existing Sand-faced London stock brick precisely. The rear dormer required a zinc-clad finish to comply with CA guidance for non-street-facing additions.
Solution
We sourced reclaimed facing brick to match the existing gable brickwork — the new gable wall is indistinguishable from the original at street level. The rear dormer was clad in pre-weathered zinc (Rheinzink quartz zinc) to provide a clean, low-profile addition reading as a recessive rear extension. The structural hip-to-gable steel ran the full width of the roof in a single span (7.8m, 610mm UB). Planning submitted with photo-montage of the finished gable — approved in 9 weeks, zero amendments.
Outcome
The loft conversion added 28m² of habitable floor area — a 2.5m × 4.8m master bedroom with full standing headroom across 80% of the floor, plus a compact ensuite (1.4m × 2.2m) with rainfall shower. Conservation area approval achieved on first submission. Post-completion RICS valuation: property increased in value by £130,000 on a £72,000 build cost.
Spec
Project specification.
Gallery
Inside the build.
"The gable brickwork match is extraordinary — the neighbours thought we'd simply uncovered the original wall. Our planning officer actually complimented the design."
— Mark & Priya K., Pinner
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 £14,400–£32,400 on a hip-to-gable loft 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 £72,000.
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